# could the Allison engine have done what the Rolls Royce Merlin did?



## CobberKane (May 8, 2013)

Okay, here's one for the technophiles (definitely not including me). The Allison engine in it's various guises has always seemed to play second fiddle to it's famous contemporary in the land of hope and glory, the Merlin. Was there any intrinsic design feature that precluded Allison engines from powering single engine fighters over Germany at 25000 feet, of was it all just a case of the American engine being hobbled by the thinking of the time - that high altitude fighters weren't required?
To get full marks, please include an objective comparison of the beers of both countries.

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## wuzak (May 8, 2013)

High altitude thinking = turbochargers

So no 2 stage until later, and no 2 speed supercharger (there may have been one prototype?).

In terms of supercharger development, Allison, like other US manufacturers, used GE designs to start with but got better results when they switched to designing their own.

Development was hamstrung by how much funding teh government wanted to pay, and an unwillingness to put money into new developments without a clear requirement and/or orders.

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## Shortround6 (May 8, 2013)

CobberKane said:


> Was there any intrinsic design feature that precluded Allison engines from powering single engine fighters over Germany at 25000 feet, of was it all just a case of the American engine being hobbled by the thinking of the time - that high altitude fighters weren't required?



This is often repeated but has little basis. 

The US wanted high altitude fighters, they were required. The USAAC had turbo P-30s, turbo Airacuda's. 13 YP-37s, the P-38 and P-39 prototypes. A turbo P-35 and a P-35 with a two stage supercharger plus a P-36/Hawk 75 with two stage supercharger were at the 1939 fighter trials that led to the P-40 order. 
The 1st problem was that NONE of the high altitude planes were really ready for SERVICE squadron use. 
The 2nd problem was that Allison was a very small company when it got the order for the engines to power the 500+ P-40s in the April 1939 order. Plant expansion and tooling up to make engines on a production line basis instead of tool room batches of a few engines per month meant that R&D on the high Altitude versions got put on the back burner (if not back in the refrigerator) until the production thing got sorted out. Production got even more complicated when Allison got permission to export the engine to France and Britain which meant an even higher production volume. 
3rd problem was that Allison had spent a bunch of time on other Army requirements like the P-39 remote propeller, the Airacuda remote pusher engine set up, the P-38 handed engine and the V-3420 double engine. 
GE was supposed to be handling the turbo for the high altitude planes. 
Army was handling the turbo controller? 
There is a recipe for success (not). 

other factors that hurt US fighter high altitude performance in the early part of the war were, 1. US fighters carried more fuel than _most_ other counties fighters. Given similar field requirements (landing and take-off) this means a bigger airplane, in general. 2. the US slapped a heavier armament into it's early aircraft (I am not saying better, I am saying heavier). 3. The US had a higher "G" limit than some other countries (not all) so the structural weight was higher. It adds up to planes that were hundreds of pounds heavier than their British or German equivalents in the early part of the war. Given roughly equivalent engines the US planes struggled at higher altitudes. 

Until Hooker came along the Merlin wasn't that much better at high altitudes. Once he showed up _everybody_ else was trying to play catch-up. 

Try slapping a Merlin III into a P-40C and see what kind of performance you get?

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## tomo pauk (May 8, 2013)

Great post, indeed.

There was no major hurdle to install the two stage V-1710 (the 'normal' drive equivalent of the E-11 installed in the P-63A) in the P-51 airframe and send it in the ETO in 1944. The altitude performance would not be on par with the Merlin Mustang, esp. vs. the early models with the high altitude V-1650-3, but it should be enough for a decent performance advantage vs. the LW opposition.
Another approach could've been the single engined fighter with turbo V-1710, something along the lines of the XP-60A (3 view). The plane based around that power-plant was feasible as early as P-38.


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## davebender (May 8, 2013)

This gets my vote. 

Same reason USA couldn't produce a reliable copy of Hs.404 20mm cannon even after Britain provided blueprints.


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## Shortround6 (May 8, 2013)

Do you have a reason for this? 

It gets printed in books and bandied about the internet but I don't believe I have ever seen any actual quotes or memo's about it. It usually comes down to people believing the nonsense performance figures for the XP-39 or thinking that Allison, who from 1930 to though 1938 built a total of 30 engines had the engineering staff and test facilities to design, build and deliver cutting edge supercharger technology when both Wright and P&W could not. 

The believers of this theory also ignore the the fact that the USAAC and Navy built and flew more turbo supercharged aircraft and more planes with two stage superchargers (most turbos) than the rest of the world put together before Sept 1939. 

A sure indicator of a lack of interest.

The US did a lot of dumb things, thinking that high altitude combat planes were not needed wasn't one of them.


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## Wavelength (May 8, 2013)

Its been awhile, but as I recall in the book about Schmued: Mustang Designer Schmued explains that when the Gov wanted them to use the Allison in the P51J and the F82, he finally diagnosed the problem of the Allison not liking boost to a flaw in the intake manifold design. He could not get GM to listen to him, however. The deafness wasn't Allison themselves but their coporate masters in Warren.

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## krieghund (May 11, 2013)

Kind of looks sexy


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## Readie (May 11, 2013)

krieghund said:


> Kind of looks sexy



It does....all that is missing is ROLLS ROYCE on the camcovers

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## Readie (May 11, 2013)

Seriously....

http://www.ww2aircraft.net/forum/engines/superchargers-early-v-1710-vs-merlin-17590.html

The answer is within this thread.

Cheers
John


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## tomo pauk (May 11, 2013)

Not sure it's there, John. What post did you have in mind? Seems there is no mentioning/analysis the 2-stage V-1710, nor the turbo variation.


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## dobbie (May 11, 2013)

The Allison could have made the high altitude horsepower with the proper supercharger set up, but no money was allocated for such a project until late in the war. I think the urgency of the war and production kept the redesign off the boards. As it was, Packard was already producing the Merlin under license, so possibly it was considered a waste of time. The Allison, even if the time and money would have been spent to develop to do so, wouldn't have made that much difference in performance which the Merlin already had. Wartime is a bad time for lengthy developments.

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## tomo pauk (May 11, 2013)

V-1710 actually made the 'high altitude horsepower,' rather early in the war. Earlier than the Merlin or DB-601.
As for 'difference in performance which the Merlin already had', maybe we should calculate in the airframe capabilities of the P-51 to get the whole picture?


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## dobbie (May 11, 2013)

tomo pauk said:


> V-1710 actually made the 'high altitude horsepower,' rather early in the war. Earlier than the Merlin or DB-601.



With a mechanical supercharger? Turbochargers are great, but then you end up with a monster sized fighter such as the P-47. Great aircraft, but a gas hog.


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## tomo pauk (May 11, 2013)

dobbie said:


> With a mechanical supercharger? Turbochargers are great, but then you end up with a monster sized fighter such as the P-47. Great aircraft, but a gas hog.



Why would one end up with a monster-sized fighter powered by a turbo V-1710?
The gas hog was patiently faster, more rugged and heavier armed than any fighter of ww2.


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## dobbie (May 11, 2013)

Don't get me wrong...."the gas hog" is my favorite! I suppose that if you made the fuselage long enough and wide enough to pack all of the plumbing necessary, you could have had something to show at high altitude. But that would take a clean sheet of paper to make it all work. Just like the P-47-it was designed around a turbocharged R2800. They did attempt the XP39 which didn't turn out so well, and the YP37 too.


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## Shortround6 (May 11, 2013)

The Allison would use the smaller "B" series turbo (P-47s used the "C"series) but you are right it would take more volume in the fuselage. What people keep forgetting is that the mechanical drive two stage supercharger just gets rid of the turbo and the exhaust plumbing. It still needs the second supercharger casing, a drive system and to be effective, an inter cooler and the associated plumbing/ducting to go with it. 

P-51B was 7 in deeper top to bottom than a a P-51A, in part to fit the Merlin and the intercooler/larger radiator and larger duct. 

An air/liquid intercooler is more compact than an air/air intercooler but adds another "system".

And it's volume is still not zero.

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## CobberKane (May 11, 2013)

tomo pauk said:


> The gas hog was patiently faster, more rugged and heavier armed than any fighter of ww2.



Possibly to number one, probably to number two, definitely not to number three.


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## tomo pauk (May 12, 2013)

It was carrying more weapon weight than any single-engined fighter, along with awfully big heavy ammo load. Anyway, my point is that one cannot get something for nothing. 
We might add the 1000 miles escort capability there, too.



dobbie said:


> Don't get me wrong...."the gas hog" is my favorite! I suppose that if you made the fuselage long enough and wide enough to pack all of the plumbing necessary, you could have had something to show at high altitude. But that would take a clean sheet of paper to make it all work. Just like the P-47-it was designed around a turbocharged R2800. They did attempt the XP39 which didn't turn out so well, and the YP37 too.



SR6 covered this. 
USA have had all what it takes to field the single-engined turbo V-1710 fighter contemporary with P-38, but the only firm that got layout correct (Republic), decided to go with R-1830 for their new fighter (P-43).


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## Sid327 (May 12, 2013)

I think,

if both the Merlin and Allison were tested without a supercharger there'd be very little in it; both being fine engines for the day.
It was just right place, right time for RR when they (Hooker) re-designed the supercharger system and applied it to the Merlin family.
The Allison by all accounts was a sweeter running engine(?)


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## GregP (May 12, 2013)

Some posted info is not consistent with my experience.

The early impellers were 8.25 inch, later they went to 9.5 inch, and in the G-6 and later engines they were 10.25 inch impellers. The impellers were NOT too small. The US government required Allison to use the turbosuperchagers (called turbochargers today) as the high-altitude boost system. As such, the normal supercharger impeller was supposed to handle things up to about 15,000 feet, which it did even in the 8.25 inch form.

When the War Materiel Board deleted the turbochargers from the P-39 engines to save them for the bombers (due to small US reserves of Tungsten), the high-altitude boost system required by the US government was lost and the P-39 had to make due with only the small supercharger that was supposed to have a separate high-altitude boost system. They left the turbos in the P-38 and, after the fuel and intake manifold issues were corrected, it performed just fine up to service ceiling except for a very poor cockpit heater, which left the pilots quite cold. It’s tough to get hot air all the way from the engine boom to the cockpit when the OAT is well below zero degrees! Electric heaters later cured that issue. If they had turbocharged the P-40, it would have performed MUCH differently. All they had to do was add a foot or two to the fuselage and it would have fit in just fine, according to several former engineers from Curtiss who have given talks at the Planes of Fame. 

I make no claims, I am just repeating what I heard here. Don't ask me for the plans ...

Allison asked the government at least twice if not three times if they should develop a 2-stage supercharger for the V-1710 and the answer was no. When you are a small engine company and your primary customer declines to pay for a development, it doesn’t get developed. Pure and simple. If the government had allowed the development to proceed, it could have been in service relatively quickly.

I do not claim the Allison-developed 2-stage integral supercharger would have been as good as those of Sir Stanley Hooker, but when you aren’t funded to at least try, you don’t get it at all. Some boost beats the crap out of NO boost. Also, it is true that if you don’t occasionally ask the impossible from your people, you damned for sure won’t get it. If the USAAF wanted a 2-stage supercharger, they should have funded it and simply didn't.

The angle between the accessory case and the intake is not acute and the interface is rather smooth. I should know since I worked helping overhaul them for Joe Yancey for almost 2 years and have been inside E, F, and G engines many times for both disassembly and buildup including the accessory case interface. The E and F are exactly the same except for the nose case. The E is for remote installations and connects to a driveshaft and the F has a propeller on the shaft. The G is a different animal with different parts and has a prop on the shaft, too. The displacement is the same. The crankshaft is the same 12-counterweight crank, but the G-series rods are much stronger, the intake is different, the nosecase is different, and the supercharger and accessory case are different with a bigger carburetor.

There is NOTHING inherently wrong in the Allison design and a 2-stage supercharger would have helped a lot. But someone had to pay for development if it was to be done, and the US government elected not to be that party. Allison couldn’t afford it on their own. So the government got what they asked for. Plain and simple.

The rotating main engine parts of all Allisons, including the 6-counterweight crankshafts, were all designed for 4,000 rpm but the nose case wasn’t. The approved rpm was 3,000 for almost all Allisons until the 12-counterweight crankshafts came out, at which time the approved rpm was raised to 3,200. The pilot had a “blip switch” and each blip would increase or decrease by 200 rpm. If you were in a dogfight and needed extra power, blip-blip and it was there. The crew chief might not like it, but you could DO it.

The approved MAP might have been 57 inches depending on model, but we have talked with a LOT of WWII pilots who said they sometimes used 3,400 rpm and 70 – 75 inches when they needed it. One was retired General Davey Allison (no relation) who demonstrated the P-40 to Claire Chenault. He said that he regularly used 70 inches in demos and never had an issue doing so. He was renowned for “getting the most from a P-40.” Of course, he didn’t have to work on his engines … and his crew chiefs might have hated his guts and probably did … I don’t know for sure.

Joe has engines out there with 1,300+ hours on them and are still running fine with normal maintenance after 15+ years. I don't know of any Merlins doing the same and don't really expect it either since that is a long time for a high-strung WWII V-12. 

I think the Merlin is a great engine. The Allison is somewhat maligned for no good reason. It did what it was designed and specified to do. The fact that the government didn't want to fund a 2-stage supercharger was a mistake. Allison did the next best thing and designed an auxiliary-stage supercharger that could be connected to the standard Allison (with a modified accessory case) to make a defacto 2-stage, although the aux stage was hydraulically driven and thus did not have a dogtooth altitude performance chart ... it was smooth. It was MUCH cheaper to design that than an entire new accessory case. The modified acdessory case had a hole drilled in it for the shaft to connect and a seal to be oil tight.

They SHOULD have been funded to develop a 2-satge integral unit ... but weren't. Ah well. Today nobody uses the Allison OR the Merlin high-altitude capabilities since that would be IFR. All warbird pilots want to play figher pilot, so they stay VFR on days of severe clear and dogfight when they get the chance at low altitudes where the difference between the Allison and the Merin is almost nothing. Both camps are usually happy with their engines today ... until they have to pay for an overhaul. Then the Allison guys are happier since the cost is about half of that for a Merlin.

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## wuzak (May 12, 2013)

GregP said:


> The early impellers were 8.25 inch, later they went to 9.5 inch, and in the G-6 and later engines they were 10.25 inch impellers. The impellers were NOT too small. The US government required Allison to use the turbosuperchagers (called turbochargers today) as the high-altitude boost system. As such, the normal supercharger impeller was supposed to handle things up to about 15,000 feet, which it did even in the 8.25 inch form.



In the turbocharged systems the turbo compensated for altitude, and that's all it did. And the integral supercharger was there to boost the intake charge above atmospheric (sea level) pressure. Which they did.

In engines without turbocharger the supercharger was to do both. It did this by being spun faster (different gearing). Unfortunately this meant that the engine couldn't take the boost the supercharger was capable of delivering at lower altitudes, so the intake had to be throttled to prevent overboosting.


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## R Pope (May 12, 2013)

The Allison is a much smoother running engine, all right, in the same way that a stock small block Chevy runs smoother than a blown Hemi in a dragster. The Merlin gets more power out of less displacement, so it is a bit rough around the edges, especially when starting up. 
One feature of the Allison is the relative simplicity of its construction. Less parts, and 'way less bolts! A Merlin has buckets full of little bolts all over the place, with multi-piece castings instead of one big one where possible. Also the Allison is lighter.


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## Aozora (May 12, 2013)

Greg, you might be interested in this which details the restoration to flight of the P-40N-1 42-104730, RAAF serial A29-448: The Whole Nine Yards. The Story of an Anzac P-40 by John King: Reed Books Pty P. Back - AbeBooks.co.uk











Some interesting comments on the V-1710 and the V-1710 v Merlin: 
















And performance figures:


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## drgondog (May 12, 2013)

Shortround6 said:


> P-51B was 7 in deeper top to bottom than a a P-51A, in part to fit the Merlin and the intercooler/larger radiator and larger duct.
> 
> .


Yes, but more for improving the aerodynamic transition from XP-51B (the P-51A airframe) cowling to wing - and hence the radiator/intercooler ducting boundary layer characteristics. Remember the 'hump' transition from lower engine cowl to wing on the XP-51A and the Mark X?


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## dobbie (May 12, 2013)

I really don't think the Allison was developed to its full potential. It produced more power down low than a lot of other liquid cooled engines and the A model Mustang down low was one of the fastest fighters on the deck in its time frame. That tells me they got a lot right with both the airframe and the engine. And as several people have pointed out, the Allison lasted a lot longer between overhauls, was lighter, and its modular construction paid off in its adaptability. Due to its construction, if the powers that be wanted a 2 speed 2 stage supercharger, I have to think that its development time would have been shorter.


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## Milosh (May 12, 2013)

Wasn't the Allison considered a 'sea level' engine? I read that someplace.


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## bob44 (May 12, 2013)

Here is an interesting report on the P51 with the Allison. One of the few times that puts the Allison above the Merlin.
E-GEH-16

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## tomo pauk (May 12, 2013)

Hello, dobbie,


> I really don't think the Allison was developed to its full potential. It produced more power down low than a lot of other liquid cooled engines and the A model Mustang down low was one of the fastest fighters on the deck in its time frame.


+1 on that.

We all know that from late 1943 on, the turboed V-1710 was making 1600 HP on 130 PN fuel, 3000 rpm. It was tested, eventually successfully, with 150 PN fuel (75 in Hg, 3000 rpm = 2000 HP); the lousy plumbing notwithstanding. Allison was also equipping their engines with water injection from late 1943 on; the engines were capable to make 3200 RPM on WER (5 min rating), later, with new crankshaft, 3200 rpm was available with military rating (15 min duration) - it would be interesting to see a turbo V-1710 with such improvements,


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## tomo pauk (May 12, 2013)

Milosh said:


> Wasn't the Allison considered a 'sea level' engine? I read that someplace.



'Sea level rating' engines were the engines with turbo. Ie. 'the engine was rated for 1200 HP from sea level up to 25000 ft of altitude'.
The 'altitude rated' engines were the ones with mechanical supercharger. Ie. 'the engine was rated for 1200 HP at 15000 ft of altitude'.

Allison V-1710 in P-38 was a sea level rated ones, the altitude rated engines were in P-39/40/51.


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## Shortround6 (May 12, 2013)

Milosh said:


> Wasn't the Allison considered a 'sea level' engine? I read that someplace.


 

"Sea Level" has to do with the _level_ of supercharging. It has nothing to do with the rest of the engine. 

Lets consider the Merlin III compared to the Merlin VIII, Pretty much the same engine, Coffman starter aside, EXCEPT the VIII used a 6.313 supercharger gear instead of the 8.588 gear of the III. 

What this did was lower the the FTL of 1030 hp at 16,250 ft and 6 1/4 lbs boost down to 1060 hp at 7500 ft at 4lbs boost. A serious problem for a plane that needed to fight at high altitude. 

What it did FOR the airplane was change the take-off rating from 880 hp at 3000 rpm and 6 1/4lb boost to to 1080 hp at 3000 rpm at 5 3/4lb boost. 

The Allison could be changed from sea level engine to an "altitude rated" engine by changing the supercharger drive gears. 

The problems with a single speed drive (and a single stage) are. 

1. *IF* your supercharger can only supply a pressure ratio of 2.8 to 1 and you need 44in of pressure to make rated power then you are limited to an altitude of about 17,000ft by simple mathematics. Engines are a bit more complicated. 

2. The faster you spin the supercharger (higher gear) the more power it takes ALL THE TIME and the more it heats the intake charge. The hotter the charge the less dense and the less power you make even at the same pressure. 
To keep from over boosting the engine at sea level you have to close the throttle down but the supercharger is still taking almost the same power to drive and heating the air a large amount. This is the 200hp difference in the two Merlin engines. 

SO you can either have power up high (if 15-17,000ft is high) or down low but not both. Or you can pick a compromise gear ratio with peak power at 9-12,000ft and get some of the take-off power back. 

This also explains two speed superchargers but they do little for power at 15,000ft and above for an engine that was already using a high gear ratio. 

Merlin X two speed engine used an 8.75 high gear and got 1010 hp at 17,750 ft using the same supercharger/inlet and carburetor as the Merlin III, 20 less hp 1500ft higher.


The "sea level" Allisons used a lower gear ratio than the 8.80 in the altitude rated engines. The First production P-38 engines used 6.44 gears and engines in later P-38s using 7.48 and 8.10 gears. 
Later altitude rated Allisons got 9.60 gears. 

Please remember that 1940/41 American 100 octane fuel was NOT the later 100/130 fuel and both boost and inlet temperatures had to be lower than later engines and also remember that the Allisons went through a number of modifications to beef up or strengthen various parts, there were four different crankshafts for example, all dimensionally interchangeable but able to handle different stress levels.

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## Hop (May 12, 2013)

> The Whole Nine Yards. The Story of an Anzac P-40 by John King: Reed Books Pty P. Back - AbeBooks.co.uk



In the last paragraph on page 141 the book claims the cost of the Packard V-1650 included a $6,000 royalty payment to Rolls Royce. This is wrong, there were no royalty payments made during the war. Rolls Royce were interested in charging royalties post-war, but Packard ended production.

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## GregP (May 12, 2013)

Thanks for the lead on the book, Aozora. I appreciate it.


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## fastmongrel (May 12, 2013)

Yes the Allison could have done everything the Merlin could with the advantages and disadvantages you will get with 2 different engines. Only problem it couldnt have done it in 1940 because no way is HM Government going to buy engines from the US pre war so you need to re engineer the Allison to British standards and build a factory just as Packard did for the Merlin. Go look at how long that took during wartime and consider that peacetime its probably going to take twice as long. So probably at the lastest in 1934 someone in the Air Ministry is going to have to persuade the Treasury to spend millions on a license for an experimental engine pretty much owned by another nations air force. 

Yeah like that is going to go smoothly and quickly.


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## Aozora (May 12, 2013)

Hop said:


> In the last paragraph on page 141 the book claims the cost of the Packard V-1650 included a $6,000 royalty payment to Rolls Royce. This is wrong, there were no royalty payments made during the war. Rolls Royce were interested in charging royalties post-war, but Packard ended production.


 
Yes, I was wondering about that statement as well; the source used is Vees For Victory!: The Story of the Allison V-1710 Aircraft Engine 1929-1948 (Schiffer Military History)



GregP said:


> Thanks for the lead on the book, Aozora. I appreciate it.



No sweat - if you want I can keep an eye open and find a copy because it doesn't seem to be an easy book to find on the net.


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## tomo pauk (May 12, 2013)

Hello, Fastmongrel,
To be fair, the introducing questions were:



> Was there any intrinsic design feature that precluded Allison engines from powering single engine fighters over Germany at 25000 feet, of was it all just a case of the American engine being hobbled by the thinking of the time - that high altitude fighters weren't required?



We all know that Allied fighters, flying over Germany at 25000 ft, were the thing of winter 1943/44 and later, not the thing of BoB vintage. I'd answer in this way: no, there was no any intrinsic feature that precluded Allison engines from powering single engine fighters over Germany at 25000 feet.
The second part of the question is covered by Shortrund6 in exemplary fashion.

The V-1710, being produced in UK on the other hand, does not make any sense, I agree with you. About the only US engine worth producing in the UK was the R-2800, IMO, and even that one would hardly influenced the ww2.


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## GregP (May 12, 2013)

Please keep an eye open for it. I will, too.


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## tomo pauk (May 12, 2013)

GregP said:


> Some posted info is not consistent with my experience.
> 
> The early impellers were 8.25 inch, later they went to 9.5 inch, and in the G-6 and later engines they were 10.25 inch impellers. The impellers were NOT too small. The US government required Allison to use the turbosuperchagers (called turbochargers today) as the high-altitude boost system. As such, the normal supercharger impeller was supposed to handle things up to about 15,000 feet, which it did even in the 8.25 inch form.



Neither the 8.25 in impeler (used in 2, yes, two, prototype GV-1710 engines) nor the 10.25 in impeller have nothing to do with ww2 warfare. Compared to Merlin's impeller (10.25 in, non-cropped), they were smaller, and the intake system have had far smaller inlet area, 'stealing' 2 in Hg of manifold pressure. That was noted by USAF brass Allison, where it was concluded that the rework of the inlet system of the single-stage V-1710 will demand 2-3 year work.
per 'Vee's for victory'



> When the War Materiel Board deleted the turbochargers from the P-39 engines to save them for the bombers (due to small US reserves of Tungsten), the high-altitude boost system required by the US government was lost and the P-39 had to make due with only the small supercharger that was supposed to have a separate high-altitude boost system. They left the turbos in the P-38 and, after the fuel and intake manifold issues were corrected, it performed just fine up to service ceiling except for a very poor cockpit heater, which left the pilots quite cold. It’s tough to get hot air all the way from the engine boom to the cockpit when the OAT is well below zero degrees! Electric heaters later cured that issue. If they had turbocharged the P-40, it would have performed MUCH differently. All they had to do was add a foot or two to the fuselage and it would have fit in just fine, according to several former engineers from Curtiss who have given talks at the Planes of Fame.
> 
> I make no claims, I am just repeating what I heard here. Don't ask me for the plans ...



I know there are some claims, but they don't add up. If War Materiel board wanted more turbos, they can save 2 on each unbuilt P-38, instead of 1 on each unbuilt P-39 (need 4 for B-17). The 'small US reserves of tungsten' would be the hanger talk, yes? How come the P-39 now ended up with small supercharger, since you deemed even the 8.25 in to be not to small (P-39 have had 9.50 inch one)? WHat would be the "a separate high-altitude boost system" for the P-39??? 
As for the P-38s heating system 'analysis', you cannot be really serious about that? The engine compartment was at about the same location as at another twin engined planes, and there was no talk about frozen pilots in Mosquitoes, Dinahs, Beufighters, Bf-110, Me-410, let alone at B-17/24, where their huge crew compartments received enough heating to keep 10-fold crew ready able. I'd say someone messed up the stuff in P-38 - Lockheed?
The tubo P-40 has it's own thread, hopefully this thread will be free from that hanger talk 'top of the pops'.




> Allison asked the government at least twice if not three times if they should develop a 2-stage supercharger for the V-1710 and the answer was no. When you are a small engine company and your primary customer declines to pay for a development, it doesn’t get developed. Pure and simple. If the government had allowed the development to proceed, it could have been in service relatively quickly.



+1 on this.



> I do not claim the Allison-developed 2-stage integral supercharger would have been as good as those of Sir Stanley Hooker, but when you aren’t funded to at least try, you don’t get it at all. Some boost beats the crap out of NO boost. Also, it is true that if you don’t occasionally ask the impossible from your people, you damned for sure won’t get it. If the USAAF wanted a 2-stage supercharger, they should have funded it and simply didn't.



They could went with auxiliary-stage earlier, provided it was funded.



> The angle between the accessory case and the intake is not acute and the interface is rather smooth. I should know since I worked helping overhaul them for Joe Yancey for almost 2 years and have been inside E, F, and G engines many times for both disassembly and buildup including the accessory case interface. The E and F are exactly the same except for the nose case. The E is for remote installations and connects to a driveshaft and the F has a propeller on the shaft. The G is a different animal with different parts and has a prop on the shaft, too. The displacement is the same. The crankshaft is the same 12-counterweight crank, but the G-series rods are much stronger, the intake is different, the nosecase is different, and the supercharger and accessory case are different with a bigger carburetor.



The G was not the ww2 engine, no matter how good it was to be (or not?), it's out of the thread's scope.



> There is NOTHING inherently wrong in the Allison design and a 2-stage supercharger would have helped a lot. But someone had to pay for development if it was to be done, and the US government elected not to be that party. Allison couldn’t afford it on their own. So the government got what they asked for. Plain and simple.



Agreed



> The rotating main engine parts of all Allisons, including the 6-counterweight crankshafts, were all designed for 4,000 rpm but the nose case wasn’t. The approved rpm was 3,000 for almost all Allisons until the 12-counterweight crankshafts came out, at which time the approved rpm was raised to 3,200. The pilot had a “blip switch” and each blip would increase or decrease by 200 rpm. If you were in a dogfight and needed extra power, blip-blip and it was there. The crew chief might not like it, but you could DO it.



Nice tid-bit. What planes were equipped with those?



> The approved MAP might have been 57 inches depending on model, but we have talked with a LOT of WWII pilots who said they sometimes used 3,400 rpm and 70 – 75 inches when they needed it. One was retired General Davey Allison (no relation) who demonstrated the P-40 to Claire Chenault. He said that he regularly used 70 inches in demos and never had an issue doing so. He was renowned for “getting the most from a P-40.” Of course, he didn’t have to work on his engines … and his crew chiefs might have hated his guts and probably did … I don’t know for sure.



I'm sure many pilots pushed their engines and got away with that. However, we don't hear much about the pilots that were pushing the engine and didn't got away with that (all rights reserved, SR6).


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## Milosh (May 12, 2013)

Shortround6 said:


> "Sea Level" has to do with the _level_ of supercharging. It has nothing to do with the rest of the engine.



Iirc what the definition of a 'sea level' engine was the Allison could only maintain its rated takeoff power at sea level with the power decreasing as altitude was gained. Thus a 'sea level' engine. An 'altitude engine' was an engine that could maintain its takeoff power to altitude.

Maybe the person who made the statement was talking out his rear end.


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## GregP (May 12, 2013)

Boy Tomo, you do ask a lot of questions.

The separate high-atitude boost system for the P-39 was a turbocharger that was ordered removed. It left few choices for Allison other than to change the supercharger gearing and try to make due with what was designed as the low-altitude boost system for the V-1710. That has been covered in earlier posts above.

If I had left out the 8.25 and 10.25 inch impeller, you would have mentioned it, too, wouldn't you? But I didn't claim any impeller got into combat, so what is your point? I said they were all used and they were. Allisons ran these three impellers during the design's evolution. During early design, it was assumed the turbo would be available, When that proved not to be the case, they had to take as expedient action as they could to compensate for a major engine change that was unexpected. I doubt anybody who had developed their design WITH the turbo could have done much better in as short a time when the turbo was suddenly and unexpectedly taken away. On the other hand, Rolls-Royce DID have Sir Stanley Hooker, though even HE might have a hard time if a turbo was suddenly removed from one of his designs. It might require serious redesign. Don't know, it didn't happen.

The title of the thread doesn't specify WWII, it asks whether the Allison could have done what the Merlin did. Both engines were in use before, during, and after WWII. The Planes of Fame still uses both today. The G-series engines ran in 1942 but, yes, the P-82 was a post-war product, much as the de Havilland Hornet was, too, even though it used engines that were developed and ran in WWII, too. If you want to confine it to WWII, then the P-82 is surely not included.

The blip switch was the swtich used to set the rpm of the constant-speed propeller. I know the P-40E and N have it but would only be guessing about the rpm control of the rest since I have never asked about it when I am in one of the cockpits. I was making the assumption that rpm control was fairly standardized, but that might be wrong. All have SOME type of rpm control that is easily used if more rpm is desired.

Last point, very much agree. If someone blew up their Allison or Merlin (or radial, or DB, Jumo, or Homare, etc.), they'd likely not tell anbody if they managed to get back home before the war ended. Likey as not it would get reported as an "engine faiure." Honesty has never been one of humankind's top 10 traits, has it?


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## Aozora (May 12, 2013)

Re manual prop control: is this the control being referred to? Kittyhawk I Pilot's Notes:










cf the fully automatic system on the V-1710-99 (later P-40Ns):


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## GregP (May 12, 2013)

That's the one. The guys flying at Reno in the stock Bronze class use it all the time, especially if they're second to last and about to be passed. 


One of our friends was flying a stock P-40E in Bronze acouple of years ago and a Corsair cranked up the power and decided to not come in last. He started creeping up on the P-40 and the pilot gave a couple of blips on the manual rom switch as just pulled away from the Corsair. You won't see THAT in the books or in the numbers, but it happened at Reno.


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## Shortround6 (May 12, 2013)

Milosh said:


> Iirc what the definition of a 'sea level' engine was the Allison could only maintain its rated takeoff power at sea level with the power decreasing as altitude was gained. Thus a 'sea level' engine. An 'altitude engine' was an engine that could maintain its takeoff power to altitude.
> 
> Maybe the person who made the statement was talking out his rear end.



It may depend on WHEN he talking about. The Engine was _originally_ designed for 750hp/2400rpm?at sea level with NO supercharger, or at least that is the spec for the the second version of the first engine. There was a lot of rebuilding of the first few engines so I may be wrong about that. Fuel was 80 octane.
The Army changed the requirement to 1000hp for take-off at 2660-2650rpm at sea level on 92 octane fuel. This was in 1932 I believe and this level of power required supercharging from a 1710 cu in engine. The Army was planning on altitude performance to be supplied by the additional turbo unit. 
As the years wore on and compression ratios changed, rpm limits changed, fuel changed and the Army not only failed to buy engines in more that batches of 1 or 2 but was falling behind in payments for work done Allison may have been looking to broaden it's possible market. GM was now a part owner and was sinking money into the project to keep it going. 

In 8 years from 1930-38 the fuel had changed from 80 to 100 octane, materials had changed, the engine had gained weight and rpm had increased due to better understanding of both vibration (and how to damp it) and materials. 

What the engine was capable of had changed drastically (so had other engines capability, check out a 1930 Wright Cyclone compared to a 1938 version) so does the "sea level" engine still apply? 

Allison was offering the "altitude" rated engine in hopes of getting _some_ sales as talks or requests between Allison and some airframe makers started in 1937 over the possibility of an altitude rated engine.

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## GregP (May 13, 2013)

Whatever theyt're "rated," most engines were tested in an altitude chamber or at height using speed as the variable and the power available at altitude is pretty well known.


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## Jugman (May 13, 2013)

Hop said:


> In the last paragraph on page 141 the book claims the cost of the Packard V-1650 included a $6,000 royalty payment to Rolls Royce. This is wrong, there were no royalty payments made during the war. Rolls Royce were interested in charging royalties post-war, but Packard ended production.




According to author Robert J. Neal There were royalty payments in the range of $3000-$4000. I remember reading somewhere that it was the British government that actually payed the royalties and not Packard. It's true that Rolls-Royce _was not_ allowed to charge Ford UK royalties.


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## GregP (May 13, 2013)

Until after the war, when it kicked in ... and we quit making Merlins. Which is probably the way it was supposed to be, absent of war.

During war, necessities are expedited, after it is over, civil laws kick in and a return to normalcy is pretty standard.

Just because the British needed Merlins doesn't mean they would abandon the patents after the war, not should they have done so unless abandoning the engine themselves, in which case it would not have mattered since the inventors would be discarding the invention.


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## tomo pauk (May 13, 2013)

GregP said:


> Boy Tomo, you do ask a lot of questions.




I also love to read answers that can tech me a thing or two. I dislike when my questions remain unanswered, however. But I guess all of us do.



> The separate high-atitude boost system for the P-39 was a turbocharger that was ordered removed. It left few choices for Allison other than to change the supercharger gearing and try to make due with what was designed as the low-altitude boost system for the V-1710. That has been covered in earlier posts above.



Okay; after re-reading your post again, it all fits in.



> If I had left out the 8.25 and 10.25 inch impeller, you would have mentioned it, too, wouldn't you?



Sorry if I made the impression of being a person with bad intentions towards you here, that was not what I'm here for. 



> But I didn't claim any impeller got into combat, so what is your point? I said they were all used and they were. Allisons ran these three impellers during the design's evolution. During early design, it was assumed the turbo would be available, When that proved not to be the case, they had to take as expedient action as they could to compensate for a major engine change that was unexpected. I doubt anybody who had developed their design WITH the turbo could have done much better in as short a time when the turbo was suddenly and unexpectedly taken away. On the other hand, Rolls-Royce DID have Sir Stanley Hooker, though even HE might have a hard time if a turbo was suddenly removed from one of his designs. It might require serious redesign. Don't know, it didn't happen.



Easy to agree what you've said here; the V-1710 have had a long and rocky road in front to travel.



> The title of the thread doesn't specify WWII, it asks whether the Allison could have done what the Merlin did. Both engines were in use before, during, and after WWII.



But the opening post specifies _"Was there any intrinsic design feature that precluded Allison engines from powering single engine fighters over Germany at 25000 feet"_ - and in any book that means the time period of mid/late 1943 until the VE day. 
If you bother to read my post, number 36 in this thread, you will know that my opinion is that V-1710 was able to do that job.



> The Planes of Fame still uses both today. The G-series engines ran in 1942 but, yes, the P-82 was a post-war product, much as the de Havilland Hornet was, too, even though it used engines that were developed and ran in WWII, too. If you want to confine it to WWII, then the P-82 is surely not included.



Of course the P-82 and Hornet are not included.



> The blip switch was the swtich used to set the rpm of the constant-speed propeller. I know the P-40E and N have it but would only be guessing about the rpm control of the rest since I have never asked about it when I am in one of the cockpits. I was making the assumption that rpm control was fairly standardized, but that might be wrong. All have SOME type of rpm control that is easily used if more rpm is desired.



Doh. 
In other words, the story about as many RPM (above the rated limit, 3000 rpm for most/all ww2 V-1710) as pilot wants is just that, a story.



> Last point, very much agree. If someone blew up their Allison or Merlin (or radial, or DB, Jumo, or Homare, etc.), they'd likely not tell anbody if they managed to get back home before the war ended. Likey as not it would get reported as an "engine faiure." Honesty has never been one of humankind's top 10 traits, has it?



It would be indeed fine if the pilot returns, after his engine blows up in mid-air, esp. over enemy territory or some big chunk of sea.


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## Balljoint (May 13, 2013)

A big picture factor in this discussion is the siren song of the turbo. It was intrinsically the better technology. However, the key to realizing compact, efficient turbochargers is the temperature that the turbine runs at. High-temperature alloys/ceramics weren’t available during the early forties so the tungsten alloy turbines used nozzles that produced relatively low temperatures and efficiencies. These worked but were far from optimum.
Jet engines, being turbines, have the same requirement. When the metallurgy ramped up the meet the need it was too late. Modern aero turbo chargers would outperform superchargers nicely. However, in aviation, the pure turbine engine has replaced the internal combustion engine with a hot section.


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## nincomp (May 13, 2013)

tomo pauk said:


> It would be indeed fine if the pilot returns, after his engine blows up in mid-air, esp. over enemy territory or some big chunk of sea.



You are technically correct, but I think that GregP the phrase "blow up" as it is commonly used in aircraft and automotive racing in the US. When an engine is damaged during a race, we often use the phrase "blew an engine." Often an engine "blows up" during an attempt to get too much power from it. Sometimes an engine can continue running at a lower output for a while before it seizes completely.

Your English is excellent. It is next to impossible to know all of slang terms used by the various English-speaking countries. I regularly get confused when communicating with people from other English speaking countries.

Jim


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## GregP (May 13, 2013)

Hi Tomo, 

No the rpm thing is not a story. The engines can eaily run to 3,400 rpm and more, even the 6-counterweight variety. There is some limit for the prop and nosecase, and I wouldn't want to try 3,600 rpm myself unless I had a Messerschmitt on my tail and really needed to try it. Then it wouldn't matter whether you die from German fire or go down from losing a prop blade, you're probably going down one way or the other and might aas well try it.

The Allison itself doesn't have any trouble going even to 4,500 rpm when mounted on a tractor in Europe doing tractor pulls. Joe Yancey had a customer in Europe who had been running his engines on a tractor for more than 6 years without a failure and he runs them at 4,500 rpm for a pull. Of course he isn't running a prop and isn't running for long duration either. One customer ran the same tractor in both 2 and 3 engine classes and simply removed one engine for a 2-engine pull.

Most WWII-era military fighters had an automatic rpm control and a manual backup (the blip switch). The exact control placement differs among cockpits. I know where the main prop controls are in the P-38 (right next to the throttles), but am unsure about the manual rpm control. Since I'll never fly one, it didn't seem all that important at the time. They all connect to the same spot on the Allison itself, and that would be the prop governor located on the nosecase. Most Allison installations used a Curtiss Electric prop, and that governor is quite different from a hydraulic governor used to control hydromatic props.


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## zjtins (May 15, 2013)

The Allison had slight more displacement at the same compression ratio and weighed 300 lbs less. So given the right compression scheme yes it could have been better than the Merlin.


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## tomo pauk (May 15, 2013)

Single stage V-1710-81: 1352 lbs dry weight; V-1610-1: 1520 lbs (two speed supercharger, maybe 10% more power at most of the altitudes)
Two stage V-1710-101: 1540 lbs (ADI system adds 50 lbs); V-1650-3/7: 1690 lbs (+ inter-cooler weight - 200 lbs?; more power at high altitudes).

We can note that RR Merlins were available earlier than Packard Merlins, that would be their crucial advantage.


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## wuzak (May 15, 2013)

tomo pauk said:


> Single stage V-1710-81: 1352 lbs dry weight; V-1610-1: 1520 lbs (two speed supercharger, maybe 10% more power at most of the altitudes)



I guess the equivalent of the V-1710-81 would be the single stage, single speed Merlin 45. 
Merlin 45 - 1385lb, 1230hp @ 18,000ft.
Merlin 45M - 1585hp @ 3000ft.




tomo pauk said:


> Two stage V-1710-101: 1540 lbs (ADI system adds 50 lbs); V-1650-3/7: 1690 lbs (+ inter-cooler weight - 200 lbs?; more power at high altitudes).



I think the typical two stage V-1710 was heavier.

In any case, 50lbs can't give much ADi duration?

The 200lbs you are adding for the V-1650-3/7 is for the radiator and fluid?

Lumsden has 1640lb for Merlin 61/V-1650-3, 1690lb for V-1650-3/Merlin 63, 1645lb for the Merlin 63 and 1645lb for the V-1650-7.


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## tomo pauk (May 15, 2013)

wuzak said:


> I guess the equivalent of the V-1710-81 would be the single stage, single speed Merlin 45.
> Merlin 45 - 1385lb, 1230hp @ 18,000ft.
> Merlin 45M - 1585hp @ 3000ft.



Yep, a better comparison is with Merlin 45, and that one makes more power on about same weight.




> I think the typical two stage V-1710 was heavier.



The -121 was the one in XP-40Q-2, data is from here. 



> In any case, 50lbs can't give much ADi duration?



50 lbs was equal to 15 min of duration of ADI in P-63.



> The 200lbs you are adding for the V-1650-3/7 is for the radiator and fluid?



Yes.



> Lumsden has 1640lb for Merlin 61/V-1650-3, 1690lb for V-1650-3/Merlin 63, 1645lb for the Merlin 63 and 1645lb for the V-1650-7.



My data is from the document quoted above. Seems Lumsden gives 2 different weights for V-1650-3?


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## zjtins (May 15, 2013)

I was using 1,340 lb Allison dry weight vs 1,715 lb dry weight Merlin. Not sure of the version. From Air and Space museum website.


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## wuzak (May 15, 2013)

tomo pauk said:


> My data is from the document quoted above. Seems Lumsden gives 2 different weights for V-1650-3?



Yes, he does. One is listed under Merlin 61 - so that would be the early models. The other was listed under Packard V-1650-3 and as equivalent to the Merlin 63. One change that was possibly made was the supercharger drive system - most 2 stage Packards used the Wright epicyclic gears.


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## CobberKane (May 16, 2013)

My God, I knew I was asking for it when I posted this thread. Just to re-focus for myself and anyone else who doesn't know a turbocharger from a rice cooker, it would seem that there was nothing in particular about the basic Allison V-12 that precluded it being developed to do what the RR Merlin did, so long as you had;

A) the incentive and resources to do so, and
B) Sir Stanley Hooker

Fair enough?

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## Shortround6 (May 16, 2013)

Pretty much, There was nothing wrong with the Allison's block, crank, rods, pistons, heads, valves (in fact the Allison head/valve design may be a bit better), lubrication or build quality. 

Pretty much the only difference in "real" performance was the supercharger set ups fitted. 

AND BOTH engines progressed during the the war. A 1945 Merlin had bits and pieces that were not in a 1940 Merlin or were beefed up/changed and a 1945 Allison had quite a few changes from a 1940 Allison. For the most part you could swap the new pieces in and out or back and forth but you could NOT take a 1940 engine and run 100/150 fuel in it and pull the boost levels that a 1944/45 engine would tolerate. At least not for very long


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## zjtins (May 16, 2013)

> AND BOTH engines progressed during the the war. A 1945 Merlin had bits and pieces that were not in a 1940 Merlin or were beefed up/changed and a 1945 Allison had quite a few changes from a 1940 Allison. For the most part you could swap the new pieces in and out or back and forth but you could NOT take a 1940 engine and run 100/150 fuel in it and pull the boost levels that a 1944/45 engine would tolerate. At least not for very long


Same for the British built Merlin.


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## XBe02Drvr (Apr 2, 2020)

GregP said:


> Most Allison installations used a Curtiss Electric prop, and that governor is quite different from a hydraulic governor used to control hydromatic props.


Wandering through the mists of history, I came upon the above statement.
Having taken apart and put together hydraulic governors in school, and been told: "Forget electrics, you'll never see one! (If you're lucky)", I'm curious: what is the difference? It seems logical that if you replaced the flow valves at the base of the flyweights follower shaft with electrical contacts, you'd have an electrical prop governernor. Other than that, a similar device. What am I missing, Greg? Anybody want to jump in here?
Cheers,
Wes


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## Koopernic (Apr 2, 2020)

If Britain faced a shortage of Merlins it could theoretically have powered the Lancaster, Wellington, Halifax & Beaufighter with the Allison. It was a while before the two speed superchargers were used on the Merlins I believe. 

The turbo-charged Allision probably could have been fitted to these British bombers. A Turbo charged Allison on a Lancaster might give it quite a good altitude performance, perhaps as good as the Liberator.

USAAF policy seems to have been to use simple single speed single stage non intercooled superchargers, some were two speed superchargers without intercooling, for low flying aircraft and turbo-superchargers for high altitude. This infamously left the P39, P40 and P51A with poor altitude performance while the P-38 went through years of extended debugging and the P-47 was still in development.

The US Navy had quite a different policy, it used multispeed multi stage superchargers with independent stage drives and intercooling. Eventually these navy R2800 engines did find themselves on some USAAF aircraft.

Unfortunately the USN never used the Allison and aircraft (only air ships), had it have chosen too it might have provided the funds and impetus to develop a mechanical superchargers for the Allison.


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## wuzak (Apr 2, 2020)

Koopernic said:


> If Britain faced a shortage of Merlins it could theoretically have powered the Lancaster, Wellington, Halifax & Beaufighter with the Allison. It was a while before the two speed superchargers were used on the Merlins I believe.



All those aircraft you listed used two speed Merlins.

The Lancaster and Beaufighter had Merlin XXs (the latter was because of possible supply problems with the Hercules).

The Halifax started life with the Merlin X, before later getting the Merlin XX and then the Hercules.

The Wellington Mk.II had the Merlin X. Most had the Hercules, however.

The Whitley Mk IV had a single speed Merlin until late production models, which had the X. The Whitley Mk V had the Merlin X, first flying in late 1938.




Koopernic said:


> The turbo-charged Allison probably could have been fitted to these British bombers. A Turbo charged Allison on a Lancaster might give it quite a good altitude performance, perhaps as good as the Liberator.



Yes, a turbocharged V-1710 would have worked in the Lancaster, probably not worth it on the others. 

However, there would have been a lot of redesign necessary to fit the turbocharger, intercooler, etc.

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## wuzak (Apr 2, 2020)

Koopernic said:


> Unfortunately the USN never used the Allison and aircraft (only air ships), had it have chosen too it might have provided the funds and impetus to develop a mechanical superchargers for the Allison.



The Bell XFL-1 Airabonita was a V-1710 powered aircraft proposed for the USN, but not adopted.


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## Shortround6 (Apr 2, 2020)

Two speed Merlins (the Merlin X) were shown at the 1938 Paris air show/exhibition. And were just starting squadron service in Whitleys out the outbreak of the war. 
The Merlin XX with two speed supercharger was in production in the late summer of 1940. 

Any British bomber trying to use Allisons in late 1939 or the first part of 1940 would have been in big trouble. All Allisons manufactured for the US up until that time had to be derated in service (max rpm 2770) until they could be sent back to the factory and rebuilt. 

In 1939/40 the Allison used in the P-40 was the highest altitude Allison they could build. Itis a myth to claim that a two speed supercharger drive would have improved anything except take-off power. 

US "Policy" in 1939/early 40 was to get planes that would actually work, Which the turbo equipped prototypes often didn't. It also took P & W a while to fully sort out the 2 stage supercharger used in the Wildcat. Early planes suffered from breakdowns in airflow and compressor stall which was manifested in rumblings in the supercharger ducts. 
Having planes with a low service ceiling beat having no planes at all.


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## wuzak (Apr 2, 2020)

Shortround6 said:


> In 1939/40 the Allison used in the P-40 was the highest altitude Allison they could build. Itis a myth to claim that a two speed supercharger drive would have improved anything except take-off power.



Of course if your engine already is rated to a (relatively) high altitude, the second gear helps low down power, which had been sacrificed for the altitude performance.

And the improvement in take-off power is why the UK bombers got the X and the Spitfire and Hurricane didn't (the Hurricane dd get the XX at the end of 1940).

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## Shortround6 (Apr 2, 2020)

You are quite right. this story about the US aircraft at the beginning of the war being "low altitude" gets wide circulation but has little basis in fact. 

They may have been low altitude due to being heavy for the available engine power, but the Allison in 1940 was not that far behind the Merlin III and was ahead of the DB601 (at least some models).

The reason the US radials got two speed superchargers was to help take-off performance of large transports and bombers.


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## Koopernic (Apr 5, 2020)

Shortround6 said:


> SNIP
> 
> In 1939/40 the Allison used in the P-40 was the highest altitude Allison they could build. Itis a myth to claim that a two speed supercharger drive would have improved anything except take-off power.
> 
> ...



A two speed single stage supercharger on the V-1710 would have done much more than increase take-off power. It would have provided 100hp more power all the way to 9200ft if the Merlin 27 (two speed) used in the Hurricane IV versus the Merlin 46 (single speed) Used in the Spitfire Vc. The lower first stage speed is more efficient leading to loss in parasitic shaft power and less preheating of the mixture and therefore increased boost. Speeding up the second gear may not yield much but it may have been compromised to yield reasonable low altitude performance. What two speeds would allow is the introduction of a larger impellor, no more than 10% greater diameter) that was more efficient a high altitude. I wouldn't be much of a gain but it would be something.

And who knows where this might have lead. Junkers improved the Jumo 211 not only with a two speed supercharger but intercooling which gave over 1500hp at high altitude on 87 octane.

The problem with turbosuperchargers in the US was that they were so bulky and tightly packe a reliable installation couldn't be made on single engined aircraft. There are only a few solutions
1 Integrate them only in twins using the nacelle space
2 Make a special airframe eg the P47
3 Integral turbo charger where the manufacturer builds the turbo, intercooler into a unitary body. This was the route the Germans went after having learned the lesson of the Fw 190 Kangaroo but the effort was abandoned as not worth while though they made integral turbos for the BMW801 (retaining two speed supercharger on top of the turbo)


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## Shortround6 (Apr 5, 2020)

Koopernic said:


> A two speed single stage supercharger on the V-1710 would have done much more than increase take-off power. It would have provided 100hp more power all the way to 9200ft if the Merlin 27 (two speed) used in the Hurricane IV versus the Merlin 46 (single speed) Used in the Spitfire Vc. The lower first stage speed is more efficient leading to loss in parasitic shaft power and less preheating of the mixture and therefore increased boost. Speeding up the second gear may not yield much but it may have been compromised to yield reasonable low altitude performance.



While what you say is true it also condenses the time frame by several years. 
In 1939-40 using the existing Allison supercharger going to a two speed drive is not going to gain much at all except in in take-off/low altitude power, Very low altitude power. 

The Hooker modified supercharger didn't exist at this time and the supercharger on the Merlin 46 was still a considerable period of time away. 

The Long nose Allison was rated at 1040hp at 12,800ft with backfire screens. some sources give bit higher altitude, like 14,300ft. The engine was also rated at 1040hp for take-off. Unlike the Merlin III. 
However the long nose Allison had a few problems which probably prevented trying to drive a higher supercharger gear for better high altitude performance (the famous 9.60 gear).

Please note the C-15 engine (V-1710-33) used in the early P-40s had the following changes from earlier C series engines.
Improved supercharger thrust bearing and change from 6.23 gears to 8.77 gears.
Heavier 15 blade impeller of improved design instead of 12 blade impeller.
Rotating steel inlet guide vanes. 
Bendix 3 barrel carburetor instead of a two barrel carburetor
Larger supercharge cover to accommodate the bigger carburetor.
Modified supercharger diffuser. 

There were other changes but those are the ones done to the supercharger to improve altitude performance. 

US had an advantage in that the engine was designed to use 100/100 fuel instead of 87 octane fuel.

However the early C-15s had structural problems and the first 228 built had to be recalled and fitted with new crankshafts, crankcase and a few other parts to make rated power. Until that was done they were de-rated to 2770rpm and 950hp for take-off and 950hp at 8,000ft. 

Ability of an unmodified engine to turn 9.60 gears for improved altitude performance is subject to question even if such gear had been available and even if such gear had stood up to the load (which they did not in the Nov-Dec 1941) D and E series engines. 

Grafting the Merlin 46 supercharger and most especially the Merlin 27 drive onto the back of an Allison would be a major undertaking. perhaps it is one that _should_ have been done. but it would have been at a different time than the C-15 productin was going on. and perhaps the people in charge did not want to approve the drop in production that would have meant. Allison built 502 engines in July of 1941 and over 1100 in Dec of 1941 and stayed between 1039 and 1379 per month for all of 1942. When in 1942 would have been a good time to loose several hundred engines when the change was made?


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## tomo pauk (Apr 5, 2020)

Koopernic said:


> A two speed single stage supercharger on the V-1710 would have done much more than increase take-off power. It would have provided 100hp more power all the way to 9200ft if the Merlin 27 (two speed) used in the Hurricane IV versus the Merlin 46 (single speed) Used in the Spitfire Vc. The lower first stage speed is more efficient leading to loss in parasitic shaft power and less preheating of the mixture and therefore increased boost. Speeding up the second gear may not yield much but it may have been compromised to yield reasonable low altitude performance. What two speeds would allow is the introduction of a larger impellor, no more than 10% greater diameter) that was more efficient a high altitude. I wouldn't be much of a gain but it would be something.



The V-1710 with a bigger impeller would've been a net gain, even if it featured just 1-speed drive for the impeller.



> And who knows where this might have lead. Junkers improved the Jumo 211 not only with a two speed supercharger but intercooling which gave over 1500hp at high altitude on 87 octane.



Junkers didn't improved the 211 with a 2-speed S/C drive, it was already there. They did improve the 210 with 2-speed S/C drive.
Jumo 211 never did more than 1300 HP at altitue (talk 5 km and above), the 1500 HP power was achieved at low level. The turbocharged 211Q did it, but it it was not used on a service aircraft.



> The problem with turbosuperchargers in the US was that they were so bulky and tightly packe a reliable installation couldn't be made on single engined aircraft. There are only a few solutions
> 1 Integrate them only in twins using the nacelle space
> 2 Make a special airframe eg the P47
> 3 Integral turbo charger where the manufacturer builds the turbo, intercooler into a unitary body. This was the route the Germans went after having learned the lesson of the Fw 190 Kangaroo but the effort was abandoned as not worth while though they made integral turbos for the BMW801 (retaining two speed supercharger on top of the turbo)



The P-43 was certainly a 1-engined aircraft, not some 'special airframe' so the turbocharger can be used.
Germans made a mistake by not pressing the turboed BMW 801 in service on Fw 190 (not that making such a Fw 190 would've changed the outcome of the war by a single jota). The Kangaroo installation was appalling indeed.


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## drgondog (Apr 5, 2020)

tomo pauk said:


> Great post, indeed.
> 
> There was no major hurdle to install the two stage V-1710 (the 'normal' drive equivalent of the E-11 installed in the P-63A) in the P-51 airframe and send it in the ETO in 1944. The altitude performance would not be on par with the Merlin Mustang, esp. vs. the early models with the high altitude V-1650-3, but it should be enough for a decent performance advantage vs. the LW opposition.
> Another approach could've been the single engined fighter with turbo V-1710, something along the lines of the XP-60A (3 view). The plane based around that power-plant was feasible as early as P-38.



Actually Tomo - the auxiliary second stage was an absolute no-go from NA-73 through NA-122. The added required movement of the engine in front of the firewall made a complete re-design including moving the wing forward, larger empenage - based on AAF and GM request to 'look and see', layouts were made in response. It was only after much whining and some sympathy from AAF was the Allison tried in the P-51J.

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## Shortround6 (Apr 5, 2020)

People *may* be _ignoring_ the materials limitations of the time. 







Turbo compound Allison at the end of the war. Extra power from the turbine, over and above that needed to drive the auxiliary supercharger was routed through the driveshaft into rear of the engine to the crankshaft. 

Granted this engine was operating at much higher pressures and temperatures than early war engines did but it was found that they needed to inject water/alcohol into the exhaust system to keep the inlet temperature to the turbine within limits or risk turbine blade failure. 

I have never seen it it written out but there may have been a very good reason that US turbos were mounted a number of feet away from the engine and usually with a number of feet of the exhaust duct exposed to the open air before it reached the turbine. Only the P-47 enclosed the turbine and it was quite a number of feet from the engine.

Trying to closely package the turbine to the engine just because you had room(?) might not have been a good idea? 
Again I can't prove it but please remember there was quite a bit of work going with different turbos and uprated materials and rpm limits as the war went on. 
Saying they should have done XXX in 1941 because they could do it in 1944/45 may not be correct.

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## tomo pauk (Apr 5, 2020)

Shortround6 said:


> ...I have never seen it it written out but there may have been a very good reason that US turbos were mounted a number of feet away from the engine and usually with a number of feet of the exhaust duct exposed to the open air before it reached the turbine. Only the P-47 enclosed the turbine and it was quite a number of feet from the engine.
> 
> Trying to closely package the turbine to the engine just because you had room(?) might not have been a good idea?
> Again I can't prove it but please remember there was quite a bit of work going with different turbos and uprated materials and rpm limits as the war went on.
> Saying they should have done XXX in 1941 because they could do it in 1944/45 may not be correct.



The last sentence is right on the money - the internally-cooled turbine blades were not used on turbochargers (in service, not what people had on the test benches) before 1944. Germans started some time in mid 1944 on BMWs powering the Ju 388, the Americans used it on the turbo for the Curtiss SC Seahawk (about 1000 turbochargers manufactured by Wright).

'Early' American approach worked on the technology of the day.


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## GregP (Apr 5, 2020)

When the US sent out the actual requirement that resulted in the Allison V-1710, it specified a single-stage supercharged engine and, if a higher altitude capability was desired, the aircraft could use the newly USAAC-developed turbo-supercharger, or turbocharger as we call it today. The USAAC overestimated the state of development of its own turbocharger. General Electric was the sole source of American turbochargers during this period and for most of the US involvement in WWII.

The Allison Engine Company built engines to order, and the government ordered what they wanted. Over 60% of the post-1941 pursuit aircraft were powered by the Allison V-1710 that were almost all single-stage supercharged engines either with or largely without the turbocharger. The early V-1710’s were about 1,000 HP and the late P-38L was 1,600 Hp, while the final V-1710-143/145 was rated at 2,300 HP maximum.

Improvements in manufacturing brought the cost down from $25,000 to $8,000 and allowed the installed lifetime to be increased from an initial 300 hours to as much as 1,000 hours for the less-stressed powerplants. Weight increases were minimal with the result that all models were able to produce more than 1 pound per horsepower at takeoff rating.
Comparisons with the Merlin are inevitable. What CAN be said is the Allison made more power with less boost, had a longer time between overhauls, and did so with a parts count that was nearly half that of the Merlin (around 7,000 Allison parts versus 11,500+ Merlin parts). There was a high degree of commonality of parts throughout the series and individual parts were produced to high degree of standardization and reliability. The Allison was not particularly vulnerable to ground fire though the liquid cooling systems used had various degrees of same.

Saying the above does not detract from the Merlin engine at all. Rolls Royce developed a very good supercharger thanks to Sir Stanley Hooker. It virtually made the difference in that engine family, though there were other improvements as well.

The original Bell P-39 prototype had a turbosupercharger that was specified by Ben Kelsey and Gordon Saville. Numerous changes were made while Kelsey was busy with P-38 work, and the turbocharger was deleted, making the P-39 a low-altitude fighter that was not suited to Europe’s higher altitude requirements. The P-39 was rejected by the British but was used by the U.S.A. in the Mediterranean and Pacific Theaters, and particularly by the Soviet Union in large numbers. In the P-39, Soviet fighter pilots scored the highest number of individual kills made in ANY US or British fighter type, primarily because the Soviet war was a tactical, short-range, low-altitude war.

The Allison V-1710 initially had some issues in Europe. Some of the issues were: 1) Poor intake design (Allison), 2) poor regulation of the turbocharger temperature (GE), different fuel formulation from that used for development (not sure it was anyone's fault). The P-38 also had a very poor cockpit heater, which was a major problem in Europe's higher-altitude environment. Last, one of the biggest issues was poor or almost complete lack of pilot training on good flying practices when entering combat areas. The intake design, fuel issues, cockpit heater, and pilot training were “fixed” within a year, but the temperature regulation of the turbochargers was never really fixed by General Electric.

Today, Allison V-1710 engines are smooth and reliable in warbird use when built with "late" 100-series internal parts regardless of the dataplate "dash" number. Merlins are likewise reliable. Today, there is no high-altitude requirement for either engine and both are used with little thought of engine failure unless the use is for racing.

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## wuzak (Apr 5, 2020)

GregP said:


> When the US sent out the actual requirement that resulted in the Allison V-1710, it specified a single-stage supercharged engine and, if a higher altitude capability was desired, the aircraft could use the newly USAAC-developed turbo-supercharger, or turbocharger as we call it today.



Actually the turbocharger was developed by General Electric. This was initiated by NACA and then funded by the USAAC.

Not many aircraft engines had a supercharger with more than one stage when the V-1710 program was initiated in 1929. Some didn't even have a supercharger at all.




GregP said:


> The USAAC overestimated the state of development of its own turbocharger. General Electric was the sole source of American turbochargers during this period and for most of the US involvement in WWII.



GE was the sole source of production turbochargers for the USAAC/F for the duration of the war. Other turbochargers were trialled, but never went into production.

GE was also the source of most of the aero industry's supercharger designs for most of the 1930s. This included Allison.




GregP said:


> The Allison Engine Company built engines to order, and the government ordered what they wanted.



All engine manufacturers built engines to order. No pint building 1,000 engines that nobody wants of can use.




GregP said:


> Improvements in manufacturing brought the cost down from $25,000 to $8,000 and allowed the installed lifetime to be increased from an initial 300 hours to as much as 1,000 hours for the less-stressed powerplants. Weight increases were minimal with the result that all models were able to produce more than 1 pound per horsepower at takeoff rating.



The cost fell with the increase in production. Not really related to any engineering improvements.




GregP said:


> Comparisons with the Merlin are inevitable. What CAN be said is the Allison made more power with less boost, had a longer time between overhauls, and did so with a parts count that was nearly half that of the Merlin (around 7,000 Allison parts versus 11,500+ Merlin parts).



Oh no, not the parts count again! Considering that most of the difference was composed of extra fasteners. And is the comparison like-for-like? That is, are we comparing single stage, single speed version of the Merlin with the V-1710, which, as you noted, was almost always single stage, single speed.

Of course the fact that the Merlin was typically rated at higher altitudes had no bearing on this. If it is true at all.



GregP said:


> The early V-1710’s were about 1,000 HP and the late P-38L was 1,600 Hp, while the final V-1710-143/145 was rated at 2,300 HP maximum.



That 2,300hp version was at 100inHg manifold pressure. Meanwhile the Packard V-1650-9 was not far behind on a mere 90inHg manifold pressure.




GregP said:


> here was a high degree of commonality of parts throughout the series and individual parts were produced to high degree of standardization and reliability.



And Merlins were hand crafted by fitters using files and feeler gauges and drilling holes in-situ?

Hasn't that been debunked enough?

The V-1710 was modular, so that the core engine could be configured in different ways - for extension shafts, as a pusher, regular, single stage or two stage supercharger, etc. That is a blessing in someways, but in others it was a downfall. Much time was spent doing these extra options before the engine was fully sorted.




GregP said:


> The original Bell P-39 prototype had a turbosupercharger that was specified by Ben Kelsey and Gordon Saville. Numerous changes were made while Kelsey was busy with P-38 work, and the turbocharger was deleted, making the P-39 a low-altitude fighter that was not suited to Europe’s higher altitude requirements. The P-39 was rejected by the British but was used by the U.S.A. in the Mediterranean and Pacific Theaters, and particularly by the Soviet Union in large numbers. In the P-39, Soviet fighter pilots scored the highest number of individual kills made in ANY US or British fighter type, primarily because the Soviet war was a tactical, short-range, low-altitude war.



The XP-39 with turbocharger was a turd. It never had the performance promised, and likely not even the performance of the modified XP-39 without turbo.




GregP said:


> The Allison V-1710 initially had some issues in Europe. Some of the issues were: 1) Poor intake design (Allison), 2) poor regulation of the turbocharger temperature (GE), different fuel formulation from that used for development (not sure it was anyone's fault). The P-38 also had a very poor cockpit heater, which was a major problem in Europe's higher-altitude environment. Last, one of the biggest issues was poor or almost complete lack of pilot training on good flying practices when entering combat areas. The intake design, fuel issues, cockpit heater, and pilot training were “fixed” within a year, but the temperature regulation of the turbochargers was never really fixed by General Electric.



The problem wasn't really the regulation of turbocharger temperature, but rather regulation of the turbocharger speed, which was controlled using the wastegate. The problem was the wastegate would get stuck closed, sending too much exhaust through the turbine and causing the unit to overspeed.

Fun fact, for an engine designed to be used with the turbocharger, it was a long time before a V-1710 was tested on an engine stand with a turbocharger (1939 or 1938, after the XFM-1 and XP-37 flew with turbos). The aircraft manufacturers just slapped them on.

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## fastmongrel (Apr 5, 2020)

wuzak said:


> And Merlins were hand crafted by fitters using files and feeler gauges and drilling holes in-situ?



Wasn't the Merlin handcrafted in a little shop in Saville Row. When a young gentleman joined the RAF he would travel to London and be measured up for his bespoke Spitfire. "Does Sir wear his supercharger on the left or the right and would Sir like pinstripe camouflage or tweed camouflage for European travel"

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## GregP (Apr 5, 2020)

Hi Wayne,

To address your post above.

1) GE developed the turbocharger at the request of the USAAC/USN, using government money.

2) I clearly stated GE was the sole source if you read it.

3) The US government owned the Allison type certificate. It was also the ONLY V-12 that passed the 150-hour type test during the war. Rolls Royce and others were free to develop their engines as THEY were the owners of the design. The Merlin was privately developed during the Schneider cup races. You know the first Merlin (PV-12) used technology directly from the Rolls Royce Type R engine. The Griffon of 1933 even used the same bore and stroke as the Type R. It was not directly -related to the later Griffons.

4) I never mentioned the Merlin when I said the latest Allison that was flying regularly could make 2,300 hp. You did. Why quote me? Make your own post about the Merlin. It was and IS a good engine and I didn't say different in my post.

5) I didn't say Merlins were hand-crafted with files in the post above. I also never said Merlins were badly built. They weren't.

6) You say the XP-39 was a turd. Many in here have said that. But I have yet to see ONE shred of proof from a flight test that backs it up. What I AM sure of is that if the turbocharger had been retained, the altitude performance of the P-39 would have materially improved. I can't say if it would ever have been a good system since it wasn't developed further than the one installation. Nobody can reliably say how fast it went since the data apparently does not exist or has yet to be uncovered and published.

7) The turbocharger was GFE supplied from GE. If GE didn't fix it, it didn't get fixed. Like the other manufacturers, Allison was not allowed to modify GFE. They bolted it into the airplane and used it. Same with guns and other GFE. When I was in the weapons industry (1980s and 1990s), it was the same then. If you got something from the government, you used it as supplied. If you had GFE issues, you tried to work them out in meetings with the customer and the GFE supplier ... you didn't throw money at a "fix" for which you might or might not get compensated, even IF it got accepted for production. Generally, the users (USAAC pilots and squadrons) would filter back their complaints and the manufacturers would try to work things out as best they could while still turning out products for the war effort.

Not sure what your problem with me is, but it is obvious you don't want to hear anything good about an Allison engine. Too bad, They ARE good engines and run just fine.

Here is Bob Deford's experience with it. He built a Marcel Jurca kit (steel tube fuselage and wood wings). It flies very nicely. He flies over and visits Chino occasionally from Arizona.


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## Shortround6 (Apr 5, 2020)

wuzak said:


> The cost fell with the increase in production. Not really related to any engineering improvements.


To be fair that is not what Greg said. 
"Improvements in manufacturing brought the cost down" 
while a lot of the cost reduction was simply due to mass production some of it was "improvements in manufacturing" which lowered the scrap rates of certain operations, like casting the crankcase and cylinder blocks. Some of it was due to the use of specialized machines which were too large and costly for use for small batches but did reduce costs on large runs. Just lining up more old, small machines with more workers doesn't get you the full benefit of mass production.



wuzak said:


> The XP-39 with turbocharger was a turd. It never had the performance promised, and likely not even the performance of the modified XP-39 without turbo.


Not much argument there. The Performance of the XP-39 was not only well below what what was promised before flight, it was well below what was claimed after flight if in fact such flights at anywhere near the claimed performance ever took place. XP-39 may have been one of the great con jobs of aircraft marketing at the beginning of the war. 



wuzak said:


> The problem wasn't really the regulation of turbocharger temperature, but rather regulation of the turbocharger speed, which was controlled using the wastegate


I am not sure who supplied the turbo charger regulator. It may have been a 3rd party. neither GE or Allison or even the airframe maker. The early one sensed the pressure in the exhaust system and sought to maintain a preset value which in turn was thought to control the inlet pressure (kind of an obvious disconnect here) but it tended to freeze or accumulate ice in the sensor tube and so could stick at any position. Too closed could lead to overspeeding while too open meant the engine never developed rated power at altitude. Not as catastrophic but hardly ideal. This plagued a number of turbo installations, not just the Allison ones. A later regulator sensed the pressure in the intake duct and controlled the waste gate to maintain that preset value. 
Preset in the sense that the engine controls interconnected with the regulator so a certain pressure was supposed to be present at the carburetor intake for a given throttle setting/flight condition without the pilot having to perform any mental gymnastics trying to figure out pressures before carb vs pressure in manifold after carb and engine supercharger.

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## wuzak (Apr 5, 2020)

GregP said:


> 6) You say the XP-39 was a turd. Many in here have said that. But I have yet to see ONE shred of proof from a flight test that backs it up. What I AM sure of is that if the turbocharger had been retained, the altitude performance of the P-39 would have materially improved. I can't say if it would ever have been a good system since it wasn't developed further than the one installation. Nobody can reliably say how fast it went since the data apparently does not exist or has yet to be uncovered and published.



The fact that the XP-39 was whisked off to the NACA wind tunnel for analysis after its first or second flight may be a clue.

Whilst there may not be any shred of evidence from flight test data that the XP-39 was a turd, there is also no flight test data proving the XP-39 wasn't.

The fact that there is no flight test data may be because it probably didn't have any quantitative data taken before it went to NACA to be fixed.

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## wuzak (Apr 5, 2020)

GregP said:


> 3) The US government owned the Allison type certificate. It was also the ONLY V-12 that passed the 150-hour type test during the war. Rolls Royce and others were free to develop their engines as THEY were the owners of the design. The Merlin was privately developed during the Schneider cup races. You know the first Merlin (PV-12) used technology directly from the Rolls Royce Type R engine. The Griffon of 1933 even used the same bore and stroke as the Type R. It was not directly -related to the later Griffons.



I don't know what type tests in the US the Merlin passed. I suspect the Merlin did not have to complete that test because it was a Rolls-Royce design that passed UK type tests.

Even later model V-1650s were built to Rolls-Royce specs and ratings.

The Merlin design started 2 years after the Schneider Trophy was won by the R.

It shared little with the R, if anything.

The 1931 R had a master and slave rod arrangement. The PV12/Merlin had a fork and blade.
The 1931 R had a Kestrel style cylinder head in unit with the block (as the R was based on the Buzzard, which was a 6/5 scale of the Kestrel). The PV12/Merlin started with the blocks and crankcases cast together and a separate cylinder head.
The 1931 R had a flat combustion chamber. The PV12 had the "ramp head".

No doubt that the PV12/Merlin design was informed by the R, but it differed in many key details.

The Griffon I of 1933 was a detuned R.

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## wuzak (Apr 5, 2020)

GregP said:


> 4) I never mentioned the Merlin when I said the latest Allison that was flying regularly could make 2,300 hp. You did. Why quote me? Make your own post about the Merlin. It was and IS a good engine and I didn't say different in my post.



You made the claim that the V-1710 made more power with lower boost. I posted an example that showed that was not always the case.

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## wuzak (Apr 5, 2020)

GregP said:


> 5) I didn't say Merlins were hand-crafted with files in the post above. I also never said Merlins were badly built. They weren't.



When you make the statement:



GregP said:


> There was a high degree of commonality of parts throughout the series and individual parts were produced to high degree of standardization and reliability.



It implies that other engines were not, and that the Allison was somehow special.

None of the major engines could have been produced in the numbers they were if they didn't have "a high degree of commonality of parts throughout the series and individual parts were produced to high degree of standardization and reliability."

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## wuzak (Apr 5, 2020)

GregP said:


> Not sure what your problem with me is, but it is obvious you don't want to hear anything good about an Allison engine. Too bad, They ARE good engines and run just fine.
> 
> Here is Bob Deford's experience with it. He built a Marcel Jurca kit (steel tube fuselage and wood wings). It flies very nicely. He flies over and visits Chino occasionally from Arizona.





I don't have a problem with you.

They may be good engines, but in WW2 they were largely an also ran. Relegated to aircraft that would, for the most part, be considered second tier.

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## Shortround6 (Apr 5, 2020)

GregP said:


> 1) GE developed the turbocharger at the request of the USAAC/USN, using government money.



I am not sure about that, GE was testing turbo superchargers at the end of WW I, not sure if they had a gov contract or not. The Gov sure ordered a number of turbo units from GE during the 20s and 30s. 



GregP said:


> The Merlin was privately developed during the Schneider cup races.


only in the most indirect manner, the races were over with England winning the cup before the Merlin ever got off paper, 



GregP said:


> You know the first Merlin (PV-12) used technology directly from the Rolls Royce Type R engine.


It may have but since the Merlin used a different bore and stroke, different cylinder spacing and a few other things it might also be fair to say it was a scaled up Kestrel, how much it really owes to either engine is subject to question as the first few PV-12/Merlins tended to bounce back and forth on construction features. 



GregP said:


> You say the XP-39 was a turd. Many in here have said that. But I have yet to see ONE shred of proof from a flight test that backs it up.


Trouble is no one can find ONE shred of proof from a flight test that proves it wasn't a turd in it's original form. No one can find the flight test (or the name of the pilot) for when it went 390mph, no one can find the documentation that it actually climbed to 20,000ft in 5 minutes.
We do know that arrangements were being made to ship it to Langley within 4 weeks of first flight. 
We do know that early ground running, taxi tests and early flights were plagued with over heating. 
We do know that due to a suspected drive shaft problem, for which Allison designed and built a new drive shaft, that the XP-39 was not cleared to use more than 2600rpm during the time before it was sent to Langley making any high performance flights highly unlikely. 
We do know that General Arnold was making at least 6 recommendations for modifications to improve performance before the XP-39 ever got to Langley. Some were never implemented, like the suggestion to change to manually operated flaps. Another recommendation was a significant reduction in fuel capacity. Indications that the XP-39 was overweight? Which documentation does show. 

this is for the XP-39 with turbo, no one is saying the later P-39s were anywhere near as bad. But the cry that Langley and the NACA _ruined _the Airacobra doesn't hold up. Larry Bell and his engineers had done that already, Langley and the NACA saved Bell's ass and allowed him to build a fighter that did contribute to the allied war effort.

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## Shortround6 (Apr 5, 2020)

wuzak said:


> I don't know what type tests in the US the Merlin passed. I suspect the Merlin did not have to complete that test because it was a Rolls-Royce design that passed UK type tests.


One of the first Packard Merlin failed to pass it's type test. The US type test was 150 hours, the British test was 100 hours, there were a few other differences. The Merlin failed betten 100 hours and 150 hours. some where there are details. While the Allison had passed a type test back in 1936/37? it was a rather different engine than the C series engine used in the Tomahawks (which actually failed multiple times before getting sorted out. Part of the problem was the test stand failed to dampen any vibration like an actual aircraft frame would), Every version had to pass either a type test or a model test, you can't make a major change (like stick the P-39 extension shaft on the front) without doing another test. Any change in engine power rating needs another test. Change crankshaft? another test, the government is not going to take Allisons word (or any other companies word) that the new crankshaft is better than the old one. 
It took months to get the -93 Allison used in the P-63 through it's test.

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## Reluctant Poster (Apr 6, 2020)

Who is manufacturing all these Allison’s? The Allison wasn’t produced in serious quantaties until 1941
Deliveries of V-1710
1939 0
1940 1149
1041 6409

As far as Allied engines go the Merlin was pretty much the only game in town for the first part of the war. If the Battle of Britain was fought with American equipment it would have been P-35s and 36s. And even P-26 s.


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## tomo pauk (Apr 6, 2020)

Reluctant Poster said:


> Who is manufacturing all these Allison’s? The Allison wasn’t produced in serious quantaties until 1941
> Deliveries of V-1710
> 1939 0
> 1940 1149
> 1041 6409



Allison did the manufacturing of V-1710s, with some GM-owned parts' supplies (Cadillac, for example).



> As far as Allied engines go the Merlin was pretty much the only game in town for the first part of the war. If the Battle of Britain was fought with American equipment it would have been P-35s and 36s. And even P-26 s.



American 'early war' and British 'early war' were not the same thing.


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## Reluctant Poster (Apr 6, 2020)

tomo pauk said:


> Allison did the manufacturing of V-1710s, with some GM-owned parts' supplies (Cadillac, for example).
> 
> 
> 
> American 'early war' and British 'early war' were not the same thing.


“Could the Allison have done what the Merlin did?” was the question. The answer is no. It could not have fought the Battle of Britain.

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## tomo pauk (Apr 6, 2020)

Reluctant Poster said:


> “Could the Allison have done what the Merlin did?” was the question. The answer is no. It could not have fought the Battle of Britain.



Why resort to pulling things out of context? Here is what OP was asking, I've bolded actual questions:



CobberKane said:


> Okay, here's one for the technophiles (definitely not including me). The Allison engine in it's various guises has always seemed to play second fiddle to it's famous contemporary in the land of hope and glory, the Merlin. *Was there any intrinsic design feature that precluded Allison engines from powering single engine fighters over Germany at 25000 feet, of was it all just a case of the American engine being hobbled by the thinking of the time - that high altitude fighters weren't required?*
> To get full marks, please include an objective comparison of the beers of both countries.



Nowhere in the OP is required that V-1710 takes part in the BoB, the actual questions are about why the V-1710 was lacking the power at high altitudes etc, unlike what Merlin did.

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## Shortround6 (Apr 6, 2020)

And the answer is that there was nothing wrong with engine, it was the supercharger setups that were lacking. A Merlin III would have nearly useless over Germany at 25000ft in late 1943/44.

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## Reluctant Poster (Apr 6, 2020)

tomo pauk said:


> Why resort to pulling things out of context? Here is what OP was asking, I've bolded actual questions:
> 
> 
> 
> Nowhere in the OP is required that V-1710 takes part in the BoB, the actual questions are about why the V-1710 was lacking the power at high altitudes etc, unlike what Merlin did.


Point taken. I should have read the original question.

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## Reluctant Poster (Apr 6, 2020)

Shortround6 said:


> And the answer is that there was nothing wrong with engine, it was the supercharger setups that were lacking. A Merlin III would have nearly useless over Germany at 25000ft in late 1943/44.


There were more issues than the poor supercharging. 
In late 1943 early 1944 the V 1710 had severe oil consumption problems at altitudes over 20,000 feet. Freeman mentions this in his books and Whitney discuses it in Vee for Victory. The problem was severe enough that the MTO command was recommending substituting V1710-55/56 for -89/91 In their F-5Bs. Whitney states that it was solved later in the year.
Improved supercharging still does not solve the excessive pressure losses and fuel distribution problems caused by the very poor intake manifold design. The ”Madame Queen“ intake Venturi is literally a second carburetor required to suck up the fuel that collected in the intake and reintroduce it into the airstream. This is a further cost in pressure loss. No other engine required this fix.
As pointed out by Jerry Wells in his article in the Torque Meter the single block Merlins were significantly different from the later engines. He went so far as to dub the earlier engines as Super Kestrels. He also points out the the V-1710, like the early Merlins, is not a true monoblock engine, in that the cylinder liners are not divorced from the crankcase but are subjected to the distortions from the crankcase. He believes this is a limitation on the power that could be produced by the Allison. Note that the trapped flange method of retaining the cylinder liner became the standard for high performance wet sleeve engines after WWII, with the best example being the most successful racing engine of all time the Cosworth DFV.


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## swampyankee (Apr 6, 2020)

Some of the V-1710 problems were installation-related, such as many of the problems in the P-38 (this was due to the rather inane assignment of the turbocharger system to the airframe maker, not the engine maker. The same assignment of responsibility caused problems with the AGT1500 installation in the M1 Abrams 30 years later. One would think they would have learned).


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## Shortround6 (Apr 6, 2020)

Why was the engine have severe oil consumption? major flaw in the engine or something weird going on with the crankcase breathers? 
I seem to remember something about cutting the ends of the breather tubes at a different angle solving the problem? 
A certain altitude and speed combination almost acting like syphon and sucking oil laden air out of the crankcase? 



Reluctant Poster said:


> The ”Madame Queen“ intake Venturi is literally a second carburetor required to suck up the fuel that collected in the intake and reintroduce it into the airstream. This is a further cost in pressure loss. No other engine required this fix.




There were only two allied V-12s operating at high altitudes that might require such a "fix" as the Madame Queen intake manifold. The radials used much shorter intake pipes and were either individual or paired? so such a device was not needed, Russian engines used a carburetor for every pair of cylinders so again, no long intake manifold to cause problems. Yes the Allison had a problem but you are rather over stating the case. 
Problem also showed up when the Allies introduced a new fuel specification. It did two things. It allowed the use of 4.3 cc of lead per gallon instead of the previous 4.0 cc of lead (which had been changed from 3.0ccs of lead) all for 100/130 fuel. It also allowed the increased use of heavier aromatic compounds to blend the fuel than the previous specifications. This allowed for greatly increased output of 100/130 fuel from the same tonnage of crude. It also reduced the volatility of the fuel ( how well it evaporated and stayed evaporated in cool air).
Again, engines with long intake passages are going to be the most affected. Since only two stage engines used intercoolers all single stage engines had pretty hot intake mixtures and rarely ran into problems. Which leaves the Merlin and the Allison, it turns out the Merlin was not immune from this problem. In post war use on transports they ran into a cold mixture problem which was solved by reversing the coolant flow (valves were added to control this) so they actually heated the air in the "intercooler" when cruising at low power settings. 
Again this problem was somewhat (but not entirely) supercharger set up dependent. The Turbo Allison being about the only V-12 where the pilot could "select" how much boost was being provided by the turbo and how much was being provided by the engine supercharger. He didn't do this directly (or even knowingly) but by selecting different RPM and throttle settings for the needed power at cruise quite different use was made of the turbo and intercooler system resulting it in a wide variation of possible intake mixture temperatures. A lot of bad "advice" was given to pilots on how to the fly the P-38 which added to the problem, advice that was was in direct contradiction to how Lockheed and Allison were saying the plane should be flown yet Allison gets the blame? 
Unfortunately this system also required skilled/knowledge set up and maintenance. It seems the turbo controls were often miss rigged, causing higher than normal speeds and higher pressure/velocity at the carb leading to lean conditions. There was a hydraulic turbo control on the earlier planes with an electric control on the later ones. The early one was rather easy to adjust. the later one took a refit kit. 

Again, all of this was "stuff" on the outside of the basic engine. It did greatly affect the reliability of the engine but was not an inherent defect in the basic engine or it's design. 
Properly sorted out Allisons were quite capable of running at high power levels for considerable periods of time.

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## fastmongrel (Apr 6, 2020)

swampyankee said:


> One would think they would have learned).



Nope never going to happen 😒


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## Shortround6 (Apr 6, 2020)

swampyankee said:


> Some of the V-1710 problems were installation-related, such as many of the problems in the P-38 (this was due to the rather inane assignment of the turbocharger system to the airframe maker, not the engine maker. The same assignment of responsibility caused problems with the AGT1500 installation in the M1 Abrams 30 years later. One would think they would have learned).



I am not even sure how much was Lockheed's fault. Government comes along and says, "here's your engine, here's your turbos and btw here's your turbo regulator, now you fit them together and make them work".
There were at least two and possibly 3 different turbo regulator setups. 1st on sensed the back pressure in the exhaust duct near the turbine on the turbo and tried to keep that at a certain value. This design philosophy was the Army's, not Lockheed's. This was supposed to by extension (and wishful thinking) maintain a constant pressure (sea level) at the intake to the carburetor. Unfortunately it caused a number of problems, like excessive back pressure, rough running and slow (sometimes non existent) control over the intake pressure. I am not sure if the electric control was the first one to measure the intake pressure and control the exhaust wastegate accordingly or if there was an intermediate step. 
The government was supplying the engines, turbos and turbo regulators for the P-43 and P-47, the B-17, the B-24 and the B-29 and other experimentals.


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## gjs238 (Apr 6, 2020)

Shortround6 said:


> ... Langley and the NACA saved Bell's ass and allowed him to build a fighter that did contribute to the allied war effort.


Wonder if Bell's resources could have been better used manufacturing [fill in the blank] under license.


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## tomo pauk (Apr 7, 2020)

gjs238 said:


> Wonder if Bell's resources could have been better used manufacturing *P-40* under license.



There you go.

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## swampyankee (Apr 7, 2020)

Shortround6 said:


> I am not even sure how much was Lockheed's fault. Government comes along and says, "here's your engine, here's your turbos and btw here's your turbo regulator, now you fit them together and make them work".
> There were at least two and possibly 3 different turbo regulator setups. 1st on sensed the back pressure in the exhaust duct near the turbine on the turbo and tried to keep that at a certain value. This design philosophy was the Army's, not Lockheed's. This was supposed to by extension (and wishful thinking) maintain a constant pressure (sea level) at the intake to the carburetor. Unfortunately it caused a number of problems, like excessive back pressure, rough running and slow (sometimes non existent) control over the intake pressure. I am not sure if the electric control was the first one to measure the intake pressure and control the exhaust wastegate accordingly or if there was an intermediate step.
> The government was supplying the engines, turbos and turbo regulators for the P-43 and P-47, the B-17, the B-24 and the B-29 and other experimentals.



It's certainly a complex question to answer. My experience with military project managers (I worked in the defense industry during the Carter, Reagan, and GHW Bush administrations) was that they wildly varied in competence. Interestingly, high-profile, highly classified programs tended to be worst (find a Sikorsky engineer who worked on the X-wing program. Get [almost certainly] him a little tipsy and ask about how the program was run....). UTTAS -- the program that led to the H-60 series -- was generally considered to be the best run. The others were somewhere between. Interestingly, from when I was at Sikorsky (I was *not *involved, except very peripherally, with the X-wing. Thank God), the USMC was considered to have the best project offices, although I don't know how they were defining "best."


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## Koopernic (Apr 7, 2020)

GregP said:


> Some posted info is not consistent with my experience.
> 
> The early impellers were 8.25 inch, later they went to 9.5 inch, and in the G-6 and later engines they were 10.25 inch impellers. The impellers were NOT too small. The US government required Allison to use the turbosuperchagers (called turbochargers today) as the high-altitude boost system. As such, the normal supercharger impeller was supposed to handle things up to about 15,000 feet, which it did even in the 8.25 inch form.
> 
> ...



What was the US Government thinking in not funding a 2 stage supercharger for the V-1710? It would have been relatively risk free.


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## swampyankee (Apr 7, 2020)

Koopernic said:


> What was the US Government thinking in not funding a 2 stage supercharger for the V-1710? It would have been relatively risk free.



Its experts in the USAAC didn't ask them to. Somewhere in the War Department, where the civilian leadership is in direct contact with the military leadership, somebody made a decision that turbocharging was _the _way to go and that efforts to develop two-stage, mechanically driven superchargers were pointless. Whether this decision was made by people in uniforms, civil servants in the War Department, turbo enthusiasts in patronage positions in the Executive Branch (who seemed exclusive to the War Department, so I don't think this is any sort of top-down push from the White House), or heavily lobbied (and possibly bribed) members of the House and Senate (again, it doesn't seem to have existed in the Navy Department, so I don't think it's a push from the legislature) can only be determined by somebody spending a lot of time in archives.


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## gjs238 (Apr 7, 2020)

CobberKane said:


> Okay, here's one for the technophiles (definitely not including me). The Allison engine in it's various guises has always seemed to play second fiddle to it's famous contemporary in the land of hope and glory, the Merlin. Was there any intrinsic design feature that precluded Allison engines from powering single engine fighters over Germany at 25000 feet, of was it all just a case of the American engine being hobbled by the thinking of the time - that high altitude fighters weren't required?
> To get full marks, please include an objective comparison of the beers of both countries.



Good question.
Specifically, did the intrinsic design of the V-1710 preclude development of it's supercharger in the ways that the Merlin supercharger developed?
Multi-speed, multi-stage, water cooling, etc.


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## Shortround6 (Apr 7, 2020)

Conspiracy theories aside, there were some practical reasons that war dept may not have pushed for two stage superchargers.

One was that GE, makers of turbochargers, was the design headquarters for mechanical superchargers for P & W and Wright (and anybody else) in the US for the 1920s and most engines in the 20s didn't use superchargers or least not ones with very high boost. What would evolve into superchargers on radial engines were sometimes referred to as "mixing fans" and turned at low rpm (sometimes crankshaft speed?) and helped mix the fuel/air after the carb and help insure that the top cylinders got the same mixture as the bottom cylinders. Sometimes they used enough rpm on the fan to recover the pressure loss through the carb and plumbing. That is they actually had 29.95 inches at the intake valve instead of 27in or so of pressure. 
When you have fuel of 70 octane or less using high boost is impossible without going into detonation. A single stage supercharger could provide all the altitude performance the engine could stand.
The War dept didn't become interested in high altitude flight for some time. At least to the extent of funding more than few experiments. During the 20s they were still trying to figure out oxygen systems and rudimentary cockpit heating (or at least well insulated flying suits.) 






Please remember that it just wasn't the absolute pressure in the manifold that lead to detonation it was also the temperature of the mixture. HIgher octane fuel withstands higher temperature before self igniting. So at high altitude with poor fuel it didn't matter if your manifold pressure was low if the mixture temperature was high, you still got detonation. 

This is all background, once you get to the 30s things do start to change but now you are starting to run out of time. GE superchargers weren't really very good. Since they had more than enough power to drive them when using a turbo they never really looked at the efficiency of the compressor. And when they were using 70,77, 80 octane fuels they could not use much boost anyway, the the inefficiency and heat rise of the poor compressors was masked. It wasn't until 1937-38 that P & W and Wright finally figured out the GE supercharges they were buying weren't that good. Now you had 2-4 years to not only design their own single stage superchargers but try to come up with a two stage mechanical design? Which P & W did. 
The whole turbo idea was sold as allowing the engine to develop sea level power at 15,000-25,000ft (depending on the year) by the turbo supplying sea level air pressure to the carb and keeping the back pressure on the exhaust valves at a near to sea level value (they never really managed this). This also meant the turbo engine didn't have to be built any stronger than the normal engine/s (same internal pressures) or need any additional cooling (except for the need to cool at the higher altitudes)
The mechanical two stage supercharger doesn't have those sales points. The power to drive the second stage comes from the engine itself so you either get less power to the prop than the turbo equipped engine or you need an engine that is making more power in the cylinders and needs heavier construction and better cooling (air or liquid flow) around the cylinders. 

Somebody once said that with two stage superchargers the 2nd stage multiples any mistakes in the first stage design. An inefficient 1st stage with a large heat rise feeding a 2nd stage means some really high intake mixture temperatures (one reason just about all US turbo equipped planes used intercoolers).

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## Snowygrouch (Apr 7, 2020)

Shortround6 said:


> Somebody once said that with two stage superchargers the 2nd stage multiples any mistakes in the first stage design. An inefficient 1st stage with a large heat rise feeding a 2nd stage means some really high intake mixture temperatures (one reason just about all US turbo equipped planes used intercoolers).



This is correct, the efficiency of the 1st stage is the most critical, and poor 1st stage performance is multiplied by each subsquent stage. They do not add, they multiply; its just that often the efficiecies are so low that from inspecting the total pressure ratio of a 2-stage compressor, its easy to think its added (e.g Merlin-61 total PR is about 6:1, but from the individual 
stages you might expect nearer 8 or 9 if multiplied - hence an easy mistake to make.).

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## rinkol (Apr 7, 2020)

gjs238 said:


> Good question.
> Specifically, did the intrinsic design of the V-1710 preclude development of it's supercharger in the ways that the Merlin supercharger developed?
> Multi-speed, multi-stage, water cooling, etc.


The basic V-1710 mechanical supercharger seems to have been constructed so that the crankcase made up part of the supercharger housing. As far as I can tell, a mjor redesign would have been needed to install a two speed drive.


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## Reluctant Poster (Apr 8, 2020)

Shortround6 said:


> Why was the engine have severe oil consumption? major flaw in the engine or something weird going on with the crankcase breathers?
> I seem to remember something about cutting the ends of the breather tubes at a different angle solving the problem?
> A certain altitude and speed combination almost acting like syphon and sucking oil laden air out of the crankcase?
> 
> ...



The Merlin's issues with plug fouling at cruise were in no way comparable to the severity of the problems the Allison had. In any event the Merlin's charge heating system actually turned out to be an unnecessary complication.
Alec Harvey Bailey describes the course of events in his book “The Sons of Martha”.
“BOAC wanted an aircraft of greater all-up weight, entailing more take-off power. On 100 octane fuel this presented a difficulty, whereas two-stage military engines had full depth intercooling, the civil versions had half the intercooler casing given over to afterheating, to raise the charge temperature at cruise and avoid plug leading. This had been a TCA requirement following their experience with single-stage engines on the Atlantic, which had shown the need for charge heating. With half depth intercooling the charge temperature would be higher at take off with some loss of power and at 20 lb boost would be close to detonation. Design came up with the mixing scheme, which allowed intercooling at take-off and charge heating at cruise by bleeding engine coolant into the intercooler system. The reduced charge temperature thus achieved at take-off, plus a shade more boost, allowed the power to be increased from 1720hp to 1765hp, enabling the desired increase in weight.”
A spate of intercooler pump failures ensured. The pumps, as it turned out, had always leaked to some extent.
“Forced to reappraise the mixing scheme, which had contributed to my problem, it was shown that at cruise powers the charge temperature was sufficient to avoid plug leading without charge heating. By deleting the mixing scheme and using full intercooling for take-off and zero intercooling at cruise by putting a stop valve in the circuit, the requirements of the operation were met.”
The Merlin 724 was built that way from the start.


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## Reluctant Poster (Apr 9, 2020)

I realize I harp on the Allison’s poor intake design, but the truth is that Allison should have known better.
Prior to computers taking over the task, engineers in the USA and Canada used Crane Technical Paper No 410 “Flow of Fluids though Valves, Fittings and Pipe” to calculate pressure drops in piping systems. I have the May 1942 version of this paper (first edition was 1935) which gives us an idea of the state of the art at that time.










It is easy to calculate pressure drops in a straight run of the pipe, the tricky bit is determining the effect of splits in flows, changes in direction and discontinuities such as valves. Crane came up with the brilliant concept of equivalent length where you convert the effect of a fitting into a length of pipe. Figure 17 is the nomograph used to determine the equivalent length of various fittings.
I don’t have the dimensions for the Allison intake. But let’s assume it’s a 3” dia pipe with a length of 5 feet. Each short radius elbow (and the Allison elbows are very short) is the equivalent of 8 feet of pipe. To get to the mini plenums at each group of 3 cylinders there are 3 very abrupt elbows. Actually, it is even worse than that. One of the big no-nos in piping design is back to back elbows. The delta P of back to back elbows is difficult to calculate but it can be safely said that it is worse than the simple sum of the two. The two elbows that direct the air towards the rear of the engine could be modelled as a close return bend with an equivalent length of 20 feet, but the two elbows in Z formation would be worse. Throw in 2 splits in flow and you can see how much of the work done by the compressor is wasted.
In contrast the Merlin (single stage) seems to have a bigger pipe to begin with, which obviously reduces losses, but also notice how smoothly the discharge of the compressor transitions to the inlet of the plenum. A graceful sweeping curve which is so gradual that its pressure drop will be basically equivalent to its length. Note that the discharge of the compressor is tangential to the rotor preserving the direction of flow. From the plenum there are branches leading to each plenum at the cylinders. I would model these as an ordinary entrance loss, which for a 3” pipe is equivalent to about 5 feet of pipe.
Overall the Allison intake looks to have quadruple the pressure loss of the Merlin’s.

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## BAGTIC (Apr 9, 2020)

CobberKane said:


> Okay, here's one for the technophiles (definitely not including me). The Allison engine in it's various guises has always seemed to play second fiddle to it's famous contemporary in the land of hope and glory, the Merlin. Was there any intrinsic design feature that precluded Allison engines from powering single engine fighters over Germany at 25000 feet, of was it all just a case of the American engine being hobbled by the thinking of the time - that high altitude fighters weren't required?
> To get full marks, please include an objective comparison of the beers of both countries.




This source


CobberKane said:


> Okay, here's one for the technophiles (definitely not including me). The Allison engine in it's various guises has always seemed to play second fiddle to it's famous contemporary in the land of hope and glory, the Merlin. Was there any intrinsic design feature that precluded Allison engines from powering single engine fighters over Germany at 25000 feet, of was it all just a case of the American engine being hobbled by the thinking of the time - that high altitude fighters weren't required?
> To get full marks, please include an objective comparison of the beers of both countries.


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## BAGTIC (Apr 9, 2020)

CobberKane said:


> Okay, here's one for the technophiles (definitely not including me). The Allison engine in it's various guises has always seemed to play second fiddle to it's famous contemporary in the land of hope and glory, the Merlin. Was there any intrinsic design feature that precluded Allison engines from powering single engine fighters over Germany at 25000 feet, of was it all just a case of the American engine being hobbled by the thinking of the time - that high altitude fighters weren't required?
> To get full marks, please include an objective comparison of the beers of both countries.



This source suggests that the failure to develop a better turbo-supercharger was based or prioritization of tungsten for other purposes. This is in keeping with other things I have read about very high priority being given to use of tungsten in machine tools in order to maintain high industrial production.

Allison V-1710 Engine


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## Reluctant Poster (Apr 9, 2020)

BAGTIC said:


> This source suggests that the failure to develop a better turbo-supercharger was based or prioritization of tungsten for other purposes. This is in keeping with other things I have read about very high priority being given to use of tungsten in machine tools in order to maintain high industrial production.
> 
> Allison V-1710 Engine


American tanks were rationed in their use of HVAP ammunition (tungsten cored) for the same reason.


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## tomo pauk (Apr 9, 2020)

BAGTIC said:


> This source suggests that the failure to develop a better turbo-supercharger was based or prioritization of tungsten for other purposes. This is in keeping with other things I have read about very high priority being given to use of tungsten in machine tools in order to maintain high industrial production.
> 
> Allison V-1710 Engine



Unfortunately, some of claims require a truckload of salt so we can digest them. Like:
_The few turbo-supercharged Allisons that were made, were allocated to  P-38s, making the high-altitude performance of that plane its best feature. _

There was not a 'few of turbo-suercharged Allisons' made, but around 20000 thousand (there was more than 10000 P-38 produced). To put the number of 20000 in perspective, this is about as much of Spitfires produced, or Fw 190s produced. Or, almost 50% more than what P-40 production needed when it is about the engines. Trick might be that turbo installation on the P-38 actually worked, while on the Curtiss and Bell prototypes did not?

Then:
_Donaldson R. Berlin, the  P-40's  designer, has said that  P-40s  experimentally equipped with turbo-superchargers outperformed  Spitfires  and  Messerschmitts  and that if it had been given the engine it was designed for, the  P-40  would have been the greatest fighter of its era. _

There is no picture, diagram or flight test of a P-40 that was experimentally equipped with turbo-superchargers, 75-80 years after the supposed aircraft was supposedly outperformed those two fighters (of what version - that we also don't know). Perhaps due to the simplest reason: there was no such P-40s?

Further:

_It wasn't until the XP-40Q was modified with a "bubble" canopy, cut-down rear fuselage, wing radiators, clipped wing tips, a four-blade propeller, water injection and weight reduced to 9,000 lb that the XP-40Q attained a maximum speed of 422 mph. _

Nowhere in the article is mentioned that XP-40Q that did 422 mph was outfitted with a 2-stage supercharger. Bubble canopy and better prop can't earn 30-40 mph. 9000 lb heavy P-40 is not a sign of weight reduction, but of gaining the weight.

Nowhere in the article is said that there was a 'failure to develop' better turboes due to the lack of tungsten.



Reluctant Poster said:


> American tanks were rationed in their use of HVAP ammunition (tungsten cored) for the same reason.



Do we have a good source for that?


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## Shortround6 (Apr 9, 2020)

tomo pauk said:


> Nowhere in the article is said that there was a 'failure to develop' better turbos due to the lack of tungsten.



One might also note the tens of thousands (if not hundreds of thousands) of turbochargers used on bombers. Like eight on every B-29. we are are also confusing quality (_better_) with quantity. American tubos did get better as the war went on, able to run several thousand rpm faster than early ones. 
See; https://www.enginehistory.org/Turbochargers/GETurbochargerData.jpg 



tomo pauk said:


> Do we have a good source for that?


It is pretty well known, most US tanks had 2-5 rounds of HVAP as official load if they had 76mm guns. Ammunition supply sometimes did not allow this.The Shermans with 75mm guns didn't get any HVAP. At the velocities the 75mm gun operated at they thought the increase in penetration would be marginal, still won't got through the front of a Panther or Tiger.


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## Navalwarrior (Apr 9, 2020)

Koopernic said:


> If Britain faced a shortage of Merlins it could theoretically have powered the Lancaster, Wellington, Halifax & Beaufighter with the Allison. It was a while before the two speed superchargers were used on the Merlins I believe.
> 
> The turbo-charged Allision probably could have been fitted to these British bombers. A Turbo charged Allison on a Lancaster might give it quite a good altitude performance, perhaps as good as the Liberator.
> 
> ...


Resp:
The USN used an inline aircraft engine in their PT Boats.


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## Navalwarrior (Apr 9, 2020)

wuzak said:


> I don't have a problem with you.
> 
> They may be good engines, but in WW2 they were largely an also ran. Relegated to aircraft that would, for the most part, be considered second tier.


Resp:
The post WWII production F-82 used the Allison engine, as the Packard Merlin production license was about to expire. The F-82 had outstanding performance.

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## Reluctant Poster (Apr 9, 2020)

tomo pauk said:


> Unfortunately, some of claims require a truckload of salt so we can digest them. Like:
> _The few turbo-supercharged Allisons that were made, were allocated to  P-38s, making the high-altitude performance of that plane its best feature. _
> 
> There was not a 'few of turbo-suercharged Allisons' made, but around 20000 thousand (there was more than 10000 P-38 produced). To put the number of 20000 in perspective, this is about as much of Spitfires produced, or Fw 190s produced. Or, almost 50% more than what P-40 production needed when it is about the engines. Trick might be that turbo installation on the P-38 actually worked, while on the Curtiss and Bell prototypes did not?
> ...


I was wrong about the ammunition . It seems that by mid 1943 there were ample supplies of tungsten.
According to ”Study of Experience in Industrial Mobllization in World War II”:
”From a critical position in 1941 tungsten moved to a position of adequate supply in 1944. But tungsten was under strict priority and allocation control from March 1941 to July 1943. The new supply so increased that after August 1943 most dealers could purchase without priorities.”
I do know that that HVAP was in short supply. Major Paul Bane: “ However, at no time have we able to secure more than five rounds per tank and in recent actions this has been reduced to a maximum of two rounds, and in many tanks all this type has been expended without being replaced. “ as quoted in “ M4 Sherman at War”

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## Reluctant Poster (Apr 9, 2020)

Navalwarrior said:


> Resp:
> The post WWII production F-82 used the Allison engine, as the Packard Merlin production license was about to expire. The F-82 had outstanding performance.


The outstanding performance was by the Packard engined version. The famous long distance flight was Merlin powered. The Allison powered version was slower and had a lower rate of climb, when it was actually working.
The following quotes are from ” Mustang Designer”:
’As the Air Force Historical Office case history explained in great detail, “The major problem in the F-82 program was the failure of the government furnished engine.”’
‘33 hours of maintenance were required for each hour flown.’
’Persistent engine problems kept over 50 percent of these planes out of commission during most of 1949.’
’When working right, which was seldom...’

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## ThomasP (Apr 9, 2020)

Hey guys,

On the subject of the use of tungsten in the WWII turbos. Do we know if there was any tungsten actually used in the US turbos? I ask because as far as I see it there would be no need for it, and there were no applicable(?) alloys (as far as I know) in existence at the time.

The reason that I say this is an alloy such as Stellite would be far easier to use in the high temperature environment of the turbo. At the time (late-1930s) it could be cast into complex shapes, hot drawn and forged, and electroplated in relatively thick layers. Stellite is a cobalt based alloy - there is no Tungsten used.

Otherwise, for tungsten, the only useful alloys (I think) available at the time would be the tool steels in the T series (T2 and T4 for example) but fabricating the shapes needed for the turbos would be very difficult, probably not really feasible at the time, and if you could make them they they would be enormously expensive. As far as i can imagine, the only possible practical use in a turbo might be for bushings or bearings. But, again there are other materials that would be more usable (EG Stellite and M series tool steels). Also, if Tungsten based tool steel was used, the amount of tungsten used in the alloys would not have been enough to interfere with the production of HVAP. The amount of tungsten used in tungsten-carbide cutting tools, however, might have been enough to do so.

I believe that GE (and others?) concentrated on early titanium alloys, the temperature resistance (not as high as tungsten alloys or Stellite) was high enough, at least in theory. Titanium bearing ore was difficult to process at the time, and manufacturing it was also difficult, plus extreme temperature cycles (such as in turbos) would have caused cracking in most of the alloys available at the time.

Having said all the above, I thought that the main problem was simply inexperience with the complex problem of very high temperatures combined with wear of the bushing/bearing surfaces at extremely high rpm.

I admit that I am not intimately familiar with the materials used for the various parts of the WWII GE turbos. Does any one have info on what parts used tungsten alloys? I would appreciate the info.


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## tomo pauk (Apr 9, 2020)

All in all, it was more convinient to blame it to other people (like accusing the British for their fuel - their fuel???) or to the circumstances (supposed lack of tungsten), instead of admitting that neither Curtiss nor Bell designed a honest turboed aircraft until too late (if ever), or to admit that intake manifold on V-1710 was not well designed, or that there was a fault in training when switch was made from P-38s with low-capacity intercooler to the P-38 with decent intercooler.

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## swampyankee (Apr 9, 2020)

.


Navalwarrior said:


> Resp:
> The USN used an inline aircraft engine in their PT Boats.



Yes, but not an Allison in production boats. They also looked at using the V-3420 in an enlarged PT boat


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## Snowygrouch (Apr 9, 2020)

ThomasP said:


> I admit that I am not intimately familiar with the materials used for the various parts of the WWII GE turbos. Does any one have info on what parts used tungsten alloys? I would appreciate the info.



The GE "B2" turbo gas turbine impeller blade composition was:

19.7% Nickel
12.7% Chromium
2.57% Tungsten
0.77% Silicon
0.72% Molybdenum
0.59% Manganese
0.5% Carbon

bal: Fe

Most of the pressings etc are Inconel, so basically Nickel-Chrome and a little Iron (no tungsten).

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## GregP (Apr 9, 2020)

Regarding post #104, the supercharger was not a part of the crankcase. There was a center power section that had a crankcase, the main bearings - pistons & rods. There was a nose section. The nose section was either an F/G-type nose with an SAE 50 spline prop shaft or an E-Type remote drive, as used by the P-39 and PT boats, etc. The third section was the supercharger section, commonly called the auxiliary section. It mated to the crankcase, to be sure, but the design of the supercharger could have easily changed and still could have mated to the power section. The carburetor mounts to the top of the impeller and the fuel nozzle ends in a small cone with a flat top. Fuel hits the round flat top and atomizes in a conic cloud that goes directly into the impeller center. It is compressed centrifugally and then enters the intake manifold tub where it splits in the middle and then turns upward where it splits again into four 3-cylinder manifolds. 

The supercharger could have changed anytime, and eventually did. They went from a 9.5" impeller to a 12.25" or a 12.18" impeller late in the series. To be specific, the first Allison (numerically by dash number) that had the larger impeller was the V-1710-97, which was the first of the G-series engines. The engine had a 9.60 : 1 gear ratio, the auxiliary section had a 7.485 : 1 gear ratio, and the propeller gear ratio was geared down 2.36 : 1.

The 12.18" impellers were in the -125 and -127 engines.


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## Shortround6 (Apr 9, 2020)

Navalwarrior said:


> Resp:
> The USN used an inline aircraft engine in their PT Boats.




Yes and no.

The Packard M-2500 was a marine engine developed from a 1920s aircraft engine. The aircraft engines pretty much maxed out at about 800hp at 2000rpm supercharged and while a few were supercharged they were very rare. Engine went about 1200lbs. depends on reduction gear. and supercharger, could hit 1600lbs depending on version.

The more common boat engine, the 4M-2500 was rated at 900hp at 2000rpm continuous. 1200hp at 2400rpm for one hour out of 25 and for emergency use only 1350hp at 2500rpm restricted to 15 minutes in one 10 hour period. The engine and reversing gear (includes clutch) with perhaps exhaust manifolds (?) went 2950lbs. I have no idea how much the reversing gear weighed. Starter and generator may also have been included? 
Engine construction was a bit strange for 1940 but very common in the 1920s. Each cylinder was a individual tube closed on one end with the valve seats in the closed "head" of the cylinder. A stainless steel water jacket was welded around each cylinder, a "valve housing" ran the length of all six cylinders and held the valve mechanism The over head cam, rocker shafts, rocker arms valves springs, etc. It was one piece made out of aluminium and was interchangeable left to right. Just turn it around so the inlet side was inside the V. 
So far I have not found a manifold pressure. 
USN manuals can be found on line. 

I have no idea what was changed between the aircraft versions and the Marine versions.

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## wuzak (Apr 9, 2020)

GregP said:


> The supercharger could have changed anytime, and eventually did. They went from a 9.5" impeller to a 12.25" or a 12.18" impeller late in the series. To be specific, the first Allison (numerically by dash number) that had the larger impeller was the V-1710-97, which was the first of the G-series engines. The engine had a 9.60 : 1 gear ratio, the auxiliary section had a 7.485 : 1 gear ratio, and the propeller gear ratio was geared down 2.36 : 1.
> 
> The 12.18" impellers were in the -125 and -127 engines.



The 12.25" and 12.18" impellers were for the auxiliary stage of the 2 stage supercharger.

The main/engine stage remained 9.5" for the duration of the war.

There were a couple of experimental 2 speed single stage engines that used a 10.25" supercharger impeller, but these did not make production.

10.25" is the same diameter as the supercharger impeller on the bulk of Merlin single stage engines.

Most Merlin 2 stage engines had superchargers of 12.0"/10.1" diameter, with early versions using 11.5"/10.1". 

The RM.17SM, which passed the type test but was never produced or given a dash number, had larger supercharger impellers of 12.7"/10.7".

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## ThomasP (Apr 9, 2020)

Thank you for the info SnowyGrouch.

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## Reluctant Poster (Apr 10, 2020)

ThomasP said:


> Hey guys,
> 
> On the subject of the use of tungsten in the WWII turbos. Do we know if there was any tungsten actually used in the US turbos? I ask because as far as I see it there would be no need for it, and there were no applicable(?) alloys (as far as I know) in existence at the time.
> 
> ...




The statement that Stellite does not contain Tungsten is not true, some varieties do, for example Stellite 6 contains 4-6% Tungsten. From what I have been able to ascertain early turbos used Stellite 6 for their blades , however the bulk of production used Stellite 21 which does not contain Tungsten and has the advantage of being able to be cast, which greatly simplified blade production. See the following link

Our Company History

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## Reluctant Poster (Apr 10, 2020)

Continuing my harping.
One of the improvements suggested by NACA in the attached paper replaces the pipe joining the two supercharger stages with a lower pressure drop design.




View attachment 576951





As you can see the bends in the NACA design are much more gradual. According to the NACA tests, this simple change increased power by 10 HP. If two badly designed elbows can cost that much horsepower think of how much power was wasted in the Allison's convoluted intake manifold. I amazed that Allison still didn't understand flow at this late a stage.

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## fastmongrel (Apr 10, 2020)

That is a horrible tight bend on the standard duct I have seen ride on mowers with better intakes


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## GregP (Apr 10, 2020)

Hi Wayne,

When the supercharger impellers come in 2 sizes, it was obviously a 2-stage engine.

As you know from visiting here, Joe has a couple of 10.25" superchargers in his inventory. They fit the standard V-1710 crankcase.

In the picture above, you can see the more gradual turn doesn't fit in the same vertical space. So, as long as you HAVE that room, you can make the change. If you don't have that room, you can't. If it were me and I didn't have the room, I'd make a bulge there to help the engine ... but you can't make a bulge in a wing spar easily. So, I guess it depends on where the connector is located as to whether or not the change is reasonable.


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## tomo pauk (Apr 10, 2020)

Reluctant Poster said:


> Continuing my harping.
> One of the improvements suggested by NACA in the attached paper replaces the pipe joining the two supercharger stages with a lower pressure drop design.
> As you can see the bends in the NACA design are much more gradual. According to the NACA tests, this simple change increased power by 10 HP. If two badly designed elbows can cost that much horsepower think of how much power was wasted in the Allison's convoluted intake manifold. I amazed that Allison still didn't understand flow at this late a stage.





fastmongrel said:


> That is a horrible tight bend on the standard duct I have seen ride on mowers with better intakes



Too bad that NACA found it fit to test and suggest improvements for the V-1710 in 1946.


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## jetcal1 (Apr 10, 2020)

Snowygrouch said:


> This is correct, the efficiency of the 1st stage is the most critical, and poor 1st stage performance is multiplied by each subsquent stage. They do not add, they multiply; its just that often the efficiecies are so low that from inspecting the total pressure ratio of a 2-stage compressor, its easy to think its added (e.g Merlin-61 total PR is about 6:1, but from the individual
> stages you might expect nearer 8 or 9 if multiplied - hence an easy mistake to make.).


Not just in superchargers either. Early low bypass engines like the (cough, cough!) TF30 and early F100's.


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## ThomasP (Apr 10, 2020)

Thanks for the info Reluctant Poster.


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## gjs238 (Apr 11, 2020)

Reluctant Poster said:


> Continuing my harping.
> One of the improvements suggested by NACA in the attached paper replaces the pipe joining the two supercharger stages with a lower pressure drop design.
> View attachment 576952
> View attachment 576951
> ...



Very interesting, I did not know that NACA was doing engine related research as well. Especially to the point of designing replacement parts.
I had assumed their work was limited to air-frame aerodynamics.
In this case, NACA is really pulling some of the load for Allison and/or Bell.

The document refers to the original elbow as "the standard Bell elbow."
Does that imply that Bell designed that elbow, not Allison?


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## swampyankee (Apr 11, 2020)

tomo pauk said:


> Too bad that NACA found it fit to test and suggest improvements for the V-1710 in 1946.



They hadn't been asked before then. Do note, however, that it's mentioned in the introduction that the USAAF and Allison had known of the problem before this.


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## Navalwarrior (Apr 11, 2020)

Navalwarrior said:


> Resp:
> The post WWII production F-82 used the Allison engine, as the Packard Merlin production license was about to expire. The F-82 had outstanding performance.


Don't:
Upon further research: "It was found that Allison-powered F-82 models (C models) demonstrated a lower top speed and poorer high-altitude performance than earlier Merlin-power versions." The C model used Allison V-1710-100 engines. Only 20 production F-82B models were made using the British designed Merlin engine.


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## swampyankee (Apr 11, 2020)

Navalwarrior said:


> Don't:
> Upon further research: "It was found that Allison-powered F-82 models (C models) demonstrated a lower top speed and poorer high-altitude performance than earlier Merlin-power versions." The C model used Allison V-1710-100 engines. Only 20 production F-82B models were made using the British designed Merlin engine.



From what I remember reading, the Allison-engined F-82s were about 20 mph, or about 5% slower, than the Merlin-engined aircraft.


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## tomo pauk (Apr 11, 2020)

V-1710 as installed on P-82 have had less power at altitude than the Merlins on P-82s.


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## Reluctant Poster (Apr 13, 2020)

Reluctant Poster said:


> The statement that Stellite does not contain Tungsten is not true, some varieties do, for example Stellite 6 contains 4-6% Tungsten. From what I have been able to ascertain early turbos used Stellite 6 for their blades , however the bulk of production used Stellite 21 which does not contain Tungsten and has the advantage of being able to be cast, which greatly simplified blade production. See the following link
> 
> Our Company History


As a matter of general interest, the attached is a history of strategic metals in WWII.

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## Reluctant Poster (Apr 13, 2020)

tomo pauk said:


> Too bad that NACA found it fit to test and suggest improvements for the V-1710 in 1946.


Too bad Allison couldn't design it properly in the first [place. Any company that relies on an outside entity to correct their mistakes will fail more often than not.
In any event the actual testing was done during the war.

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## tomo pauk (Apr 13, 2020)

Reluctant Poster said:


> Too bad Allison couldn't design it properly in the first [place. Any company that relies on an outside entity to correct their mistakes will fail more often than not.
> In any event the actual testing was done during the war.
> View attachment 577350



Thank you for the excerpt.
BTW, about the 1st sentence - RR was buying the bearings at Allison before ww2 because their bearings didn't work. They also used Farman-designed 2-speed drive for their superchargers.

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## Reluctant Poster (Apr 14, 2020)

tomo pauk said:


> Thank you for the excerpt.
> BTW - RR was buying the bearings at Allison before ww2 because their bearings didn't work. They also used Farman-designed 2-speed drive for their superchargers.



RR was never afraid to buy in components they felt outsiders could do better. They built their own carburetors (including the prototype Merlins) but realized the SU carb had an excellent method of controlling mixture vs altitude so they adopted that instead of their own.

Their bearings didn't work? Is there evidence showing that was the case? Rolls Royce saw a better way to do things and they did what successful organizations often do and took out a licence allowing them to produce a better product.
Here is an interesting discussion on RR Kestel and Merlin bearings in another forum
RR Kestrel Gilman Bearings

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## GregP (Apr 15, 2020)

Thanks for the link, Reluctant Poster. Nice info. In that link, one poster asks how Allison "renews" bearings. As it happens, I have some experience with Allison main bearings.

The standard crankshaft main journals are 3.7475 inches diameter with 0.0045 inches clearance between bearing and crankshaft. The only main bearing sizes are standard and 0.002 inches under, which means the bearing is 0.002 inches thicker than standard to allow for wear. The main bearing number stamped into the bearing faces the pilot in the #1 cylinder. The bearings are tapered and the standard bearings should have a 0.1865 inch taper.

The bearings themselves have 0.040 inches of Silver plated onto the steel and 0.002 inches of lead plated over the Silver. Copper is flashed on the outside of the shell half. The Allison V-1710 runs pressurized oil through the hollow crankshaft and the mains all have oil holes in them, so the mains get oiled while the engine is running. This is also why a "dry" engine should be pre-oiled before turning it over. If the engine has not been run in a while, it should be pre-oiled before turning the crankshaft over to save the main bearings. 

When the mains are changed, the old bearings can be collected and sent out to have them re-plated to new specifications. When they are installed, the bearings need to be fitted to the crankshaft. Most competent modern overhaulers use plastigage for clearance, and ALL new bearings need to be scraped the old way to get proper clearance. I know one overhauler who has an original Allison factory overhaul main bearing gauge that gets assembled into the mains to check for clearance. You lay it into the mains, assemble the case, and torque the mains to spec. When you do this, you should be able to turn the gauge by hand. If not, the bearings are too tight.

If you actually run one with mains that are too tight, the engine may seize within 20 - 30 minutes of flight or run time, and the cases, crankshaft, and rods will show signs of high heat by turning a bit blue-black. Joe Yancey found that in an Allison that had been installed into the P-38 "Brooklyn Bum" when he checked the engine after the aircraft came back to the U.S.A. from the U.K. If it had been run for longer than about 30 minutes, the engine would have seized.

It is important which way the crankshaft goes into the engine. When viewed from the accessory end, position the first crank throw at 12 o'clock. If the next throw points left, then it is left hand turning, viewed from the supercharger end. If the next throw points right then it is right-hand turning, viewed from the supercharger end. Serial numbers were originally stamped on supercharger end.

Left-hand and right-hand engines need different ignition harnesses. When you turn the crankshaft around (and install the idler gears and other-handed starter) for a left-hand engine, the inside cylinder wires have to be reversed in the harness. Another idler gear is also installed so the camshaft turns in the proper direction for the other-turning crankshaft. 

All Allisons should be right-hand turning except for the left-hand engine on a P-38 and the odd built-up left-hand engine if someone wants to put an Allison into an IL-2 or MiG-3. Paul Allen's IL-2 up in Seattle (Flying Heritage Museum) has a left-hand turn Allison by Joe Yancey in it, as does the MiG-3 flying occasionally in Moscow.

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## Piper106 (Apr 15, 2020)

Navalwarrior said:


> Don't:
> Upon further research: "It was found that Allison-powered F-82 models (C models) demonstrated a lower top speed and poorer high-altitude performance than earlier Merlin-power versions." The C model used Allison V-1710-100 engines. Only 20 production F-82B models were made using the British designed Merlin engine.



Per Dan Whitney in "Vee's for Victory"
XP-82 was to be powered with the Packard Merlin V-1650-23/25
XP-82A would have the Allison F32R/L V-1710-119/121 (Aircraft cancelled)
P-82B Allison offered the F33 R/L engine but the planes were produced with Merlin engines. 
P-82C and P-82D were P-82B aircraft modified to add radar. 
P-82E and P-82G originally to be Allison F36R/L V-1710-143/145 later changed to the Allison G6R/L also designated V-1710-143/145.

The F32 engine was two stage super charged with charged cooled after the engine stage (2 nd) supercharger, and Bendix SD-400 speed density (single point) injection. War emergency Rating was 2100 HP up to 4000 feet (grade 150 fuel required), 1720 HP at 20700 feet, and 1200 HP at 30000 feet. The G6 engines was however without the aftercooler but adding ADI (water) injection. The G6 was rated 2250 HP with water injection, and similar ratings at altitude as the F32..

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## tomo pauk (Apr 15, 2020)

Piper106 said:


> Per Dan Whitney in "Vee's for Victory"
> XP-82 was to be powered with the Packard Merlin V-1650-23/25
> XP-82A would have the Allison F32R/L V-1710-119/121 (Aircraft cancelled)
> P-82B Allison offered the F33 R/L engine but the planes were produced with Merlin engines.
> ...



I don't think that G6 have had similar ratings at altitude as the intercooled F32. We're probably looking at under 1000 HP at 30000 ft for the G6 - the similar V-1710-121 (F28) was making 930 HP at 3200 rpm at 30000 ft, and a bit less than 1700 HP at 17000 ft.


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## Piper106 (Apr 15, 2020)

tomo pauk said:


> I don't think that G6 have had similar ratings at altitude as the intercooled F32. We're probably looking at under 1000 HP at 30000 ft for the G6 - the similar V-1710-121 (F28) was making 930 HP at 3200 rpm at 30000 ft, and a bit less than 1700 HP at 17000 ft.



The F28 had the 9-1/2" engine stage impeller turned by 8.1:1 step up gears and the 7.23:1 gears in the auxiliary stage. The G6 had a 10-1/4" engine stage impeller turned by 7.48:1 gears with 8.03:1 auxiliary stage gears. For the G6 engine Whitney states (page 280): "The Military rating was set at 1250 HP and 30000 feet, a deviation from the intended 32500 feet. Allison then went on to achieve the intended altitude rating." Maybe the actual performance was lower, but that is what Whiney states based on a source letter from Allison to Air Materiel Command.

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## GregP (Apr 15, 2020)

Hi Tomo,

If you check Graham White’s Allied Aircraft Engines of World War II, the Allison V-1710-143 (G6R) had a rating at 1600 hp / 3200 rpm / Sea level, and 1250 HP / 3200 rpm / 30,000 feet. But I do not see an engine performance chart, so I couldn’t say what the critical altitude is or at what altitude it dropped off to what level.

Graham has about a page and quarter of Allison references, but hard data on the G-series seems to be a bit thin, probably due to being at the end of pistons / beginning of jets era.

I have the pleasure of having a friend who overhauls Allison engines, and he has a number of G-series engines available for overhaul as well as all the manuals to do it. He made a hybrid F/G engine for Reno a couple of years back and he put it into Graham Frew's Yak-3 for the races. Graham won Bronze, silver, and transferred into Gold. But the Hybrid engine had cooling problems due to the small size of the radiator in the Yak, and he finished with a standard 100-series Allison up front. Anyway, the hybrid engine definitely sounded WAY more powerful than a garden-variety Allison when Graham took off. Everyone noticed that part!

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## gjs238 (Apr 15, 2020)

Yes, but does the 2-stage Allison still have a lower parts count than the Merlin?


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## GregP (Apr 16, 2020)

Yes. The Auxiliary supercharger has very few parts. It is basically a casting with an impeller and some bearings and bolts and a driveshaft to turn it ... and not very many parts altogether.


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## wuzak (Apr 16, 2020)

GregP said:


> Yes. The Auxiliary supercharger has very few parts. It is basically a casting with an impeller and some bearings and bolts and a driveshaft to turn it ... and not very many parts altogether.



And a fluid coupling.


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## ThomasP (Apr 16, 2020)

Around 500 additional parts for the auxiliary stage supercharger and required power take-off unit. This does not include the carburetor and such since it would be needed for a single stage anyway. It also does not include the mounting accessories needed to attach the auxiliary supercharger to the airframe.


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## tomo pauk (Apr 16, 2020)

Piper106 said:


> The F28 had the 9-1/2" engine stage impeller turned by 8.1:1 step up gears and the 7.23:1 gears in the auxiliary stage. The G6 had a 10-1/4" engine stage impeller turned by 7.48:1 gears with 8.03:1 auxiliary stage gears. For the G6 engine Whitney states (page 280): "The Military rating was set at 1250 HP and 30000 feet, a deviation from the intended 32500 feet. Allison then went on to achieve the intended altitude rating." Maybe the actual performance was lower, but that is what Whiney states based on a source letter from Allison to Air Materiel Command.



You're right, I stand corrected.


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## GregP (Apr 16, 2020)

You are right, Wayne. I have helped assemble one for cleanup and paint, but it was on a stand by itself. We didn't connect it to an engine because nobody ordered one for purchase. The P-63 was going to run an E-series engine alone, and that is what we were working on. I only saw it because I was curious and asked about it.


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## MACHIA (Apr 30, 2020)

If the V1710-E27 would have been developed further and put into production it would have been the ultimate V12 engine rated at about 2,800 hp at the prop !
Came to late and the alloys available at the time in the turbo couldn’t stand up to the temperatures.


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## ronjon (Jul 8, 2022)

gjs238 said:


> Good question.
> Specifically, did the intrinsic design of the V-1710 preclude development of it's supercharger in the ways that the Merlin supercharger developed?
> Multi-speed, multi-stage, water cooling, etc.


Looking at the P-38’s high altitude performance, being properly turbo- (and presumably super-) charged proves the Allison could do what the Merlin could, and it probably had a lot more room to explore and exploit its potential. The Army told Allison to either stop or not start 2nd stage supercharger development as this was to be handled exclusively by the GE turbocharger, which didn’t work out for the P-39 because of packaging issues - there just wasn’t enough room for the ductwor, I suppose, due to the engine placement. I’m trying to research if the A-36 and P-40 were ever intended to be turbocharged, or were they meant to be low-altitude craft exclusively,and be fine w the 1st stage impeller.


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## Shortround6 (Jul 8, 2022)

Curtiss had at least a better idea of what it took to turbo charge an engine than most.
Not saying that they were 100% right, just that they had actually done it.






13 YP-37s. 

You need a lot of extra cubic feet of volume to fit the turbocharger, intercooler and duct work into the plane. 
The XP-39 was clear example of trying to stuff too much into too small a bag. 

North American may or may not have had drawings for a turbo charged Mustang/A-36 (although why you would turbocharge a dive bomber escapes me)
But we can pretty much be sure that it would NOT have fit into the existing fuselage out lines.


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## GregP (Jul 8, 2022)

wuzak said:


> In the turbocharged systems the turbo compensated for altitude, and that's all it did. And the integral supercharger was there to boost the intake charge above atmospheric (sea level) pressure. Which they did.
> 
> In engines without turbocharger the supercharger was to do both. It did this by being spun faster (different gearing). Unfortunately this meant that the engine couldn't take the boost the supercharger was capable of delivering at lower altitudes, so the intake had to be throttled to prevent overboosting.



A supercharger can be used to compensate for altitude, increase sea level horsepower, or both. If you elect to use it for both, some of the boost is used for the horsepower increase and the rest of the possible boost is used for altitude compensation. Naturally, if you use it for both, the critical altitude will be lower than if you used it all for altitude compensation alone. And, if you use all the supercharger boost for more horsepower, you can overboost, But even if you don't, there isn't any boost left for altitude compensation, and the horsepower just falls off with altitude normally.

A turbocharger is no different from a supercharger; both are compressors. In fact, many use the exact same compressor design. It's just that one is driven by the engine (supercharger) and the other is driven by exhaust gases (turbocharger). Likewise, you can use the boost any way the designer wants to use it ... for altitude compensation alone (call turbo-normalizing), for more horsepower alone, or for both. Again, if you use it for both, then there is less boost available than if you turbo-normalize it.

Let's say you have 10 psi of boost. If you turbo-normalize, then you can make sea level horsepower way up high. But if you use 4 psi of it to increase horsepower, that only leaves 6 psi of boost for altitude compensation. It won't go as high as it will with all 10 psi of boost used for altitude compensation, before running out of boost and losing power with altitude gained.

Pretty simple qualitatively. No so simple quantitatively, as the guys at Bell Aircraft found out for themselves.


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## Reluctant Poster (Jul 8, 2022)

ronjon said:


> Looking at the P-38’s high altitude performance, being properly turbo- (and presumably super-) charged proves the Allison could do what the Merlin could, and it probably had a lot more room to explore and exploit its potential. The Army told Allison to either stop or not start 2nd stage supercharger development as this was to be handled exclusively by the GE turbocharger, which didn’t work out for the P-39 because of packaging issues - there just wasn’t enough room for the ductwor, I suppose, due to the engine placement. I’m trying to research if the A-36 and P-40 were ever intended to be turbocharged, or were they meant to be low-altitude craft exclusively,and be fine w the 1st stage impeller.


The first statement doesn’t stand up to close scrutiny, no Allison ever matched the performance of a 100 series Merlin. There is no evidence that the Army stopped Allison from working on 2 stage supercharging. Allison were building test models in 1942. The problem is that Allison didn’t think about actually fittingly it into existing aircraft. This is in stark constrast to Rolls Royce who designed a very compact 2 stage arrangement for the Merlin and extensively redesigned the Griffon to allow it to fit into Merlin engined aircraft.

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## Reluctant Poster (Jul 8, 2022)

tomo pauk said:


> Too bad that NACA found it fit to test and suggest improvements for the V-1710 in 1946.


Actually, NACA was working on the V-1710 in 1942.

From the NASA website:

SP-4306 Engines and Innovation: Lewis Laboratory and American Propulsion Technology

"Ben Pinkel, one of the NACA's leading propulsion experts, directed the NACA's research on the exhaust gas turbine, another name for the turbo supercharger. Pinkel had come to the NACA in 1931 from the University of Pennsylvania with a degree in electrical engineering. In 1938, when Pinkel was appointed head of the Engine Analysis Section, it had a staff of three. By 1942, Pinkel's division had expanded to over 150 people. Although facilities were lacking at Langley, as soon as the Cleveland Laboratory was ready, Pinkel's Thermodynamics Division launched a strong program to improve exhaust gas turbines. In a talk to the staff, all of whom, he humorously remarked, demonstrated the principle of "heat in motion," Pinkel illuminated the importance of their work to the war effort. Adding a turbo supercharger to the engine of the B-17 "Flying Fortress," once thought obsolete, had made it a high-speed, high-altitude airplane. "This caused considerable excitement at the time because there wasn't a pursuit ship in the air force that could keep up with it."*17​* Testing in 1939 by Ben Pinkel, Richard L. Turner, and Fred Voss confirmed the predictions of a German, Hermann Oestrich, who suggested that the horsepower of an engine could be increased by the redesign of the nozzles of the airplane's tailpipes. The Power Plants Division became an advocate of "exhaust stacks" added to the tailpipes of aircraft. Once they were adopted by the aircraft manufacturers, they led to dramatic increases in performance fighter planes, including the North American P-51 and the British Spitfire.*1"​*

"Laboratory staff was less enthusiastic about its work on the Allison liquid-cooled engine. Although many of their research programs were simply a carryover of work begun at Langley, Army Research Authorization E-1 to improve the power output of the Allison-1710 engine was different. Issued in October 1942, it was the laboratory's first new research project. Hap Arnold, Chief of the Army Air Forces, counted on the Cleveland laboratory to assist in the redesign of the Allison supercharger and intercooler. Three engines were sent to the laboratory. Schey's division investigated the supercharger to give it better performance. Rothrock's division explored its limitations in terms of knock; Pinkel's division took on the problem of cooling. Moore's Engine Components Division improved the distribution of fuel and air in the carburetor.

The Allison engine, however, never met the expectations of the Army Air Forces. The Cleveland Laboratory's work on the Allison engine increased its horsepower through the use of water injection and supercharging. However, from Ben Pinkel's point of view, this work was a "tremendous waste of effort" because of the basic flaws in the engine's design. Only after the Army substituted the British Merlin engine, in the P-51 Mustang did the United States finally have a fighter for high-altitude flight.*"​*

The full article:
ch2

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## tomo pauk (Jul 9, 2022)

Reluctant Poster said:


> Actually, NACA was working on the V-1710 in 1942.
> 
> From the NASA website:
> 
> SP-4306 Engines and Innovation: Lewis Laboratory and American Propulsion Technology



Cool that they did. 

Unfortunately, the article contains too much of questionable statements, some of them misleading:
- _Adding a turbo supercharger to the engine of the B-17 "Flying Fortress," once thought obsolete, had made it a high-speed, high-altitude airplane. "This caused considerable excitement at the time because there wasn't a pursuit ship in the air force that could keep up with it."
_
Once thought obsolete??? Each B-17 have had 4 engines, thus will need 4 turboes per ship. It was Boeing and GE that were instrumental in a B-17 having turbocharged engines, not the PP Division.

-_The Power Plants Division became an advocate of "exhaust stacks" added to the tailpipes of aircraft. Once they were adopted by the aircraft manufacturers, they led to dramatic increases in performance fighter planes, including the North American P-51 and the British Spitfire._*1"​*

Leading to a reader to conclude that Spitire received a dramatic performance increase due to the advice on exhaust stacks received by PPD.

_- Three engines were sent to the laboratory. Schey's division investigated the supercharger to give it better performance. Rothrock's division explored its limitations in terms of knock; Pinkel's division took on the problem of cooling. Moore's Engine Components Division improved the distribution of fuel and air in the carburetor._

Fine, although one would love to see the test reports from 1943.

- _The Allison engine, however, never met the expectations of the Army Air Forces._

It certailny met them in 1940, when it enabled a 30+ mph jump in pursuit speed over the then-current pursuits. Also in the P-38. For engines that never met the AAF expectations, we can take a look at a few of the hy-per engines sucking the resources the V-1710 could've used.

- _The Cleveland Laboratory's work on the Allison engine increased its horsepower through the use of water injection and supercharging. However, from Ben Pinkel's point of view, this work was a "tremendous waste of effort" because of the basic flaws in the engine's design._

Not listing the supposed basic flaws is a red flag. 

- _Only after the Army substituted the British Merlin engine, in the P-51 Mustang did the United States finally have a fighter for high-altitude flight._*"​*

Seems like the P-47 never existed.​

tl;dr: When an institution writes their own history, it will be not the 1st nor the last time they migh twist the facts in order for themselves to look good.​

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## Shortround6 (Jul 9, 2022)

Hmmm, not a lot mention about the Continental 1430 which was actually the armies fair haired boy in disguise.
They didn't give up on it until 1944 while trying to beat the Allison engine. 

and I have no idea of where this came from in Wiki, but the entry on the XI-1430 sounds like they were written by USAAC press release hacks. 

_Continental built the first I-1430 engine in 1938 and successfully tested it in 1939.[1]​ At the time it was an extremely competitive design, offering at least 1,300 hp (970 kW) from a 23-liter displacement; the contemporary Rolls-Royce Merlin offered about 1,000 hp (700 kW) from 27 L displacement,_

and

_In 1944 it was also tested in the McDonnell XP-67.[1]​

Interest in the design had largely disappeared by then; piston engines with the same power or greater ratings were widely available, the Merlin for example had improved tremendously and was offering at least 1,500 hp (1,120 kW), and the military and aircraft builders were already starting to focus on jet engines._

the 1430 managed to set fire to only two planes it was ever installed in. They built 23 of them and built it in or planed to build 13 different versions?

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## drgondog (Jul 9, 2022)

Shortround6 said:


> Hmmm, not a lot mention about the Continental 1430 which was actually the armies fair haired boy in disguise.
> They didn't give up on it until 1944 while trying to beat the Allison engine.
> 
> and I have no idea of where this came from in Wiki, but the entry on the XI-1430 sounds like they were written by USAAC press release hacks.
> ...


Good points on 1430.In 1941 NAA rejected it because of cooling issues primarily, then like the auxilary 2S it was also too long.


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## Reluctant Poster (Jul 9, 2022)

tomo pauk said:


> Cool that they did.
> 
> Unfortunately, the article contains too much of questionable statements, some of them misleading:
> - _Adding a turbo supercharger to the engine of the B-17 "Flying Fortress," once thought obsolete, had made it a high-speed, high-altitude airplane. "This caused considerable excitement at the time because there wasn't a pursuit ship in the air force that could keep up with it."_
> ...


Agreed. The point that I was making is that NACA was working on the V-1710 through most of the war.

However, when I read your first quote, I don't think they are actually taking credit for turbocharging the B-17. It certainly wasn't considered to be obsolete.
Here is a more nuanced description of NACA involvement from NASA - WWII & NACA: US Aviation Research Helped Speed Victory

"Engine research did not receive very much public attention. One project NACA engineers often high-lighted was their work on the engines for the Boeing B-17 Flying Fortress. While testing the early B-17 prototypes, the Army had discovered that adding a turbo-supercharger would greatly improve the altitude and speed of the bomber. The Army ordered future B-17s be equipped with turbo-superchargers. Supercharger technology was not very well developed and Wright Aeronautical, makers of the R-1820 Cyclone engines used on the B-17, struggled with the requirements. This was precisely the kind of problem the engine lab was intended to work on. Eventually, the turbo-supercharger problems were resolved and the B-17, a true high-altitude, high speed bomber, went on to become one of the military's most successful bombers. The turbosupercharger was also used with great success in the Boeing B-29 Superfortress. The Wright R-3350 Duplex Cyclone that powered the B-29 also underwent extensive testing in the NACA's new Altitude Wind Tunnel at the engine lab."

To be fair to NACA they did a lot of research into superchargers and turbochargers in the inter war period. I have attached a NACA paper as an example.

The second quote certainly does try to take credit for the improved Spitfire exhaust stacks. NACA did test exhausts on a Spitfire V, but I am sure that Rolls Royce had done their own research into Merlin exhaust systems. I have attached a copy of the report


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## tomo pauk (Jul 9, 2022)

Reluctant Poster said:


> Agreed. The point that I was making is that NACA was working on the V-1710 through most of the war.



They probably did. Again, unfortunately, the effects of whatever the improvements they whipped up for the V-1710 seem to be very, very elusive until too late. If someone can correct me on this I'd be very grateful.



Reluctant Poster said:


> However, when I read your first quote, I don't think they are actually taking credit for turbocharging the B-17. It certainly wasn't considered to be obsolete.



Agreed on the 2nd sentence there, too bad PPD disagrees (disagreed).



Reluctant Poster said:


> Here is a more nuanced description of NACA involvement from NASA - WWII & NACA: US Aviation Research Helped Speed Victory
> 
> "Engine research did not receive very much public attention. One project NACA engineers often high-lighted was their work on the engines for the Boeing B-17 Flying Fortress. While testing the early B-17 prototypes, the Army had discovered that adding a turbo-supercharger would greatly improve the altitude and speed of the bomber. The Army ordered future B-17s be equipped with turbo-superchargers.



Army didn't 'discovered' that adding a turbo would greatly improve things while testing the early B-17 prototypes, they knew it will, since they were championing the research wrt. turbocharging through 1930s, and were using aircraft with turboed engine(s) in 1930s. 
Engine on the B-17 is one thing, addition of turbo is another thing.



Reluctant Poster said:


> Supercharger technology was not very well developed and Wright Aeronautical, makers of the R-1820 Cyclone engines used on the B-17, struggled with the requirements. This was precisely the kind of problem the engine lab was intended to work on. Eventually, the turbo-supercharger problems were resolved and the B-17, a true high-altitude, high speed bomber, went on to become one of the military's most successful bombers. The turbosupercharger was also used with great success in the Boeing B-29 Superfortress. The Wright R-3350 Duplex Cyclone that powered the B-29 also underwent extensive testing in the NACA's new Altitude Wind Tunnel at the engine lab."



One is left to question of just how the under-staffed PPD was able to solve the addition of turbochargers for B-17s already in 1939. Also - was the solution of supercharger problems just due to the work of PPD, or someone else sould be mentioned, perhaps the company making B-17s, and/or company making turboes?



Reluctant Poster said:


> To be fair to NACA they did a lot of research into superchargers and turbochargers in the inter war period. I have attached a NACA paper as an example.



They certainly did. 
I've read a lot of NACA reports, just like a lot of other enthusiasts. Problem is when someone muddles the water for no particular reason, bar to paint the (any) institution in the best light possible. Nobody was twisting the arms of the writer to claim the things he claimed in the article quoted before. 
A writer has test report(s) that prove that V-1710 was with 'basic flaws' making any improvement a waste of resources? Point out to the test reports, or don't mention that at all if there is no proof.



Reluctant Poster said:


> The second quote certainly does try to take credit for the improved Spitfire exhaust stacks. NACA did test exhausts on a Spitfire V, but I am sure that Rolls Royce had done their own research into Merlin exhaust systems. I have attached a copy of the report



Thank you.
I guess both you any I know that a major performance jump for the Spitfires and Mustangs came from installation of ever-better engines after all.


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## GregP (Jul 9, 2022)

Reluctant Poster said:


> The first statement doesn’t stand up to close scrutiny, no Allison ever matched the performance of a 100 series Merlin. There is no evidence that the Army stopped Allison from working on 2 stage supercharging. Allison were building test models in 1942. The problem is that Allison didn’t think about actually fittingly it into existing aircraft. This is in stark constrast to Rolls Royce who designed a very compact 2 stage arrangement for the Merlin and extensively redesigned the Griffon to allow it to fit into Merlin engined aircraft.



Early Allisons were every bit the horsepower of early Merlins. Both were just over 1,000 hp. The early nose case wasn't the best design but, by the time the E and F series Allison came out, they were fine. It took Sir Stanley Hooker's efforts to make the 60-series and later Merlins with his compact 2-stage supercharger. The late Allisons were pretty good at 1,600 hp WER. . The aux-stage units made very good HP.

There is PLENTY of evidence the government rejected Allison's desire to develop a 2-stage unit. All you have to do is go look for it. The auxiliary-stage they came up with was funded in-house.

Allison produced what the government ordered. Had the government funded development, Allison could have done it, and that is what you get when your engine design is funded and owned by the government. Initial development was funded by and owned by the U.S. Navy as a dirigible engine. Later developments came about with Navy and Air Corps funding. Allison didn't have Rolls-Royce's pocketbooks and most of the early days were consumed with trying to build enough infrastructure to satisfy the orders coming in rather than performance development.

The Merlin was and IS a great engine, especially later (60-series and later), if you needed to fly high. But a properly worked out turbo system was as good as a 2-stage supercharger. A Lockheed P-387L, with a good turbo system had a service ceiling of 44,000 feet. The last Merlin Spitfire, the Mk IX, had a service ceiling of 42,500 feet. The P-38L was also faster than the Spitfire IX. So, saying the Allisons never matched up isn't exactly looking at all the facts.

Personally, I think the Merlin was better suited to the ETO's higher-altitude operations because turbo systems were complex by comparison to supercharger systems and required special metals to handle the heat. Allison development generally lagged Merlin development due to Rolls-Royce being able to do what they pleased while Allison was dependent on government funding for any development. That being said, an Allison held a tune longer, had a longer TBO in general, and was more rugged, but the Merlin was a great performer and served with distinction. The TBOs were set not by how the engine ran or by age, but by the desire for 99% of all engine blocks being sent in for rebuild to actually BE rebuildable.

I'd say the Merlin was gem but there was nothing wrong with an Allison, assuming you were fighting in the Allison's altitude band, after the few issue were worked out. That was late 1942 early 1943. The issue came if you needed to fight up high. In that case, you needed the turbo or the auxiliary-stage supercharger, which the P-39 and P-40 didn't get. So, you were left with the P-38 as your choice. The P-63 was very good in the mid 20,000 foot area, but didn't have the range to be generally useful, so it never got procured by the USAAF. The Soviets loved it since they had use for a shorter-range interceptor.

Look at the top 10 U.S. aces. Collectively they shot down 323.83 enemy aircraft. About 8 were in P-40s; 27 in P-51s; 34 in F6Fs; 45 in F4Us; 50 in F4Fs; 55 in P-47s; and 105 in P-38s. You might see that the P-38 (Allison power) shot down about twice the percent of any of the other top 10 ace mounts. Perhaps dismissing the Allison is disingenuous?

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## FLYBOYJ (Jul 9, 2022)

> There is no evidence that the Army stopped Allison from working on 2 stage supercharging. Allison were building test models in 1942. The problem is that Allison didn't think about actually fittingly it into existing aircraft.





> GregP said:
> 
> 
> > Allison produced what the government ordered. *Had the government funded development, Allison could have done it*, and that is what you get when your engine design is funded and owned by the government.



Greg hits this nail on the head and many folks don't realize, forget or simply refuse to understand that *manufacturers very rarely go into projects unfunded and/or unsolicited!!!!*

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## pbehn (Jul 9, 2022)

FLYBOYJ said:


> Greg hits this nail on the head and many folks don't realize, forget or simply refuse to understand that *manufacturers very rarely go into projects unfunded and/or unsolicited!!!!*


The two stage Merlin started as a government request for a high altitude Wellington bomber. RR may have had ideas about what could be done and discussed them but the finance for such a project comes from others, usually a government.

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## FLYBOYJ (Jul 9, 2022)

pbehn said:


> The two stage Merlin started as a government request for a high altitude Wellington bomber. RR may have had ideas about what could be done and discussed them but the finance for such a project comes from others, usually a government.


Exactly.

We've discussed this before - there have private ventures that were eventually bought by "a government," but those are more the exception than the rule. "No one does something for nothing."


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## Shortround6 (Jul 9, 2022)

FLYBOYJ said:


> "No one does something for nothing."




Allison especially and for very good reason. 

In the spring/summer of 1939 the government owed Allison over 900,000 dollars for work already done. 

It order to accept overseas orders Allison had to "forgive" (write off) the dept. 

If Allison had not gotten the contract for the P-40 engines in April of 1939 there is a good chance GM would have shut down the engine division and kept the bearing division. 
GM had loaned Allison about 500,000 dollars to keep the engine division open. 

So Allison had already done a lot of something for nothing and had been burned badly by the government. 
Allison had looked at two stage supercharging in 1938-39 but already had a number of projects in the works.

Now we get a bunch of people saying Allison should have funded two stage supercharger development themselves. 
In 1939 Allison had 25 people working in the engineering dept. That includes the two men who ran the blueprint machine, the number of actual engineers was some want less. 
Allison was trying to design the P-39 driveshaft and remote gearbox.
Allison was trying to finish off the pusher props, extension shafts on the Airacuda. 
Allison was trying to come up with turbo version for the YP-38s. 
Allison was working on the V-3420 24 cylinder engine.
Allison was trying to figure out how to mass produce the V-1710 engine, from 1931 through the end of 1939 Allison had built 78 engines. 
The engineering staff was responsible for laying out the new production facilities, ordering the machine tools, designing the jigs and fixtures and designing any improvements, modifications.

Allison to government "Oh, you want a two stage supercharger in addition to all that? And you want us to pay for it until you can slip it into a future budget (but not this year?) 
Ok, yeah, we will get right on that!!!!!" Don't hold your breath whispered in low tone.

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## FLYBOYJ (Jul 9, 2022)

There are times where contract administrators will negotiate themselves into situations like this with no consideration to economics or to the rank and file designing and building this stuff. These contracts today are known as "as risk" contracts, "assuming" that the government will eventually open the checkbook. There's a lot of clauses in today's world when at risk contracts are paid, not only the "loaned money" is paid, but it is paid with interest.


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## GregP (Jul 10, 2022)

FLYBOYJ said:


> Greg hits this nail on the head and many folks don't realize, forget or simply refuse to understand that *manufacturers very rarely go into projects unfunded and/or unsolicited!!!!*



I am reminded that Lady Houston gave generously to British aviation. In 1931, she donated £100,000 to Supermarine, allowing them to win the Schneider Trophy in that year.[3]​ The Royal Air Force's entry for the 1931 race for the trophy was hindered by political opposition. On 15 January 1931, the Air Ministry refused a last-minute request by the Royal Aero Club for funds for an entry. With the economic crisis the Cabinet vetoed RAF involvement and Government funding in a sporting event. Marshal of the Royal Air Force, Sir Hugh Trenchard held the view that there was no advantage as aircraft development would continue whether or not the UK competed.[8]​ The Ministry forbade the use of the aircraft that competed in the 1929 race; forbade RAF pilots of the High Speed Flight who were trained to fly these seaplanes, to take part; and said that it would not police the race course in 1931 in the busy shipping lanes in the Solent. The Royal Aero Club sent a statement to the Cabinet on 22 January 1931, offering to raise £100,000, if the Government would rescind the Air Ministry's decrees on planes, pilots and policing.

Many newspapers backing the opposition Conservative Party wanted to put pressure on Ramsay MacDonald's National government. One newspaper sent a telegram to MacDonald stating that, "To prevent the socialist government from being spoilsports, Lady Houston will be responsible for all extra expenses beyond what Sir Philip Sassoon[9]​ (President of the Royal Aero Club) says can be found, so that Great Britain can take part in the race for the Schneider trophy." The gift gave Lady Houston an opportunity to attack the Labour government, with the declaration "Every true Briton would rather sell his last shirt than admit that England could not afford to defend herself."

So, without Lady Houston's funding, we may never had had either the Merlin OR the Spitfire as we knew and KNOW them. While she was a boon to British aviation, Rolls-Royce, and Supermarine, Allison never had any such private OR public funding funding supplied by anyone.

If you use an inflation and currency calculator you can find that £100,000 in 1930 equates to $8,770,000 in 2020. Not exactly chicken feed, is it?

Now, I could be overstating it, but that's a pretty decent shot to a company in development of a privately-funded aviation engine! 

Wow! It seems to me they did a very good job with Lady Houston's contribution in coming up with the R engine that turned into the Merlin engine. With that in mind, I'm not too ashamed of the Allison that got developed by a whole lot less funding and people who, if they were not exactly in a driving hurry, at least were not about to get bombed by the Luftwaffe. That certainly takes a bit of urgency out of the task. 

I'm impressed with what Allison came up with in their considerably less well-funded development but, if pressed, would STILL take a Spitfire into battle in 1942 before I'd choose either a single-stage P-39 or P-40. Truth be told, I'd likely wait until the P-38J-25 that had hydraulic ailerons or the P-38L before choosing to fight in it.

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## buffnut453 (Jul 10, 2022)

GregP said:


> So, without Lady Houston's funding, we may never had had either the Merlin OR the Spitfire as we knew and KNOW them. While she was a boon to British aviation, Rolls-Royce, and Supermarine, Allison never had any such private OR public funding funding supplied by anyone.



Greg, I love you brother...but there's so much that's wrong or misleading about this statement that it's really hard to know where to begin.

Yes, Lady Houston provided 100K to Supermarine (not Rolls Royce - that point is key) in 1931 for the Schneider Trophy race later that year. However, the impact of that funding on Spitfire or Merlin development was exactly ZERO. There was a lot of emotion at the time, and the outright winning of the Schneider Trophy was a tremendous boon to Britain at a time of considerable financial instability. However, in-year funding simply didn't allow enough time to develop anything truly new for the 1931 race. Lady Houston's investment did not change the direction of aircraft technology development in the UK. 

Let's look at the airframe first. R.J. Mitchell took the Supermarine S6 that had won the 1929 race and tweaked the floats, lengthening them by 3ft, reducing their frontal area, and incorporating additional radiator cooling for the engine as part of the float design. The two original S6 racers from 1929 were updated with the different floats and designated S6A and 2 new airframes, which also integrated a more powerful Rolls Royce R engine, were designated S6B. None of that had any impact on design of the Spitfire. Apart from the floats, the rest of the airframe was pretty much unchanged from the 1929 Supermarine S6. As to evolution of the S6 into the Spitfire, the two airframes have nothing in common except the designer. The S6 still used wire bracing for the wings, tailplane and floats, whereas the Spitfire was of monocoque construction, which was an entirely different design philosophy.

As for the engine, the Rolls Royce R was developed from the Buzzard which was an up-scaled Kestrel, all of which were being worked on pretty much at the same time in the period 1927-1929. All these engines were funded by the British Government and they all used superchargers. The R powered the Supermarine S6 in the 1929 race and was further developed for the 1931 race, although it was still under UK Government funding (in April 1931, one of the R engines undertook an Air Ministry acceptance test which wouldn't be done if it was privately funded). None of these engines had any commonality with the Merlin which was privately funded (its original designation was PV12, PV standing for Private Venture) because Rolls Royce recognized that a larger engine would be needed to generate future power requirements.

Rolls Royce kicked off the PV12 in 1933 and started receiving Government funding in 1935 when it was decided that the PV12 should be the basis for requirements that ultimately led to the Spitfire and Hurricane. This was not some massive program initiated by the deep-pocketed Rolls Royce. Only 2 PV12 engines were built, passing bench testing in July 1934 with a first flight in February 1935. It was at this time that UK Government funding kicked in to evolve the PV12 into the the Merlin B. Again only 2 Merlin Bs were built, and they introduced glycol cooling (the PV12 employed evaporative cooling that had been much in vogue in the early 1930s but was operationally useless for combat aircraft). The Merlin C, E and F were developments of the B, with the latter being designated Merlin MkI as the first production example in 1936.

Ultimately, Trenchard was bang on the money. The RAF's participation in the 1931 Schneider Trophy race had no impact on aircraft technology development because all the main progress for the Schneider Trophy had already been made in 1929. In terms of engine development, the Kestrel and larger Buzzard were already well underway. Yes, the R engine provided some lessons on maintaining high performance but the fundamentals were already there thanks to the Kestrel, as was a team of experienced engine designers and developers to further evolve the technology.

All this whining about Allison not getting private or public funding reminds me of the tortuous conversations we've had about whether the Spitfire could have been turned into a decent long-range escort fighter. The pro lobby (typically Brits) contend that it was feasible. The anti lobby (typically Americans) often float the rhetorical question "If it was feasible, why wasn't it done?" closely followed with "couldda-wouldda-shouldda" for any attempt to argue the case. The simple reason the Spitfire wasn't developed into a long-range escort fighter was because the RAF had no need of that mission and so development of the airframe into that role didn't meet the funding threshold. We can say EXACTLY the same about development of the Allison engine.

The Allison was and is a great engine and, yes. it could have evolved into an effective competitor to the Merlin in the late 1930s if the US Government had invested in superchargers...but they didn't, and to do so would require different US Government funding decisions stretching back a decade prior. The US Government didn't see supercharger development as a priority and so didn't fund it. The British Government did invest, and the result was a solid base of experience within Rolls Royce that ultimately led to the PV12. Anything else is "couldda-wouldda-shouldda", I'm afraid.

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## SaparotRob (Jul 10, 2022)

Just how difficult would it have been to build a short range Mustang?

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## Shortround6 (Jul 10, 2022)

SaparotRob said:


> Just how difficult would it have been to build a short range Mustang?


Easy, make the ground crew refuel the plane using 5 gallon jerry cans.

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## GregP (Jul 10, 2022)

buffnut453 said:


> Greg, I love you brother...but there's so much that's wrong or misleading about this statement that it's really hard to know where to begin.
> 
> Yes, Lady Houston provided 100K to Supermarine (not Rolls Royce - that point is key) in 1931 for the Schneider Trophy race later that year. However, the impact of that funding on Spitfire or Merlin development was exactly ZERO. There was a lot of emotion at the time, and the outright winning of the Schneider Trophy was a tremendous boon to Britain at a time of considerable financial instability. However, in-year funding simply didn't allow enough time to develop anything truly new for the 1931 race. Lady Houston's investment did not change the direction of aircraft technology development in the UK.
> 
> ...



The impact was zero? You have to be kidding.

The S.4, S.5, and S.6 led directly to the Spitfire AND the Merlin, which was a direct development of the S.6 engine.

At least, that's what my books on engines and the Spitfire say. 

The S.4 and S.5 were decent, even good, but the lack of the S.6, had it never been raced, would have affected the Spitfire and the Merlin development. Throwing the equivalent of $8.7M at the effort didn't help immensely? Are you serious?

Well, I love you back, but will have to respectfully disagree with that. 

Thing is, either way, the Spitfire and Merlin were winners together. They were great.

That doesn't detract from the fact that the Allison made a huge contribution to U.S. aviation in WWII, regardless of any nay-sayers claiming it didn't measure up. When it counted, the Allison was there and powered the mount of our two top aces. I'd say that qualifies as "good enough" at minimum.


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## buffnut453 (Jul 10, 2022)

GregP said:


> The impact was zero? You have to be kidding.
> 
> The S.4, S.5, and S.6 led directly to the Spitfire AND the Merlin, which was a direct development of the S.6 engine.
> 
> ...



But there would still have been a Supermarine S6 even if the Brits had pulled out of the 1931 Schneider event. The S6 won the 1929 event and was tweaked into the S6A and S6B for the 1931 race. So my argument stands...the 1931 Schneider Trophy race had zero impact on British aeronautical progress. 

The Merlin was an amalgam of lessons learned with the Kestrel, Buzzard and the R (and there were over 4,000 Kestrels built). It's ludicrous to suggest that the Merlin was driven by the R when it patently wasn't. As I noted, some lessons were learned from the high-performance R engine but that wasn't the be-all and end-all. Lessons were also learned developing the larger Buzzard from the Kestrel, and from mass-producing the latter...and all were fitted with superchargers.

I can't disagree that the Allison made a huge contribution. However, it was at least 2-3 years behind the Merlin in performance...which means it couldn't have met the role the Merlin fulfilled in the period 1939-1942. After 1942, sure, the Allison is comparable but not before.


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## drgondog (Jul 10, 2022)

SaparotRob said:


> Just how difficult would it have been to build a short range Mustang?


The P-509 would have range slightly greater than P-39/P-40 range in 1940-41 but projected faster and better climb than NA-73 as it was refined between RAF and NAA. P-09 proposed at 130 gal, then 150 for NA-73X , then 170 for Mustang I production, then 180 for Mustang IA and P-51, then 180 for P-51A

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## Shortround6 (Jul 10, 2022)

buffnut453 said:


> As for the engine, the Rolls Royce R was developed from the Buzzard which was an up-scaled Kestrel, all of which were being worked on pretty much at the same time in the period 1927-1929. All these engines were funded by the British Government and they *all used superchargers.* The R powered the Supermarine S6 in the 1929 race and was further developed for the 1931 race, although it was still under UK Government funding (in April 1931, one of the R engines undertook an Air Ministry acceptance test which wouldn't be done if it was privately funded). None of these engines had any commonality with the Merlin which was privately funded (its original designation was PV12, PV standing for Private Venture) because* Rolls Royce recognized that a larger engine would be needed* to generate future power requirements.


A few corrections.
The Kestrels did not start with superchargers, in service, although designed for them. They were soon added but both supercharged and non-supercharged Kestrels were offered for quite some time during the same period. The Kestrel was even offered with two different compression ratios in the unsupercharged form depending on fuel and intended use of the engine. Instructions for the "F" engine said that full throttle was not to be used below 2,000ft in the moderate compression engine, below 3,000ft in the high compression engine or below 11,500ft with the supercharged engine. Later supercharged Kestrels offered different compression ratios and different supercharger gears. 

The Buzzard was always supercharged although both compression ratio and boost were limited. Sales were also limited. Most airframe makers couldn't quite figure out what to do with it. 
The type "R" was a considerably beefed up/modified buzzard and this is where the benefit of the racing program came in. Partially because it got RR into rapid problem solving and modification. The type "R" was not a group of slightly modified engines but a succession of modifications, some of which were major. In the series was the first use by RR of the sodium cooled exhaust valve. 

What lead to the Merlin was the need for an in-between engine between the Kestrel and the Buzzard/"R". RR needed a large engine than the Kestrel but the airframe makers weren't quite ready for the Buzzard/"R"/ Griffon (all three used the same bore x stroke=displacement). With better fuels and the knowledge from the "R" racing program RR could build as smaller engine than the Buzzard in size while making nearly as much power. Granted the Merlin went through several design changes before they steadied down. 
RR placed Buzzard/Griffon on hold in 1933. This derated R engine was run in 1933 but not flown in aircraft. In 1938-39 they started back up again with the reconfigured/smaller on the outside Griffon II engine first run in Nov 1939. This was the engine the RN was looking at in it's 1940-41 aircraft. 

The racing program was useful to RR but it wasn't as direct connection that some might think. The 1931 racers could use up to 17.5lbs of boost and the record setting flight may have used even more. It used a different fuel blend than the trophy race. RR may have learned a lot about supercharge design compared to other companies at this time. 

Supercharger design was not stagnant but with low octane fuel in service engines a lot of potential problems did not show up.

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## Shortround6 (Jul 10, 2022)

GregP said:


> Merlin, which was a direct development of the S.6 engine.


The R was a development of the Buzzard, kind of/sort of. 
Rowledge added two additional cylinder hold down saddle studs per cylinder for example to help keep the engine together at higher power.
The moving parts owed a lot to the Buzzard the engine structure was designed for much higher loads. 

Since the Merlin used a smaller bore and stroke and thus smaller valves (5.4 in bore vs 6 in bore). it is a bit hard to see the connection. 
R engines may have used different connecting rods. Some, at least, used master and slave rods and not the fork and blade rods. 

I am sure that Rowledge used a lot of knowledge used in the development of the R when working of the Merlin but to claim the Merin was a direct development of the engine/s used in the S.6 aircraft is stretching things, makes for a good story though  

As outlined above, the Griffon was a closer descendent of the R than the Merlin was.

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## SaparotRob (Jul 10, 2022)

drgondog said:


> The P-509 would have range slightly greater than P-39/P-40 range in 1940-41 but projected faster and better climb than NA-73 as it was refined between RAF and NAA. P-09 proposed at 130 gal, then 150 for NA-73X , then 170 for Mustang I production, then 180 for Mustang IA and P-51, then 180 for P-51A


Wrong! Have Bell build it.

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## special ed (Jul 10, 2022)

So, my question is, how did Supermarine get their R engines for 1931? Did RR, out of the goodness of their heart give the enginese to Supermarine or did they buy them from RR with Lady Houston's donation? It would seem that there is more to the story. Surely the Air Ministry would try to preserve their pride by refusing RR to allow the engines to Supermarine. Possibly Lady Houston had influence in high places.


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## GregP (Jul 10, 2022)

special ed said:


> So, my question is, how did Supermarine get their R engines for 1931? Did RR, out of the goodness of their heart give the enginese to Supermarine or did they buy them from RR with Lady Houston's donation? It would seem that there is more to the story. Surely the Air Ministry would try to preserve their pride by refusing RR to allow the engines to Supermarine. Possibly Lady Houston had influence in high places.



I'm sure there was more to the story.

I'm also fairly sure that the whole story may never be known.

But, if you take a talented group of aircraft and engine designers and add $8.7M to their war chest, I'm pretty sure you get much better results from their efforts than would have been achieved without the addition of said extra funds. If nothing else, they at LEAST get to try a few things they would not have been able to try without the extra money.

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## buffnut453 (Jul 10, 2022)

special ed said:


> So, my question is, how did Supermarine get their R engines for 1931? Did RR, out of the goodness of their heart give the enginese to Supermarine or did they buy them from RR with Lady Houston's donation? It would seem that there is more to the story. Surely the Air Ministry would try to preserve their pride by refusing RR to allow the engines to Supermarine. Possibly Lady Houston had influence in high places.



The RAF performed a _volte face _in January 1931 and agreed to support the Schneider Trophy entry, and the High Speed Flight was re-formed at Calshot...but this was only 9 months before the race. The £100K from Lady Houston was only to cover the additional costs of the Schneider Trophy race, over and above what was already contracted with Rolls Royce and Supermarine. Thus, her contribution probably landed in R.J. Mitchell's lap around the same time as the RAF agreed to support the effort.

I'm pretty sure Supermarine did no preparation for the 1931 race after the RAF withdrew funding in late 1929/early 1930. In many respects, it was the lack of time between the funding tap being turned on and the actual race that limited the refinements to the S6, leading to the S6B. There are some tasks that simply can't be accelerated, and major redesign of an airframe is one of those things....try to speed it up too much and you'll either end up with a crap design or a smoking heap and a dead pilot (or both).

As for the Rolls Royce R development, that seems to have entirely stalled in 1930. Looking at this table that records the individual histories of each of the R engines, the only actions undertaken in 1930 were devoted to non-aviation applications of the engine (e.g. direct-drive shafts to power water speed record attempts):









Rolls-Royce R - Wikipedia







en.wikipedia.org





There isn't a single event in 1930 related to aviation applications of the R engine. That strongly suggests that Rolls Royce also ceased development of the R during that period, with things only picking up after the RAF involvement was re-energized in January 1931.

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## buffnut453 (Jul 10, 2022)

I remain perplexed at the persistence of the myth that the Supermarine S6B led directly to the Spitfire. After all, does anyone claim that the Macchi C200, C202 or C205 are direct descendants of the M52, M67 or M72 Schneider Trophy racers? How about the Curtiss P-36 evolving from the R3C-2, R3C-4 or the F6C-1? If there isn't any parental linkage within those manufacturers' lines, then why do we apply one to Supermarine?

Immediately following the 1931 Schneider Trophy race, the Air Ministry issued Specification F.7/30 as a proposed replacement for the Gloster Gauntlet. Supermarine responded with the Type 224 which is pictured below. A Spitfire it ain't:












The Supermarine Type 224 was powered by a Rolls Royce Goshawk engine and employed evaporative cooling. Note that the Goshawk was developed from the Kestrel and NOT from the R engines. It was ultimately unsuccessful (its top speed was just 228 mph) in competing for the F.7/30 specification. The winning aircraft was the Gloster Gladiator. 

Mitchell had further discussions with the Air Ministry to try and sell the Type 224. He proposed a different wing, tail and engine configurations that theoretically would increase the top speed to 265 mph. However, the Air Ministry felt that an entirely new design was required rather than evolutions of the 224. This thinking was driven, in part, by growing recognition that "modern" fighters would need at least 8 rifle calibre machine guns and the Type 224 could only carry four. 

Following the failure of the Type 224, Mitchell went back to the drawing board to create the Type 300 which was much more like what we know as a Spitfire. However, it was a completely different design from the Type 224, with retractable undercarriage, enclosed cockpit, and (eventually) the thin, elliptical wing that became the hallmark of the Spitfire design.

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## GregP (Jul 10, 2022)

Uuhhh, Bufnut, 

I wasn't the one claiming the linkage between the Schneider Cup and the Spitfire. It's all the pesky references saying that. Just FYI.

Maybe Vought-Sikorsky stole the Corsair's inverted gull wings from Supermarine? And moved the bullseye back a bit for pilot comfort.


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## buffnut453 (Jul 10, 2022)

GregP said:


> Uuhhh, Bufnut,
> 
> I wasn't the one claiming the linkage between the Schneider Cup and the Spitfire. It's all the pesky references saying that. Just FYI.
> 
> Maybe Vought-Sikorsky stole the Corsair's inverted gull wings from Supermarine? And moved the bullseye back a bit for pilot comfort.



I know. My last post wasn't an oblique reference to you. It was a general rant about the common associations of the Supermarine S6 and Spitfire. IMHO, the Spitfire was descended from the S6 in the same way that the Hurricane was descended from the Sopwith Snipe. 

Re the Corsair...you may be right. The wing/undercarriage set-up on the Type 224 also reminds me of the Stuka.


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## Shortround6 (Jul 10, 2022)

Lets see.

They both use a propeller in the Front.................................................................👍
They both use a propeller attached to the engine (no shaft).....................👍
They both put the pilot behind the engine........................................................👍
They both use a single vertical fin and rudder.................................................👍
They both use single horizontal stabilizer at the rear of the plane.........👍 

They both use the same airfoil...............................................................................👎
They both use the same wing planform (shape).............................................👎
They both use the same wing contruction........................................................👎
They both use landing flaps....................................................................................👎
They both store fuel in the fuselage....................................................................👎


At quick look the S6B and the Supermarine 300 seem to have in common that they both are tractor low wing monoplanes with a conventional engine installation and a conventional tail. 
At least this had a cantilever wing and had the fuel tank in the fuselage.

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## Frog (Jul 11, 2022)

Reluctant Poster said:


> American tanks were rationed in their use of HVAP ammunition (tungsten cored) for the same reason.



Another reason was that, according US doctrine, the tank destroyers, tasked with anti-tank mission, had higher priority for HVAP resupply, while the tank job was infantry support.


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## rinkol (Jul 11, 2022)

tomo pauk said:


> Why would one end up with a monster-sized fighter powered by a turbo V-1710?
> The gas hog was patiently faster, more rugged and heavier armed than any fighter of ww2.


You need ducting for air and exhaust gases and an intercooler in addition to the compressor/turbine combo. You either end up with a cockpit near the tail (XP-37) or run the ducting past the cockpit (Fw 190C and XP-60A). The latter spoils the advantage of the in-line engine in minimizing frontal area.


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## GregP (Jul 11, 2022)

"Development" doesn't mean "looks like."

It means similar design and/or construction. As for the Schneider Cup engines becoming the Merlin, Rolls-Royce might not have known what WORKED, but they likely had a definite handle on what DIDN'T WORK. Many things built from Legos don't look all that similar, but all are just a collection of boxes stuck together.

Many design features of the Merlin came from the Buzzard and the Type R engines. The sum of what Rolls Royce had learned making production and racing engines resulted in the Merlin and Griffon (basically a bored out Merlin type engine), particularly the Buzzard and the Type R ... according to many sources that are not me. I'm old, but I wasn't around when the Merlin was being designed.

Moreover, I have no stake in whether or not the claim is true. However it came to be, the Merlin was and is a good one!

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## markstuk (Jul 11, 2022)

tomo pauk said:


> Why would one end up with a monster-sized fighter powered by a turbo V-1710?
> The gas hog was patiently faster, more rugged and heavier armed than any fighter of ww2.


Heaviest armament? 4 x 20mm hs cannons as in the tempest are significantly more destructive than 8 X .50's..

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## Frog (Jul 11, 2022)

buffnut453 said:


> I know. My last post wasn't an oblique reference to you. It was a general rant about the common associations of the Supermarine S6 and Spitfire. IMHO, the Spitfire was descended from the S6 in the same way that the Hurricane was descended from the Sopwith Snipe.
> 
> Re the Corsair...you may be right. The wing/undercarriage set-up on the Type 224 also reminds me of the Stuka.



And the Stuka was developped around a RR Kestrel...

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## Thumpalumpacus (Jul 11, 2022)

Frog said:


> And the Stuka was developped around a RR Kestrel...



So was the Me-109, no?

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## Frog (Jul 11, 2022)

Thumpalumpacus said:


> So was the Me-109, no?


And also fitted with a RR Merlin...

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## Shortround6 (Jul 11, 2022)

GregP said:


> the Merlin and Griffon (basically a bored out Merlin type engine), particularly the Buzzard and the Type R .



The Buzzard and the R and the Griffon all used the same bore and stroke. The Buzzard and R predated the Merlin (Merlin is a reduced bore and stoke R?) and the Griffin I was running in 1933. The RR PV 12 first ran in Oct 1933 which really makes it hard for the Buzzard and R to be a bored out Merlin, even basically, unless Dr. Who was on the design team. 

Airplane engine makers were an lot less prone to boring out engine than they were to modifying engines of the same bore and stoke to operate at higher rpm or higher pressures or both. 

You may have to go deeper into the details, like different numbers or types of piston rings. Any notes on valves or valve timing. We know that the R changed to articulating connecting rods. The Merlin went back fork and blade rods. 
RR learned a lot, but that doesn't mean the Merlin was scaled down or modified in any large way from the early engines. 
Rowledge had worked at Napier and had a pretty good idea of what it took Napier to get the Lion engine up to 900hp or more in the earlier Schneider trophy racers. 
It doesn't seem like


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## Reluctant Poster (Jul 11, 2022)

Its all explained here!






Rolls-Royce Merlin and Kestrel - Wonders of World Aviation


Representative of the name of Rolls Royce today are the Kestrel and Merlin types of engines, both of which are extensively used in high-performance service aircraft, and are described in this chapter.




www.wondersofworldaviation.com

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## Reluctant Poster (Jul 11, 2022)

tomo pauk said:


> They probably did. Again, unfortunately, the effects of whatever the improvements they whipped up for the V-1710 seem to be very, very elusive until too late. If someone can correct me on this I'd be very grateful.
> 
> 
> 
> ...


I gathered together the NACA vs Allison reports I have and attached them as you note NACA were a little late for implementation

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## Reluctant Poster (Jul 11, 2022)

Reluctant Poster said:


> I gathered together the NACA vs Allison reports I have and attached them as you note NACA were a little late for implementation


Hers a couple more.


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## Reluctant Poster (Jul 11, 2022)

Piper106 said:


> Per Dan Whitney in "Vee's for Victory"
> XP-82 was to be powered with the Packard Merlin V-1650-23/25
> XP-82A would have the Allison F32R/L V-1710-119/121 (Aircraft cancelled)
> P-82B Allison offered the F33 R/L engine but the planes were produced with Merlin engines.
> ...


The Bendix SD-400 was the Rolls Royce injection system built under license. Interesting it went on to have a long career in the big air-cooled V12s that powered the M46, 47 and 48 tanks.
Also note that the reliability of the G series engines left a lot to be desired


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## Reluctant Poster (Jul 11, 2022)

Shortround6 said:


> A few corrections.
> The Kestrels did not start with superchargers, in service, although designed for them. They were soon added but both supercharged and non-supercharged Kestrels were offered for quite some time during the same period. The Kestrel was even offered with two different compression ratios in the unsupercharged form depending on fuel and intended use of the engine. Instructions for the "F" engine said that full throttle was not to be used below 2,000ft in the moderate compression engine, below 3,000ft in the high compression engine or below 11,500ft with the supercharged engine. Later supercharged Kestrels offered different compression ratios and different supercharger gears.
> 
> The Buzzard was always supercharged although both compression ratio and boost were limited. Sales were also limited. Most airframe makers couldn't quite figure out what to do with it.
> ...


According to Schlaifer in Development of Aircraft Engines "The 1929 engine was changed principally by the use of a higher supercharger gear ratio and a larger air intake; still more power was to be got by running the engine at higher speed. This increased output meant, however, that changes had to be made in virtually every Stressed part of the engine. It was necessary to replace the blade-and-fork with articulated rods, and salt-cooled exhaust valves were used for the first time on any Rolls Royce engine."


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## don4331 (Jul 11, 2022)

Shortround6 said:


> RR placed Buzzard/Griffon on hold in 1933. This derated R engine was run in 1933 but not flown in aircraft. In 1938-39 they started back up again with the reconfigured/smaller on the outside Griffon II engine first run in Nov 1939. This was the engine the RN was looking at in it's 1940-41 aircraft.


Just to nit pick:
Isn't the de-rated R/Griffon (no version) the engine from '33. 

Then you have the '38 request from FAA for an engine larger than Merlin (to accommodate additional weight of naval accessories - dingy, observer, wing fold, arrestor gear, catapult spools, naval radio), which results in the Griffon I of Nov/'39 with ~1,300hp.

But Merlin development is already on course to surpass that power/Air Ministry would like to see the engine in Spitfire. Which gets you the redesign resulting in the Griffon II which 1st runs in June/'40.


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## wuzak (Jul 12, 2022)

don4331 said:


> Just to nit pick:
> Isn't the de-rated R/Griffon (no version) the engine from '33.
> 
> Then you have the '38 request from FAA for an engine larger than Merlin (to accommodate additional weight of naval accessories - dingy, observer, wing fold, arrestor gear, catapult spools, naval radio), which results in the Griffon I of Nov/'39 with ~1,300hp.
> ...



Griffon I was the detuned R. 

Griffon II was newly designed engine starting in 1938 or 1939, which changed during development to allow it to be used in the Spitfire. The main changes, IIRC, related to the disposition of the accessories.


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## wuzak (Jul 12, 2022)

GregP said:


> "Development" doesn't mean "looks like."
> 
> It means similar design and/or construction. As for the Schneider Cup engines becoming the Merlin, Rolls-Royce might not have known what WORKED, but they likely had a definite handle on what DIDN'T WORK. Many things built from Legos don't look all that similar, but all are just a collection of boxes stuck together.
> 
> ...



One of the main design differences between the PV12/Merlin I and the Buzzard/R was the use of the "Ramp Head". This was like a pent roof style chamber/but angled, and owed its design to Rolls-Royce car engines.

The use of the Ramp Head meant that the PV12/Merlin had separate cylinder heads, whereas the Kestrel/Buzzard/R all had block and head as a single casting. Early Merlins also used a single casting for upper crankcase and cylinder blocks.

The Ramp Head did not live up to expectations, and there was difficulty in producing the single piece crankcase/block casting, so both were dropped and the Merlin was redesigned for the Merlin II. This was redesigned along Kestrel lines - single piece block/heads, separate crankcase, flat combustion chamber with parallel valves.

It was found that there were issues in sealing the cylinder liners in these castings, so the block and head were redesigned again, this time to have separate block and head. This was being done about the time that Packard was setting up to produce the Merlin, so they started with the separate block and head design.

The Griffon II was a vastly improved design compared to the Merlin. It had the bore and stroke dimensions of the Buzzard/R/Griffon I, but shared very little else.


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## wuzak (Jul 12, 2022)

Shortround6 said:


> You may have to go deeper into the details, like different numbers or types of piston rings. Any notes on valves or valve timing. We know that the R changed to articulating connecting rods. The Merlin went back fork and blade rods.



The 1929 R had fork and blade rods, but with the increased boost and power being produced for 1931 there were issues with the rods and bearings, so an articulated rod system was developed.


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## Reluctant Poster (Jul 12, 2022)

Reluctant Poster said:


> According to Schlaifer in Development of Aircraft Engines "The 1929 engine was changed principally by the use of a higher supercharger gear ratio and a larger air intake; still more power was to be got by running the engine at higher speed. This increased output meant, however, that changes had to be made in virtually every Stressed part of the engine. It was necessary to replace the blade-and-fork with articulated rods, and salt-cooled exhaust valves were used for the first time on any Rolls Royce engine."


I should have made clear that this is describing the changes made for the 1931 race.


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## wjkuleck (Jul 13, 2022)

In the view of this once-upon-a-time aero engineer, the P-39 was the victim of its layout, combined with its diminutive size. The big gun and nosewheel filled the space where you would find the engine and a fuel tank. The water and oil coolers occupied the space where fuel might have been. 

The XP's turbo and intercooler had no proper space; the internal ducting was cramped and the installation draggy. In retrospect the use of a turbo for the second stage of supercharging was a dismal idea given the packaging possibilities. The result of the NACA wind tunnel work was the determination that the turbo installation had to go.

At that point the world needed fighters, so the '39 went ahead despite its altitude limitations. The only remedy, the two stage Allison, was too long* for the '39's fuselage. Alas, the lack of fuel capacity limited its usefulness, although the P-40 didn't outrange it by much.

The P-63 was a larger airframe to accommodate the two stage Allison. Alas, the layout continued to limit its fuel capacity. The Kingcobra could hold its own with the Merlin Mustang, with the crucial difference of much shorter range. The Soviets loved the King because they didn't need Mustang range. The King hung on long enough in the VVS that a couple of F-80s that "accidentally" crossed the Korean border into Russia shot up an airfield staffed with P-63s---in 1950.

* a two-stage Allison was shoehorned into an XP-39E after lengthening its fuselage by 21 inches.

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## Reluctant Poster (Aug 21, 2022)

Shortround6 said:


> Allison especially and for very good reason.
> 
> In the spring/summer of 1939 the government owed Allison over 900,000 dollars for work already done.
> 
> ...


According to Whitney GM started building Allison Plant No3 without a firm order from the air force
$500,000 was petty cash for GM in the 1930's. They were investing millions in all sorts of new fields. for instnce, they were about to revolutionize the small diesel with their legendary 71 series. Even though they have already invested in the development of large diesels for US submarines they were spending millions on a clean sheet design for the even more legendary EMD 567 which obliterated the steam engine. They built a brand-new plant to build diesel locomotives which at that time was a market that barely existed. There is a story in Sloanes book in which Hamilton asks for $500,000 to develop the 567 which Sloane says in his experience will not be enough.

In cars they were developing the world first mass produced automatic transmission the Hydramatic. Maurice Olley was doing seminal research on car suspensions which resulted in completely new designs. They were investing millions in new methods of constructing car bodies the revolutionary "turret top" which gave us my favorite ad of all time

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## SaparotRob (Aug 21, 2022)

Great stuff!


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## Shortround6 (Aug 21, 2022)

Reluctant Poster said:


> According to Whitney GM started building Allison Plant No3 without a firm order from the air force


Did they have a letter of intent? The two could often be separated bey several months.
Or was GM reacting to the XP-40 winning the Jan 1939 fighter competition and anticipating orders?


Reluctant Poster said:


> $500,000 was petty cash for GM in the 1930's. They were investing millions in all sorts of new fields. for instnce, they were about to revolutionize the small diesel with their legendary 71 series.


I am not sure it was petty cash, GM didn't want to waste money. If they could see a market they were willing to spend money. If the market was slow materializing then they may have been more cautious. GM had built over 700 6-71 diesels in 1937, they were sticking them in boats, small locomotives, crawler tractors and trucks and buses. The potential for growth was there. Especially considering what the gasoline engine selection for such use was. 


Reluctant Poster said:


> Even though they have already invested in the development of large diesels for US submarines they were spending millions on a clean sheet design for the even more legendary EMD 567 which obliterated the steam engine. They built a brand-new plant to build diesel locomotives which at that time was a market that barely existed.


and again, what was the potential market?
GM had been pushing the locomotive diesel engine for most of the 30s.
The US economic times from 1929 on affecting things quite a bit. A few existing companies withdrew from the market or became suppliers of components. The Railroads were cutting back investment but were looking for cost savings. in the mid 30s enough demonstrators had been fielded and/or enough low power switch locomotives had been built to build up demand. 
The Market was there, it was well researched and in 1939-40 the order books were starting to fill up. 
The War Production Board stopped a large amount of locomotive production and routed large diesels to warships. This skewed the market for diesels during the war and helped preserve the steam locomotive as did the petroleum shortage of 1942-43, a bit after the time in question but helps explain the slow growth in the diesel market during the war. 

The Allison engine in 1938 and the first few months of 1939 was much more of a gamble. It had promise but it very little in the way of sales. Could the Allison break into the market against P & W, Wright, Continental and Lycoming? The last two made a range of industrial and motor vehicle engines in addition to aircraft engines. 
The commercial airlines showed no sign of switching to a liquid cooled engine. The navy showed very little interest after the airships went away. 
In 1938 could GM depend on the army alone to order enough engines to make Allison profitable?

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## special ed (Aug 21, 2022)

Reluctant Poster said:


> According to Whitney GM started building Allison Plant No3 without a firm order from the air force
> $500,000 was petty cash for GM in the 1930's. They were investing millions in all sorts of new fields. for instnce, they were about to revolutionize the small diesel with their legendary 71 series. Even though they have already invested in the development of large diesels for US submarines they were spending millions on a clean sheet design for the even more legendary EMD 567 which obliterated the steam engine. They built a brand-new plant to build diesel locomotives which at that time was a market that barely existed. There is a story in Sloanes book in which Hamilton asks for $500,000 to develop the 567 which Sloane says in his experience will not be enough.
> 
> In cars they were developing the world first mass produced automatic transmission the Hydramatic. Maurice Olley was doing seminal research on car suspensions which resulted in completely new designs. They were investing millions in new methods of constructing car bodies the revolutionary "turret top" which gave us my favorite ad of all time



Watching, with my father in law, a documentary about the first concrete multi lane roads in California, the camera was filming a new 1936 Chevrolet from the front as it drove along. My father in law said, "If we had roads that good, we would still be driving 36 Chevvys."

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## FLYBOYJ (Aug 21, 2022)

Reluctant Poster said:


> *According to Whitney GM started building Allison Plant No3 without a firm order from the air force
> $500,000 was petty cash for GM in the 1930's.* They were investing millions in all sorts of new fields. for instnce, they were about to revolutionize the small diesel with their legendary 71 series. Even though they have already invested in the development of large diesels for US submarines they were spending millions on a clean sheet design for the even more legendary EMD 567 which obliterated the steam engine. They built a brand-new plant to build diesel locomotives which at that time was a market that barely existed. There is a story in Sloanes book in which Hamilton asks for $500,000 to develop the 567 which Sloane says in his experience will not be enough.
> 
> In cars they were developing the world first mass produced automatic transmission the Hydramatic. Maurice Olley was doing seminal research on car suspensions which resulted in completely new designs. They were investing millions in new methods of constructing car bodies the revolutionary "turret top" which gave us my favorite ad of all time



$500,000 in 1938 dollars is well over 10 million in today's dollars and even though GM was a large corporation back then, this was a depression era and no big corporation was going to make an investment like this unless they are going to get a return. The individual(s) responsible for the business sector behind something like this would probably lose his/ their job(s) and wreck his/their career if this investment wasn't profitable. Just ask Alexander P. de Seversky.

In the bigger picture, once again you miss the fact that large *aircraft companies* normally do not risk development of a technology unless they know they have a contract in hand or they are pretty certain they can sell their product at a later date. You can't compare the manufacture of diesel engines, automatic transmissions or any other automotive products to the aviation industry of the late 1930s, especially when technology was continually expanding and the future was so uncertain.

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## GregP (Aug 21, 2022)

Reluctant Poster said:


> The Bendix SD-400 was the Rolls Royce injection system built under license. Interesting it went on to have a long career in the big air-cooled V12s that powered the M46, 47 and 48 tanks.
> Also note that the reliability of the G series engines left a lot to be desired



The highest F-series Allison V-1710 was the F32 (V-1710-119).

There was no F36R or F36L. The -143 and -145 were always G-series engines.


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## Jugman (Aug 22, 2022)

By the time GM ponied out that initial half million for plant 3 they had invested 3.8 million in Allison. That's not including the 10 million they paid to buy Allison. Allison spent most of the 1930s in the red. Honestly I can see why Hazen and Hunt didn't push for more funding by GM. I think it's next to impossible that they would have put more into r&d.

As it was Allison probably spent more money on liquid cooled development then every other us manufacturer combined.

Two corrections
I meant Kreusser not Hunt. 
GM only paid $600,000 plus an additional $200,000 for needed improvements. I'm not sure where I got $10 million from. Regardless it took Allison a decade to for net profits to equal the purchase price.

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## Shortround6 (Aug 22, 2022)

Allison at the time was making decent money (or even very good money at times) making bearings. 

It was the "engine division" of Allison that was in the red. 

Not sure where the part of the company that built the propeller drive systems for the Akron and Macon were in the company structure?

Gone by 1938-39 or building the extension shafts for Bell Airacuda?


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## Jugman (Aug 22, 2022)

Shortround6 said:


> Allison at the time was making decent money (or even very good money at times) making bearings.
> 
> It was the "engine division" of Allison that was in the red.
> 
> ...


Allison didn't have any internal divisions back then. They were far too small for that.


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## GregP (Aug 22, 2022)

The shop was on Speedway row just outside the Indianapolis 500 race track, and it wasn't all that big. Allison moved to Florida after WWI, but left Norman Gillman in charge of the Indiana shop. Eddie Rickenbacker bought Allison Engines in 1927 and sold it to Fisher Brothers, who sold it to General Motors. In 1995, Allison was acquired by Rolls Royce, and they finally had a great source for main bearings that was owned by them.


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## glennasher (Aug 26, 2022)

GregP said:


> The shop was on Speedway row just outside the Indianapolis 500 race track, and it wasn't all that big. Allison moved to Florida after WWI, but left Norman Gillman in charge of the Indiana shop. Eddie Rickenbacker bought Allison Engines in 1927 and sold it to Fisher Brothers, who sold it to General Motors. In 1995, ALlion was acquired by Rolls Royce, and they finally had a great source for main bearings that was owned by them.


A friend of mine (and a hunting buddy) worked for, and retired from, Allison/Rolls Royce a few years back. He was a metallurgist and they kept him busy with various requirements and he did a lot of traveling for them, too.

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## Reluctant Poster (Aug 29, 2022)

Shortround6 said:


> Did they have a letter of intent? The two could often be separated bey several months.
> Or was GM reacting to the XP-40 winning the Jan 1939 fighter competition and anticipating orders?
> 
> I am not sure it was petty cash, GM didn't want to waste money. If they could see a market they were willing to spend money. If the market was slow materializing then they may have been more cautious. GM had built over 700 6-71 diesels in 1937, they were sticking them in boats, small locomotives, crawler tractors and trucks and buses. The potential for growth was there. Especially considering what the gasoline engine selection for such use was.
> ...


GM made the momentous decision to basically reinvent the locomotive in 1935.
In February 1935 Richard Dilworth, EMCs chief engineer, proposed the idea of a joint factory for Electro Motive and Winton to a meeting of GMs top management.
From the article "Daybreak at La Grange" in the August 1976 issue of Trains magazine:
"Dilworth reportedly told the automotive –oriented crowd that "their cars and trucks were nothing but rubber-tired toys. I told 'em that if that filled the highways solid with these toys they wouldn't be able to do a quarter of the transportation business of the country" Dilworth spoke his beliefs minus any niceties of speech, he also doubted his one-million-dollar request would be approved. In a meeting afterward with GM executives, EMC founder and president H. L. Hamilton was told to proceed with plans to proceed with plans to build a factory. He informed Dilworth that the giant automotive firm was ready to invest six million dollars in Dilworth's idea. The following month, on March 27, 1935, Hamilton and Dilworth broke ground for the plant…."

There are several things to note:
1. The locomotive market was virtually nonexistent except for diesel switchers. America's largest builder, Alco, did not produce any steam locomotives in 1934 and 35.

2. Even the diesel switcher market was minuscule. In 1930 Class 1 railroads rostered 74 diesels; in 1935 they had 113, an increase of only 29 over a period of 5 years. Sales of diesels locomotives at that time were not driven by operational efficiency but rather to meet city smoke ordinances. Kaufman Act - Wikipedia. Diesel switchers were concentrated in New York and Chicago with the steel industry acquiring quite a few. Alco had developed the modern form of the switcher in the HH600 in 1931 but had only built 13 up to 1935.

3. At this time EMC did not build anything. Engines came from Winton, electrical equipment from GE, with final assembly by the car body supplier. GM was entering a whole new world. Building a 90 ton locomotive was nothing like anything GM had done before. In Feb 1935 EMC was in the process of delivering their first 3 switchers. The first of the 5 larger boxcabs for passenger road service would not be completed until August 1935. With the odd ball double end transfer unit for the IC, that was the entire EMC production of 9 locomotives for 1935, all assembled by GE, St Louis Car or Bethlehem Steel.

4. The Winton 201A was not in any sense proven. Only a single Winton 201A in the original Zephyr had any significant running experience. The second 201A powered train set Union Pacific's M-10001 had entered service in Oct 1934 but was soon withdrawn for rebuilding. Incidentally, none of the 201A powered USN submarines been launched. Over a year later La Grange completed its first locomotive, an SC, on May 20, 1936.
The Winton 201A cannot be considered to be a successful engine. EMC and Cleveland Diesel (as Winton became known) started on clean sheet replacements well before large numbers of the 201A were in service. It was a failure in its original application with the USN repowering their submarines in 1942. The 201A powered passenger boxcabs and Es were all out of service by 1953, most "rebuilt" into 567 powered models, a short life for a locomotive. The switchers did better but again of lot of them were reengined with 567s

5. As to a large order book, GM was actually building on spec. They reduced the price of the SC from $84,000 to $70,000 on the assumption that there would be a run of 50 locomotives of the same design. They actually completed 24 by the end of 1936

6. The Pennsylvania railroad was by far the biggest in the USA. the New York Central was easy the second biggest. The next three; the Union Pacific, Southern Pacific and Sante Fe were about equal in size. The UP and Santa Fe have a few passenger trains but that was the extent of their interest. Of the 175 201A engined switchers NYC bought 7, Santa Fe 7 and the Pennsy 1. UP and SP didn't buy any. It wasn't until the war started that Sante Fe began to buy diesel locomotives in earnest. The other 4, particularly the Pennsy and NYC resisted dieselization as long as they could. While the Sante Fe embraced dieselization whole heartedly the other 4 didn't start buying diesels in significant numbers until after WWII.

.

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## Admiral Beez (Aug 31, 2022)

CobberKane said:


> Was there any intrinsic design feature that precluded Allison engines from powering single engine fighters…..


What about the RR Meteor? Was the Allison considered for AFVs?


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## Shortround6 (Aug 31, 2022)

Not really. 

The timing was off. 

Allison made the following engines 

1940...........................1,149
1941............................6,402
1942.........................14,904
1943.........................21,064
1944.........................20,191

Until some point in late 1943 or 1944 Allison could not build aircraft engines fast enough. And in 1944 the US had sorted out the engines for the M4 Sherman and were retiring the the odd balls or sending them off in lend-lease Tanks. 
The US Army kept the Ford V-8 and the Continental radials for themselves and sent the Diesel powered tanks to the Marine Corp (thousands of Landing craft used the same engines/fuel) and to the British and to the Soviet union. 

Trying to build a V-8 or V-12 Allison in 1944/45 wasn't going to solve anything


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## FLYBOYJ (Aug 31, 2022)

Reluctant Poster said:


> GM made the momentous decision to basically reinvent the locomotive in 1935.
> In February 1935 Richard Dilworth, EMCs chief engineer, proposed the idea of a joint factory for Electro Motive and Winton to a meeting of GMs top management.
> From the article "Daybreak at La Grange" in the August 1976 issue of Trains magazine:
> "Dilworth reportedly told the automotive –oriented crowd that "their cars and trucks were nothing but rubber-tired toys. I told 'em that if that filled the highways solid with these toys they wouldn't be able to do a quarter of the transportation business of the country" Dilworth spoke his beliefs minus any niceties of speech, he also doubted his one-million-dollar request would be approved. In a meeting afterward with GM executives, EMC founder and president H. L. Hamilton was told to proceed with plans to proceed with plans to build a factory. He informed Dilworth that the giant automotive firm was ready to invest six million dollars in Dilworth's idea. The following month, on March 27, 1935, Hamilton and Dilworth broke ground for the plant…."
> ...


Great information but what does this have to do with the development of aircraft engines during the late 1930s and the ability to gain a government contract (and hopefully get the customer to pay for R&D costs)?


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## Milosh (Aug 31, 2022)

Shortround6 said:


> The US Army kept the Ford V-8


Wasn't this engine based on the Merlin?


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## swampyankee (Sep 1, 2022)

Milosh said:


> Wasn't this engine based on the Merlin?


No. It was based on an engine Ford offered to mass produce in lieu of the Merlin.


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## Geoffrey Sinclair (Sep 1, 2022)

FLYBOYJ said:


> Great information but what does this have to do with the development of aircraft engines during the late 1930s and the ability to gain a government contract (and hopefully get the customer to pay for R&D costs)?


I think the idea is every so often large companies will try and create a market. Part of the GM thinking was they could move the rail companies from build your own to buy off the shelf. The depression also stopped a number of US diesel makers, opening up the market. GE would have an idea about the performance of the best German versions, plus the USN desire for high performance diesels, the 1931 USN attempt to buy European engines for trials was blocked by congress. Yet the USN BuEng thought diesels suitable for fast locomotives were the ones for submarines, versus switcher engines which could be much heavier, with its own diesels GE could provide the complete submarine propulsion package. The USN started using "modern" GE diesels in the mid 1930's.

Back to aircraft, The CAA reports V-1710 production was 1,141 in 1940, 6,447 in 1941, 14,905 in 1942, 21,063 in 1943, 20,191 on 1944, the War Production Board agrees but notes one 2 stage in 1942, 514 in 1943 and 2,867 in 1944. That gives 43,492 engines 1940 to 1943, while new P-38+P-39+P-40+Allison P-51+A-36 production for the time period required 27,929 engines plus spares, somewhere between 20 and 33% of numbers fitted to new aircraft. Plus stocks ready to be fitted to the early 1944 production.

Now to complete, from sea to air to land. When it comes to tank engines the need was in 1943. The US cut back production in 1944.

Sherman production peaked in July 1943 at 2,401 and was down to 508 in February 1944 before picking up again. The US had 10 Sherman production lines December 1942 until September 1943 then down to 7 in December and 3 in February 1944. This includes the short lived Canadian line (October to December 1943). It means 29,450 out of 49,422 Shermans were built to end 1943, then another 13,179 in 1944, down from 21,433 in 1943.

The M4 ceased production in March 1945, the M4A1 in July 1945, (both Continental R-975) the M4A2 (GM Diesel) in May 1945, the M4A3 in June 1945 (Ford GAA V8) (plus a pause October 1943 to January 1944), the M4A4 (Chrysler Multibank) in September 1943 and the few diesel M4A6 in February 1944.

The 1944 mix was 1,432 M4, 2,171 M4A1, 2,428 M4A2, 7,089 M4A2 and 59 M4A6. When it comes to allocations the US mostly kept the 76 and 105mm gun armed Shermans.
M4 All from February 1944 on were 105mm, 
M4A1 all 1944 or later were 76mm gun armed.
M4A2 Fisher built 843 75mm January to May 1944, otherwise all 1944 or later M4A2 were 76mm gun armed.
M4A3 in 1944/45 came in 75mm (3,325), 76mm (4,542) and (3,039) 105mm

HVS appeared in January 1945 for the 75mm gun, August 1944 for the 76mm and September 1944 for the 105mm gun versions.

The big army equipment push in 1942/43 also included the tank destroyers and SP artillery, which used the same engines as the Sherman, and production also tapered off in 1944, production of 7,518 tank destroyers to end 1943, 3,095 in 1944, 2,814 M7 to end 1943, 1,164 in 1944 .

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## Admiral Beez (Sep 1, 2022)

Milosh said:


> Wasn't this engine based on the Merlin?


There was a V-8 based on the Merlin. The Meteorite. Available in both diesel and gas versions.


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## Milosh (Sep 1, 2022)

swampyankee said:


> No. It was based on an engine Ford offered to mass produce in lieu of the Merlin.


When the deal went south to build Merlins, Ford used the Merlin drawings as a base for the Ford engine.


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## FLYBOYJ (Sep 1, 2022)

Geoffrey Sinclair said:


> I think the idea is every so often large companies will try and create a market.


Well I can tell you that assumption is generally wrong with regards to pre war military aviation. 


Geoffrey Sinclair said:


> Part of the GM thinking was they could move the rail companies from build your own to buy off the shelf. The depression also stopped a number of US diesel makers, opening up the market. GE would have an idea about the performance of the best German versions, plus the USN desire for high performance diesels, the 1931 USN attempt to buy European engines for trials was blocked by congress. Yet the USN BuEng thought diesels suitable for fast locomotives were the ones for submarines, versus switcher engines which could be much heavier, with its own diesels GE could provide the complete submarine propulsion package. The USN started using "modern" GE diesels in the mid 1930's.


Apples and oranges


Geoffrey Sinclair said:


> Back to aircraft, The CAA reports V-1710 production was 1,141 in 1940, 6,447 in 1941, 14,905 in 1942, 21,063 in 1943, 20,191 on 1944, the War Production Board agrees but notes one 2 stage in 1942, 514 in 1943 and 2,867 in 1944. That gives 43,492 engines 1940 to 1943, while new P-38+P-39+P-40+Allison P-51+A-36 production for the time period required 27,929 engines plus spares, somewhere between 20 and 33% of numbers fitted to new aircraft. Plus stocks ready to be fitted to the early 1944 production.
> 
> Now to complete, from sea to air to land. When it comes to tank engines the need was in 1943. The US cut back production in 1944.
> 
> ...


All good - a contract was in place to make all this happen. No one works from free. 

Again, some aircraft companies will undertake R&D work at their own expense but will expect a return somewhere along the line and if possible have the "customer" help them recover the cost of the R&D work or have it priced into the contract.

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## Reluctant Poster (Sep 1, 2022)

FLYBOYJ said:


> Well I can tell you that assumption is generally wrong with regards to pre war military aviation.
> 
> Apples and oranges
> 
> ...


I am curious as to how much GM invested in North American pre war. That would be an apples to apples comparison. Perhaps Dragon Dog can tell us.


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## Shortround6 (Sep 1, 2022)

Milosh said:


> Wasn't this engine based on the Merlin?





swampyankee said:


> No. It was based on an engine Ford offered to mass produce in lieu of the Merlin.


Some things are a little murky. Not helped by Ford Fan Boy websites/facebook pages.

It is very close to unbelievable that they only started development in June of 1940 after seeing the Merlin engine and drawings. How long they had been working on the engine in secret is certainly subject to question.
Judging by bore and stroke gets a little tricky. Most aircraft engine designers liked to keep the bore and stroke ratio pretty close because of flame travel and expected rpm. Their goal was fuel burn being done at about 20 degrees after top dead center. Very few engines used variable ignition timing so the ignition timing has to be suitable for both idling and full speed (some engines could use retarded timing for starting).

The Merlin used SOHC valve arrangement, the Ford used DOHC.
The Ford used a pent roof combustion chamber.
The Ford used offset connecting rods and cylinders like a car engine, The Merlin used forked connecting rods and the left and right cylinders were lined up with each other.

These are fundamental differences and nobody is even looking at the actual crankshaft in regards to size and bearings (size and length).
Ford claimed they were going to use a cast crankshaft and rods (?) instead of forged. Maybe they got away with it on the tank engines but they ran the tank engines at lower rpm and used no supercharger. A much lighter load on the connecting rods and crankshaft.


_"When the deal went south to build Merlins, Ford used the Merlin drawings as a base for the Ford engine."_

This is often claimed but the boys at Ford must have been awful fast workers. 
Of course we have to define "based on". As noted above they changed the whole cylinder head and valve train and they changed the cylinder bock layout (one cylinder bank offset from the other). 
Maybe there were some details Ford used or they used the Merlin drawings to help refine calculations.

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## FLYBOYJ (Sep 1, 2022)

Reluctant Poster said:


> I am curious as to how much GM invested in North American pre war. That would be an apples to apples comparison. Perhaps Dragon Dog can tell us.


Now that would be an interesting to know as it was apparent that war was on the horizon and there would be a need for armaments, be it from the US or a foreign government. The gamble would be "when and how much."


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## Shortround6 (Sep 1, 2022)

Reluctant Poster said:


> I am curious as to how much GM invested in North American pre war. That would be an apples to apples comparison. Perhaps Dragon Dog can tell us.





FLYBOYJ said:


> Now that would be an interesting to know as it was apparent that war was on the horizon and there would be a need for armaments, be it from the US or a foreign government. The gamble would be "when and how much."



It is note quite apples to apples. 
NA was making the series of trainers starting with the NA-16 which flew in 1935. Both fixed gear and retractable and using several different engines. 
They also branched out into bomber design 





First flown in Dec 1936. No sales, sort of, evaluation batch was canceled. 
The NA-40 




was first flown in Jan 1939.
Please note that NA had built or had orders for several hundreds of trainer aircraft at this time and was making a profit, how big a one is subject to question. 

In Jan 1939 Allison engine division (as opposed to the bearing division) was not making a profit and was running at loss for quite a while. 
The XP-40 had won the Jan 1939 fighter competition and perhaps one could gamble that a production contract for the engines would be soon be coming. But the Army didn't actually make up it's mind until April of 1939. It also ordered 13 YP-39s and 13 YP-38s within a few days with that the future of the Allison engine was certainly more secure. 

Please remember that Continental was acting as the assembly shop for the ???-1430 engine (based on engineering from the Army) and Lycoming was dabbling with O-1230 engine and while both were later in timing than the Allison it was by no means assured that Allison had the "lock" on American liquid cooled engines. Both of these programs had been in existence for several years by Jan 1939 and the Continental engine was the Army's fair haired boy. 
Progress on the Continental was slow because Continental refused (unlike Allison) to do any new work on the engine until work already done had been paid for. Like two cylinder test rigs and rebuilds of the two cylinder test rigs. 

So Allison (GM) was in competition with with these two programs in addition to the two radial engine makers. 

Please note that both Continental and Lycoming were successful builders of smaller aircraft engines in addition to making car, truck and bus engines. Their corporation's future did not depend on the big aircraft engine although devoting too much time/effort could affect things.

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## drgondog (Sep 1, 2022)

Reluctant Poster said:


> I am curious as to how much GM invested in North American pre war. That would be an apples to apples comparison. Perhaps Dragon Dog can tell us.


I don't have the precise dollars or the financial mechanism GMC provided NAA but via Ernie Breech, the GMC Board mamber assigned to NAA, GMC provided project funding assistance for XO47 (at Dundalk, MD), BT-9, XB-21 and NA-40. The latter two, while not winning comptition against Douglas B-18 or A-20, firmly established NAA's reputation leading to B-25 contract. The BT-9 led to BC-1 and AT-6 plus several export fighter contracts giving NAA a solid reputation for quality and engineering excellence in Commonwealth contries as well as AAF.

The funding was generally limited to Projects, and was influential at NAA to imbed Production Engineering Projects in middle of advanced design to ensure design to production methodology was incorporated into airframe design. I have seen references suggesting GMC involvement in Q2 1941 in providing funds within NA-83 to design and Propose Allison Low Level Pursuit (A-36) to compete for AAF Dive Bombing Procurement. That said, I do not have any NAA Financial Management records or statements other than the multiple O Contractor Reports which detail all NAA Charge Number projetcs at summary level, but no breakout for total$, nor Direct vs Overhead breakouts or the Project/Contracts.

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## Snowygrouch (Sep 11, 2022)

Copying a 1940 spec merlin gets you just about nothing, no idea why anyone would do that. Also why on earth would RR just leave ford with the drawings if the deal fell through?

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## Reluctant Poster (Sep 11, 2022)

Snowygrouch said:


> Copying a 1940 spec merlin gets you just about nothing, no idea why anyone would do that. Also why on earth would RR just leave ford with the drawings if the deal fell through?


Maurice Olleys recollection of events with respect to Merlin drawings in this. 








The Ford's, the Merlins and Maurice Olley


Origins of Ford Aero and Tank Engines, the American Merlin, and the writings of Maurice Olley. Before the entry of the United States in the Second World War,…




thunderboats.ning.com




I do not agree with the authors conclusion that the Ford engine was superior to the Merlin, particularly with respect to the cast crankshaft. Post war Ford used forged cranks in the very big Super Duty V-8 used in tractor trailers.

Olley certainly had an interesting career. He was a part of the original design team for the original Eagle, but his real claim to fame is as a chassis designer.


https://millikenresearch.com/MauriceOlleybyWFMilliken.pdf



In March 1939 Rolls Royce entered discussions with Ford France to manufacture the Merlin III. From "Hives and the Merlin":
"Before the final details of the agreement had been completed a number of Ford engineers arrived at Derby to gain a general idea of the manufacturing techniques involved in Merlin production. Some of these men were from the parent company in Detroit and had worked on the Liberty project in the First World War. These engineers were given full run of the Derby factory and spent about 6 months there. Most of the informs passed back to Detroit, where the parent company was carrying out production planning of the entire scheme. The special machine tools, none of which were obtainable in France, were all ordered and progressed from the Dearborn headquarters of the Ford Company in Detroit."

"On August 21 there was a completely unexpected development at Dearborn. Henry Ford, who was not impressed by Britain's or France's chances of defeating a sustained German attack, decide to keep his American plants strictly neutral. As a result of this decision all Merlin and other armament work of any description was rapidly cleared out of the Ford factories and organization at Detroit."

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## tomo pauk (Sep 11, 2022)

Reluctant Poster said:


> Maurice Olleys recollection of events with respect to Merlin drawings in this.
> 
> 
> 
> ...



Unfortunately, the sentences (my emphasis):
_Like Packard, the British Ford factory redrew the RR drawings and *tightened the tolerances* so the engines could be mass produced._

and:

_The Ford GG aircraft V12 showed great potential, producing over 1800 Hp on its initial dyno test!_

don't have a connection with what actually happened.

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## buffnut453 (Sep 11, 2022)

tomo pauk said:


> Unfortunately, the sentences (my emphasis):
> _Like Packard, the British Ford factory redrew the RR drawings and *tightened the tolerances* so the engines could be mass produced._
> 
> and:
> ...



The whole "tightened the tolerances" remark smacks of lazily copying assertions made elsewhere that 

 Snowygrouch
has, IMHO, effectively debunked. Rolls Royce factories (multiple) produced far more Merlins than the Ford factory in the UK, so it makes little sense that somehow Ford went down its own path with tighter tolerances. To do so would prevent interchangeability of parts between Ford and Rolls Royce produced engines. 

Again, Merlin production totals for comparison:

Rolls Royce Factories:

Derby: 32,377
Crewe: 26,065
Glasgow: 23,675

Ford Factory, Manchester: 30,428

Packard Merlin Production: 55,523.

If Ford "tightened tolerances" then those different standards would have had to be replicated at all the Rolls Royce factories...and yet the Ford factory only started production in May 1941 whereas all 3 Rolls Royce factories were in production in 1939 or by mid-1940. 

I really do wish this myth about Rolls Royce's sloppy tolerances would die.

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## buffnut453 (Sep 11, 2022)

One other note, this from Wikipedia which isn't the best of sources. However, if it's true then it provides further evidence that Rolls Royce tolerances can't possibly have been sloppy:

_With 16,000 employees, the Glasgow factory was one of the largest industrial operations in Scotland. Unlike the Derby and Crewe plants which relied significantly on external subcontractors, it produced almost all the Merlin's components itself._

Now, if the Crewe and Derby factories relied on subcontractors to produce Merlin components, surely sloppy tolerances would have hindered the ability to mass-produce the engines? Yet Derby produced more Merlins than any other UK factory.

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## Shortround6 (Sep 11, 2022)

Reluctant Poster said:


> I do not agree with the authors conclusion that the Ford engine was superior to the Merlin, particularly with respect to the cast crankshaft. Post war Ford used forged cranks in the very big Super Duty V-8 used in tractor trailers.





tomo pauk said:


> The Ford GG aircraft V12 showed great potential, producing over 1800 Hp on its initial dyno test!



There are several possible things going on with the cast crankshaft/s.
I am saying _possible_ 

1 thing is how long were the crankshafts good for? 100 hours or 150 or 300 hours?

2, when you are comparing truck engines you run into a similar problem. Heavy duty truck engines spend a higher percentage of their lives at a higher power level than car or light duty trucks. Commercial trucks also spend a lot more hours per month (or per year) running than cars or light duty trucks. They have to have higher durability or the truck isn't making money. 

3, You may be able to design a suitable cast Iron crankshaft but it may not be interchange with with a forged crankshaft. The cast iron part may be bigger though the bearing journals and rod bearings? Some car engines came with cast cranks on light duty engines and forged cranks on heavy duty engines but they were interchangeable. 
In 1940 Allison was a lot of trouble with their crankshafts. Solved in part by shot peening the crankshafts and by the end of 1941/ start of 1942 by nitriding and shot peening the crankshafts. 
We have no idea if Ford would have been forced to change crankshaft construction. 

I would note that RR had gotten over 1800hp out of Merlin on the test stand in 1938 when working on the Speed Spitfire. 

What we don't know about the 1800hp Ford is for how long they made 1800hp and what the conditions were. 
Was the Ford using a two stage supercharger (mechanical supercharger plus turbo) or a single stage supercharger (turbo only) ?

Were they getting 1800hp at sea level ? or at altitude (many engine test houses could adjust the air pressure of the intake air). 

One might also wonder if the turbo was going to standup to those power levels. Every other production turbo spaced the turbo a number of feet further away from the engine to allow for a bit of cooling before the exhaust gases hit the turbo.

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## Shortround6 (Sep 11, 2022)

buffnut453 said:


> One other note, this from Wikipedia which isn't the best of sources. However, if it's true then it provides further evidence that Rolls Royce tolerances can't possibly have been sloppy:
> 
> _With 16,000 employees, the Glasgow factory was one of the largest industrial operations in Scotland. Unlike the Derby and Crewe plants which relied significantly on external subcontractors, it produced almost all the Merlin's components itself._
> 
> Now, if the Crewe and Derby factories relied on subcontractors to produce Merlin components, surely sloppy tolerances would have hindered the ability to mass-produce the engines? Yet Derby produced more Merlins than any other UK factory.




The thing is that "story" about the loose tolerances comes from Hooker in his autobiography. 
What may be missing is _when _guys for Ford were talking in the office the Hooker was sharing. Hooker, without giving dates, says that it took a year or so to redo the drawings. 

It may also assume that RR did not tighten things up at the RR factories. 

I would also note that you can have two different fit standards. 
One fit standard can have _every_ piston fit into any cylinder. This is what Ford was looking for. 
Another fit standard is that a Piston has to fit in a cylinder with a only a certain amount of clearance. If you have a cylinder that is a few thousands of in wider then you need to find a piston that fits that cylinder,
Not filing to fit.

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## buffnut453 (Sep 11, 2022)

Shortround6 said:


> The thing is that "story" about the loose tolerances comes from Hooker in his autobiography.
> What may be missing is _when _guys for Ford were talking in the office the Hooker was sharing. Hooker, without giving dates, says that it took a year or so to redo the drawings.
> 
> It may also assume that RR did not tighten things up at the RR factories.
> ...



I'm familiar with the origin of the story. For all his many talents, Hooker was not a production engineer. I also find it interesting that people just accept the Hooker comment without actually doing the leg-work to determine what tolerances were permitted and whether those tolerances changed over time. If Hooker's comment is to be taken at face value, then at some point in the period May 1940 thru May 1941, there MUST have been a change in tolerances at the RR factories to align with Ford's better production standards. Either that or Ford was producing engines at different tolerances to the rest of RR which would massively complicate second-line servicing at operational units. What evidence is there of ANY change to RR production tolerances? 

As noted above, the 3 RR factories were already pumping out thousands of Merlins per year before the Ford factory got up and running. As we all know, implementing changes mid--stream in any production line is challenging to say the least. To suggest that, in late-1940 or early-1941, RR suddenly changed their tolerance standards without any impact on production seems laughable in the extreme. 

Yes, there are different fit standards. However, I find it equally laughable that a factory producing circa 30,000 engines wasted time searching for the one piston that fits a particular cylinder. That approach is ridiculous, IMHO. To do the same thing when the Glasgow factory got into its swing, and where there wasn't an experienced engineering workforce, is equally laughable.


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## Reluctant Poster (Sep 11, 2022)

tomo pauk said:


> Unfortunately, the sentences (my emphasis):
> _Like Packard, the British Ford factory redrew the RR drawings and *tightened the tolerances* so the engines could be mass produced._
> 
> and:
> ...


I didn't make that post to start the tolerance war again. I fully agree that RR tolerances were the same as Packard's . The point I was trying illustart was Olley's recollections regarding Fords involvement with the Merlin which the article quotes. In no way shape or form would I agree that the Ford engine was the equal of the Merlin. And in no way shape or form would I agree that a Packard built Merlin was a marvel of mass production while the Rolls Royce was a hand job.


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## Snowygrouch (Sep 11, 2022)

Reluctant Poster said:


> I didn't make that post to start the tolerance war again. I fully agree that RR tolerances were the same as Packard's . The point I was trying illustart was Olley's recollections regarding Fords involvement with the Merlin which the article quotes. In no way shape or form would I agree that the Ford engine was the equal of the Merlin. And in no way shape or form would I agree that a Packard built Merlin was a marvel of mass production while the Rolls Royce was a hand job.

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## Shortround6 (Sep 11, 2022)

Without detailed histories of each factory there can be quite a bit of cross over. It could between 1 and 2 years to get a factory from start of production to reaching full production. 

And in some cases it took a fair amount of time to even get to a few hundred engines a month. 

I looked up the S.S. City of Flint and she sank in a storm on Great Lakes on Nov 11th 1940. She was only 500ft from shore and was salvaged and put back in service. NO idea what happened to the machine tools that were aboard. 

Now from wiki we have on GLasgow...........................
"Engines began to leave the production line in November 1940, and by June 1941 monthly output had reached 200, increasing to more than 400 per month by March 1942."

But apparently Glasgow was starting production with parts shipped in from other factories to provide training. A good idea, to get the workers up to speed. 
There was a whole lot of stuff going on at the same time, and while Ford only started construction of the factory buildings in April of 1940 modern factory construction is not a matter of throwing up buildings and seeing where you can stuff the machinery. You figure out how you want the flow of parts from the different depts to go and join together on the assembly lines lines. Once you have the factory floor plan laid out they you build the building. Ford may have been working on the plans for the factory for weeks or months before they broke ground. 

Packard built 4 engines in their first month of production, Sept 1941, they only built 26 in Dec 1941 but in April of 1942 they built 505. Packard had a few advantages, they weren't being bombed for one thing. 

I am not trying to say the US was better, I am saying that there was a lot of overlap between some of the factories and the way they were building engines in 1943/45 might not have been they way there were building them in 1940/41. Off course that goes for quite a few engines.

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## pbehn (Sep 11, 2022)

Shortround6 said:


> Without detailed histories of each factory there can be quite a bit of cross over. It could between 1 and 2 years to get a factory from start of production to reaching full production.
> 
> And in some cases it took a fair amount of time to even get to a few hundred engines a month.
> 
> ...


I found this 






SS City of Flint (1919) - Wikipedia







en.wikipedia.org




In October 1939, _City of Flint_ was carrying a cargo of tractors, grain and fruit to Britain. On 9 October, the German pocket battleship _Deutschland_ seized the _City of Flint_, declaring her cargo to be contraband and the ship a prize of war. A German prize crew was put on board the ship to sail her back to Germany.[13]​[14]​






Malabar (British Steam merchant) - Ships hit by German U-boats during WWII - uboat.net


The U-boat War in World War Two (Kriegsmarine, 1939-1945) and World War One (Kaiserliche Marine, 1914-1918) and the Allied efforts to counter the threat. This section includes over 21.000 Allied Warships and over 11.000 Allied Commanders of WWII, from the US Navy, Royal Navy, Royal Canadian...




uboat.net




At 01.50 hours on 29 Oct 1939, U-34 fired two torpedoes at two steamers and one destroyer in convoy HX-5A about 180 miles west of Lands End and claimed two hits. In fact, only the ship of convoy commodore, the *Malabar* (Master Henry Herbert Armstrong), was hit and sunk. Five crew members were lost. The master, the commodore (Rear Admiral G.W. Taylor, RNR), two naval staff members and 66 crew members were picked up by *HMS Grafton (H 89)* (Cdr M.S. Thomas, RN) and landed at Plymouth.

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## Snowygrouch (Sep 12, 2022)

The RR files I have say that the Merlin 1 engine was never properly tooled up, I.e. it wasn’t mass produced in general principle. So we can see that sometime between then and about 1940/1941, RR was in some transition phase between knocking up a few merins at derby and managing a series of large factories mass producing them.

So the simple answer to the source of this silly myth is that the notion of how RR made engines came from anecdotes from this transitionary period.

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## pbehn (Sep 12, 2022)

Snowygrouch said:


> The RR files I have say that the Merlin 1 engine was never properly tooled up, I.e. it wasn’t mass produced in general principle.  So we can see that sometime between then and about 1940/1941, RR was in some transition phase between knocking up a few merins at derby and managing a series of large factories mass producing them.
> 
> So the simple answer to the source of this silly myth is that the notion of how RR made engines came from anecdotes from this transitionary period.


I read somewhere on the story of the Ford Manchester plant that the first discussions between RR and Ford were with Ford France. The Trafford Park factory in Manchester started work to become a shadow factory in 1938. Mass production is a science and a skill, it would have been foolish of RR NOT to pick the brains of Ford engineers if they had the chance.

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## ThomasP (Sep 12, 2022)

I have alway assumed that the comment/story re Packard tightening up tolerances was referencing the need for Packard to tighten its own tolerances. The tolerances for the Packard automobile engines of the time were not as tight as the tolerances on the Merlin engine.

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## drgondog (Sep 12, 2022)

Shortround6 said:


> Without detailed histories of each factory there can be quite a bit of cross over. It could between 1 and 2 years to get a factory from start of production to reaching full production.
> 
> And in some cases it took a fair amount of time to even get to a few hundred engines a month.
> 
> ...


Totally agree re: New Factory design for specific application. Under any circumstances, Ford would start with the Process Plans for each part, carefully consider the machine tools required to make them, to world class process plan(s) desired for each class of parts. The next consideration is to match as well as possible the flow of parts from one set of machine requirement to the Next and plan for common batteries if possible to minimize movement (and tracking) of parts - with an eye to complete as much of a complex part as possibe in one machining/process center as possible. Quality and throughput time drive costs.

Part classification systems arose in 70s' to aggragate families of parts as designed to combine with processes to provide insight on better planning for throughput. Battery environments such as vehicles are less difficult than bespoke manufacturers that design and build 'common' theme parts in many variations (Wellsite drill tools for example). Airframe companies are notorious for what 'looks like battery' but are more like bespoke because of the complex shapes of machine parts from one aircraft to another - often better served by subcontracting than purchasing five axis mill machines for deep pocket forgings as embedded in F-111 swing wing installations.

One goal of Group Technologies is to match as clsely as possible families of parts with certain design attributes (shaft versus aforementioned swing wing support) to process plans which can be grouped into one concentrated batch of machines - and be completed in that group, thereby eliminating all together the cherished tradiions of parts chasing from one end of the factory to another.

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## drgondog (Sep 12, 2022)

ThomasP said:


> I have alway assumed that the comment/story re Packard tightening up tolerances was referencing the need for Packard to tighten its own tolerances. The tolerances for the Packard automobile engines of the time were not as tight as the tolerances on the Merlin engine.


ThomaP - while I don't discount the possibility that Packard needed to 'tighten' its own tolerances, I don't think it can be based on facts unless access to RR drawings and comparable Packard drawing can be compared.

An industry (American automotive/engine) that thrives on reliability supported by global distribution of interchangeble parts strongly suggests that neither Packard nor Ford needed instruction on tolerances to support that vision?

That said, I don't have that history and knowledge that youand others have of the R-R, Ford and Packard deliberations and outcomes in the engineering dimensional changes to argue the point.


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## ThomasP (Sep 12, 2022)

I do not think it is a case of Packard needing instructions on tolerances so much as it is that the required tolerances for the relatively small in3 and low HP/in3 automobile engines of the time would have been significantly different than for relatively large and high HP/in3 engine like the Merlin/V-1710/DB601/etc.

Using the crankshaft as an example:

As pointed out by Snowygrouch in his post "An interesting read about the Packard built Merlin engine." the Merlin crankshaft tolerance of +/-0.00025" was ~twice as tight as modern crankshaft tolerances for automobile engines. This was an amazingly tight tolerance for 1940, and was presumably a necessary tolerance.

It was not until the early-1990s that holding diameter tolerances of +/-0.00025" became relatively common on machined parts. This was due to a combination of increased capability of modern computer controlled turning and machining centers and the associated reduced cost of achieving the tolerance. Prior to the early-1990s a tolerance of +/-0.0005 was the best commonly achieved. During WWII +/-0.001 was the tightest commonly achievable tolerance.

(A general rule of thumb in machining is that for every time you reduce the tolerance by half you double the time it takes to make that particular feature.)

The cost of a Merlin engine (I think) was somewhere around $6000 in 1941. The cost of the most expensive Packard sedan was ~$5800.

There is no reason to believe that the Packard or Ford automobile engine of 1940 was held to tolerances as tight as modern high performance automobile engines. It would not have been economical or necessary within the industry needs of the time.

I know that if I were approached to manufacture a scaled up engine (such as from a 356 in3 V8 to a 1650 in3 V12) one of the first things to go through my head would be that - due to the size alone - tolerances would have to be tighter in order to achieve the required cumulative runout/ straightness/ flatness (to manage vibration and sealing problems) and to maintain fit/interchangeability of parts.

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## pbehn (Sep 12, 2022)

ThomasP said:


> I do not think it is a case of Packard needing instructions on tolerances so much as it is that the required tolerances for the relatively small in3 and low HP/in3 automobile engines of the time would have been significantly different than for relatively large and high HP/in3 engine like the Merlin/V-1710/DB601/etc.
> 
> Using the crankshaft as an example:
> 
> ...


Tolerances dont always scale up, you have to work to different tolerances or have different ways of doing things.

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## pbehn (Sep 12, 2022)

To further complicate or colour the debate, the RR Trafford Park factory was set up to be near the Vickers Avro Manchester factory, but the Manchester used Vulture engines. Lost in the sands of time are the discussions of what the Trafford Park factory would make Vulture or Merlin, we know when the Vulture was cancelled, but prior to that it must have been increasingly "on the back burner". Also I read that they imported a special precision machine tool from Switzerland for the main bearing journals, the first was lost when a ship was sunk (maybe one of those Callum posted about) so they got another, ordered from the Swiss but shipped via USA due to "hostilities".

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## drgondog (Sep 12, 2022)

ThomasP said:


> I do not think it is a case of Packard needing instructions on tolerances so much as it is that the required tolerances for the relatively small in3 and low HP/in3 automobile engines of the time would have been significantly different than for relatively large and high HP/in3 engine like the Merlin/V-1710/DB601/etc.
> 
> Using the crankshaft as an example:
> 
> As pointed out by Snowygrouch in his post "An interesting read about the Packard built Merlin engine." the Merlin crankshaft tolerance was ~twice as tight as modern crankshaft tolerances for automobile engines. This was an amazingly tight tolerance for 1940, and was presumably a necessary tolerance.


True - but debate between Packard and R-R is simply cut off by R-R in the context "we are the customer, giving you a contract to meet our specifications depend on a.) Willingness to do so, and b.) capability to do so, and c.) adhere to the QA/QC demands contained theerin".


ThomasP said:


> It was not until the early-1990s that holding diameter tolerances of +/-0.00025" became relatively common on machined parts. This was due to a combination of increased capability of modern computer controlled turning and machining centers and the associated reduced cost of achieving the tolerance. Prior to the early-1990s a tolerance of +/-0.0005 was the best commonly achieved. During WWII +/-0.001 was the tightest commonly achievable tolerance.


Not to belabor the point, but didn't Packard deliver the required tolerances required by R-R? As a tangent, the tolerances achieved dimensionally and spherically exceeded that in the 1945-1950 timeframe at Lawrence Livermore, Hanford, Oak Ridge and Savannah River nuclear weapons designs and fabrication. The tolerance issues were achieved by combination of computer controls and polishing techniques. Pause - I know this anecdotally, not by hands on observation. The increased tolerance achivements were requiredto improve efficiency of nuclear chain reactions 


ThomasP said:


> (A general rule of thumb in machining is that for every time you reduce the tolerance by half you double the time it takes to make that particular feature.)
> 
> The cost of a Merlin engine (I think) was somewhere around $6000 in 1941. The cost of the most expensive Packard sedan was ~$5800.


The point is well taken and illustrates the imbedded direct costs and overheads associated with producing the Merlin and the Packard. There is no question that either engine required significantly more investment in machine tools and processes than associated with a Pacakrd (or Ford) vehicle of the 1940s. But recognize that tooling is depreciated from the Balance Sheet while overhead is baked into Indirect Costs - who knows what the unit cost (not price) was unless the books are available in detail. I assume (bad word) that the Packard contract was let as Cost Plus with exquisite details contained in R-R/Packard Agreement


ThomasP said:


> There is no reason to believe that the Packard or Ford automobile engine of 1940 was held to tolerances as tight as modern high performance automobile engines. It would not have been economical or necessary within the industry needs of the time.


Agreed again - but the question being asked is 'Could They', and what extra ordinary steps, if any, would have been required to a.) acquire the tooling, b.) firm up the process plans to machne, inspect and approve the 'extreme' (greater than auto, but within reach technically) tolerances required for criical parts, c.) acquire and install the upgraded tools (i.e including making in-house, d.) train for the upgraded processes and equipment. All this would have led to pricing and contractural framework to be Paid. 


ThomasP said:


> I know that if I were approached to manufacture a scaled up engine (such as from a 356 in3 V8 to a 1650 in3 V12) one of the first things to go through my head would be that - due to the size alone - tolerances would have to be tighter in order to achieve the required cumulative runout/ straightness/ flatness (to manage vibration and sealing problems) and to maintain fit/interchangeability of parts.


Absolutely agreed. I will bow to your hands on experience in the related field, noting that even at Bell Helicopter and Vought and Lockheed were uch considerations and design attributes requiring 'flatness' and 'sphericity' beyond standard manufacturing strike zone.

I was Program Manager for 18 mo for GE contribution to AFCAM and the one customer requiring Q Clearance was mean little prick with last name Rickover - whom I really respect and would have possibly feared had I ever worked in his chain of command. He had a ost interesting approach to make on 'uncomfortable' during his personal interview. If you failed it - you were out - and Nixon couldn't over-ride.

General Dynamcs was a major component of the design and manufacturing corps we looked at. That included all major contractors that specifically had huge investments in tooling ranging from Jeweller's lathes to extreme tolerance capable 5-axis bad boys. There is a story behind this, but the nuclear sub business (and associated Contractors located in CA and WA and N and SC) were a major focus.

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## ThomasP (Sep 12, 2022)

I am not saying in anyway that Packard or Ford were not able to meet the specifications. I am only addressing the possible origin of the statement(s) (I have read accounts of the statement as coming from the Ford rep or the Packard rep) that 'they would have to tighten the tolerances for mass production'. Such a statement would make sense if it was addressing a need for Packard or Ford to adopt tighter tolerances than they usually used for their mass produced automobile engines. It would not make any sense otherwise.

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## pbehn (Sep 12, 2022)

ThomasP said:


> I am not saying in anyway that Packard or Ford were not able to meet the specifications. I am only addressing the possible origin of the statement(s) (I have read accounts of the statement as coming from the Ford rep or the Packard rep) that 'they would have to tighten the tolerances for mass production'. Such a statement would make sense if it was addressing a need for Packard or Ford to adopt tighter tolerances than they usually used for their mass produced automobile engines. It would not make any sense otherwise.


I think you are getting the wrong end of the discussion. The whole "thing" stems from a discussion between Cyril Lovesey of RR and someone from Ford in the early days of Ford being involved in RR production. To paraphrase the guy from Ford said "we cannot manufacture to these tolerances" to which Lovesey replied, are they too demanding" the Ford guy said "no, to make car engines we use much tighter tolerances because every piston has to fit in every cylinder". However at the time Lovesey had no experience of production engineering, his main work was on the racing engines, where you probably do machine the bores and then machine pistons to fit.

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## Reluctant Poster (Sep 12, 2022)

FLYBOYJ said:


> $500,000 in 1938 dollars is well over 10 million in today's dollars and even though GM was a large corporation back then, this was a depression era and no big corporation was going to make an investment like this unless they are going to get a return. The individual(s) responsible for the business sector behind something like this would probably lose his/ their job(s) and wreck his/their career if this investment wasn't profitable. Just ask Alexander P. de Seversky.
> 
> In the bigger picture, once again you miss the fact that large *aircraft companies* normally do not risk development of a technology unless they know they have a contract in hand or they are pretty certain they can sell their product at a later date. You can't compare the manufacture of diesel engines, automatic transmissions or any other automotive products to the aviation industry of the late 1930s, especially when technology was continually expanding and the future was so uncertain.


I admit I got a little down into the weeds but the point I was trying to make was that GM was investing very large sums of money in all sorts of things (appliances, air conditioning, leaded gasoline) in the 20s and 30s and they continued to do so even in the depression. For example, they bought Opel for 33.36 million in 1931 and built a new factory for it as well. Other examples include buying Vauxhall and Holden and launching a new truck brand in the UK (Bedford).
Perhaps a better way to state my case was that GM became a billion-dollar corporation in terms of market valuation in 1926. In 1929 they were neck and neck with Standard Oil (New Jersy) for the title of world largest corporation with a revenue of $1.5 billion. Obviously, those numbers dropped over the next few years, but GM was always profitable throughout the depression. Even if you cut that revenue in half the $500,000 still qualifies as petty cash to a company the size of GM. What I draw from all this is that GM had little faith in Allison. That is why I asked how much GM invested in North American. The move from the east coast to California and the establishment of a new factory was not driven by military contracts and must have been paid for by GM.


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## ThomasP (Sep 12, 2022)

Hey pbehn,

By the time that discussion took place (1940?), several thousand Merlins had been produced. By that point in time RR and associates would have sorted out the process such that at least 90% of the pistons and 90% of the cylinder bores would meet full interchangeability standards, and probably more like 95% and 95% - at least in terms of machined dimensions. The casting weights might have tossed a problem into the mix, such that the pistons might have been sorted by weight? I have seen Merlin pistons that were machined into weight specifications by removing material from the inside-bottom of the casting but I do not know if this was the normal method during the war, or if they were supplied in matched sets.


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## FLYBOYJ (Sep 12, 2022)

Reluctant Poster said:


> I admit I got a little down into the weeds but the point I was trying to make was that GM was investing very large sums of money in all sorts of things (appliances, air conditioning, leaded gasoline) in the 20s and 30s and they continued to do so even in the depression. For example, they bought Opel for 33.36 million in 1931 and built a new factory for it as well. Other examples include buying Vauxhall and Holden and launching a new truck brand in the UK (Bedford).
> Perhaps a better way to state my case was that GM became a billion-dollar corporation in terms of market valuation in 1926. In 1929 they were neck and neck with Standard Oil (New Jersy) for the title of world largest corporation with a revenue of $1.5 billion. Obviously, those numbers dropped over the next few years, but GM was always profitable throughout the depression. Even if you cut that revenue in half the $500,000 still qualifies as petty cash to a company the size of GM. What I draw from all this is that GM had little faith in Allison. That is why I asked how much GM invested in North American. The move from the east coast to California and the establishment of a new factory was not driven by military contracts and must have been paid for by GM.


And despite the size of GM (per your numbers which I wont dispute) $500,000 in the late 30s is about 12 million in today's dollars. I don't know if you actually worked in the aviation manufacturing industry, but I seen managers canned for not making profit margins, let alone losing a fraction of that amount.


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## Thumpalumpacus (Sep 12, 2022)

ThomasP said:


> I do not think it is a case of Packard needing instructions on tolerances so much as it is that the required tolerances for the relatively small in3 and low HP/in3 automobile engines of the time would have been significantly different than for relatively large and high HP/in3 engine like the Merlin/V-1710/DB601/etc.
> 
> Using the crankshaft as an example:
> 
> ...



Posts like this are why I love this forum. There's so much to learn!

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## pbehn (Sep 12, 2022)

ThomasP said:


> Hey pbehn,
> 
> By the time that discussion took place (1940?), several thousand Merlins had been produced. By that point in time RR and associates would have sorted out the process such that at least 90% of the pistons and 90% of the cylinder bores would meet full interchangeability standards, and probably more like 95% and 95% - at least in terms of machined dimensions. The casting weights might have tossed a problem into the mix, such that the pistons might have been sorted by weight? I have seen Merlin pistons that were machined into weight specifications by removing material from the inside-bottom of the casting but I do not know if this was the normal method during the war, or if they were supplied in matched sets.


I dont think it is stated when the discussion took place because it makes a better story if it isnt, it also isnt stated that the discussion was with Ford not Packard. By 1940 RR were already mass producing Merlins in Crewe and the Manchester and Glasgow factories were either in production or tooling up. My guess is the discussion was much earlier, when Ford were first starting to work on the Trafford Park factory so 1938-39.

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## drgondog (Sep 13, 2022)

Reluctant Poster said:


> I admit I got a little down into the weeds but the point I was trying to make was that GM was investing very large sums of money in all sorts of things (appliances, air conditioning, leaded gasoline) in the 20s and 30s and they continued to do so even in the depression. For example, they bought Opel for 33.36 million in 1931 and built a new factory for it as well. Other examples include buying Vauxhall and Holden and launching a new truck brand in the UK (Bedford).
> Perhaps a better way to state my case was that GM became a billion-dollar corporation in terms of market valuation in 1926. In 1929 they were neck and neck with Standard Oil (New Jersy) for the title of world largest corporation with a revenue of $1.5 billion. Obviously, those numbers dropped over the next few years, but GM was always profitable throughout the depression. Even if you cut that revenue in half the $500,000 still qualifies as petty cash to a company the size of GM. What I draw from all this is that GM had little faith in Allison. That is why I asked how much GM invested in North American. The move from the east coast to California and the establishment of a new factory was not driven by military contracts and must have been paid for by GM.


Actually the move from Dundalk MD to Inglewood Was driven by the BT-9 and then the BC-1 follow up funded the primary expansion at Mines Field, Inglewood. Just prior to that NAA got its foot into the AAC world with the XO-47 (Kindelberer/Schmued design). 

GMC bought NAA in 1928, then bought Fokker Aircraft and formed GMAC to operateboth NAA and Fokker - then acquired Berliner-Joyce Aircraft. After the Knute Rockne crash in a Fokker F-10 in 1931, the Teterboro plant was closed and remaining folks moved to Berline-Joyce plant at Baltimore airport and Dundalk, MD. About this time, the GMC Board exec Ernie Breech hired Kindelberger. The YO-47 contract was let as the first external contract award obtained by NAA.

GMC funded $125,000 toward General Order GA-15 (XO-47) for competition in the three seat observation competiion. Shortly afterwards GMAC took the name North American Aviation.

When NAA decided to compete for the two seat monoplane trainer, (future BT-9), GMC invested another $16,000 for the NA-16 proposal effort. I believe that GMC might have financed several loans related to production assets after that but have found no records to substantiate.

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## Shortround6 (Sep 13, 2022)

The contract/s for the 0-47 involved 239 aircraft. The last contract was for 74 aircraft placed in 1938 so NA was either making money or repaying loans. 
Please note that Curtiss only got orders for 215 P-36s from the US government (and about 700 export orders) So NA was doing pretty well compared to other US Airplane makers. 
Everybody had eyes on the future. 
GM's problem with Allison was that until the order came for the P40 engines Allison was pretty small potatoes in the engine field. 
In 1938 they delivered 12 engines, in 1939 they delivered 48 ( for YP-37s, Airacudas and prototypes)
Wright built 1800 R-1820s in 1938, not counting the smaller Whirlwinds (249) and 33 about R-2600s 
P & W built 695 R-1830s in 1938 and was building R-985s, R-1340s, R-1535s, R-1690s. They had been working on the R-2800 since 1936. 
The US Airlines and commercial aviation showed no real interest in liquid cooled engines and the Navy, once airships were gone, were only showing polite interest. (just making sure they didn't miss something) but that left the Army as pretty much the only customer and the Army had their own oar in the water with the Continental hyper engine (largely designed by Army officers/employees) . And Lycoming was chasing the same market. 

GM In other areas could see a way to dominate a market or at least be a major player. It was one thing to loose money in the short term to reach a new market or to create a new market. But the market was looking pretty iffy over the winter of 1938-39 for Allison. Wright and P & W were getting overseas sales in huge quantities. 
Allison had no real production facilities.

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## special ed (Sep 13, 2022)

If I may throw some auto data into this mix, Packard was a high end builder. There were no cheap Packards. Their competition was Cadillac (GMC),Lincoln (Ford), Pierce Arrow and some semi-custom companies such as Duesenberg and Auburn. Packard top engine in 1939 was their V-12 of 473 cubic inches. Packard engines were well built and reliable with close tolerances in the automotive world. They were the most logical choice to build Merlins.


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## SaparotRob (Sep 13, 2022)

special ed said:


> If I may throw some auto data into this mix, Packard was a high end builder. There were no cheap Packards. Their competition was Cadillac (GMC),Lincoln (Ford), Pierce Arrow and some semi-custom companies such as Duesenberg and Auburn. Packard top engine in 1939 was their V-12 of 473 cubic inches. Packard engines were well built and reliable with close tolerances in the automotive world. They were the most logical choice to build Merlins.


“Ask the man who owns one.“


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## Shortround6 (Sep 13, 2022)

The is just a lot of confusion about the Merlin "tolerance" saga. In part because nobody now knows (unless they have access to the written records) what tolerances anybody is talking about. 
I have have an old book with some tolerances for a Merlin II with as built tolerances and allowable wear before rebuild. 
What is not given was the allowable production tolerances. 

For instance the permissible weight difference for for the pistons fitted/selected to one engine was 1/2 oz. 
The Permissible variation in weight between any two pairs of rods, pistons, pins fitted to one engine was 1 oz. 

Maybe you could fit a heavy piston on a light rod?
In any case this seems like a pretty tight specification. but it does not tell us at what point a piston was too light or too heavy to be sent from the inspection area to the assembly area (and they sure did NOT go from a the machinery area to assembly without stopping at inspection). 
There seems to have been a degree of selection on pistons and rods as far as weight went. 

Some of the tolerances are very tight on this Merlin II engine. I doubt that Ford was making any money building car engines to these tolerances. 

But RR was NOT trying to make parts that would interchange between every engine. Ford could do that in part because a Ford car engine was operating at much less pressure in the cylinders and much lower stresses in the parts and block. 
I don't have the tolerances of the cylinder bore but the Pistons were supposed to be oval?


Diameter of piston at top measured in the axis of the gudgeon pin.............................................5.36650 max/5.34450min
Diameter of piston at top measured at right angels to the axis of the gudgeon pin..............5.370 max/ 5.368 min
Diameter of piston at bottom measured in the axis of the gudgeon pin.....................................5.372 max/5.370 min.......................................max permissible wear 5.560
Diameter of piston at bottom measured at right angels to the axis of the gudgeon pin......5.380 max/5.378 min........................................max permissible wear 5.570

This does not sound like sloppy tolerances as fitted to me?

Crankshafts were allowed two regrinds in service. 
The journals were supposed to be.................. 3.349/3.34850.........................................permissible worn.................................3.347
1st regrind.................................................................3.344/3.34350
2nd regrind...............................................................3.339/3.33850

Perhaps there were other parts that had greater tolerance. 
But again, this was as fitted, Not as "manufactured."

I am not seeing a room for sloppiness but we are not looking at final assembly _procedures_. 

Was some of this stuff built oversized and "polished" to fit ? (forget the file nonsense) 
This may have been a long standing practice and in small scale production it might have reduced scrape. 
It is hard to salvage a too small part. 
But in large scale production the time needed to correct too many large parts outweighs the benefits of not tossing out the bottom of the tolerance range.

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## GregP (Sep 13, 2022)

Shortround6 said:


> The is just a lot of confusion about the Merlin "tolerance" saga. In part because nobody now knows (unless they have access to the written records) what tolerances anybody is talking about.
> I have have an old book with some tolerances for a Merlin II with as built tolerances and allowable wear before rebuild.
> What is not given was the allowable production tolerances.
> 
> ...



As far as the Allison goes, there were only three acceptable sets of pistons: nominal, .010 over, and .020 over. The pistons could be a bit on the sloppy side, but the rings could not. Rings were specified at an end gap.

The shape of the pistons is almost irrelevant. They are what they are so the metal expansion at operating temperature makes the pistons about round. The accuracy of fit is almost entirely dependent on the piston rings, 5 sets of rings for each piston on an Allison V-1710. If you check the Table of Fits on an Allison V-1710, there are 5 piston rings.


The top ring in groove has an end gap of .0025" -.0040." That's a total tolerance of .0015".
The second ring in the groove has the same tolerance.
The third and fourth rings in groove has a tolerance of .002" - .0035". Again, a total tolerance of .0015."
The 5th​ ring in groove has a tolerance of .001" - .0025".Again, a total tolerance of .0015".
For you metric guys, 0.0015" is 0.0254 mm, so the tolerance of the ring end gaps is basically .0381 mm. That ain't too shabby for accuracy in mid-WWII.



In a Merlin II, the ring end gap tolerances are .025 - .030" with permissible gap after wear at 0.085", per piston and connecting rods fits and clearances, (Figure 64), Merlin Manual dated late 1938. So, the Allison E-series engine actually had a tighter end gap clearance than a Merlin II, but the Allison E-series was a later engine than a 1938 Merlin II. A comparable Merlin may have had clearances similar to the Allison, and very likely did.


Packard auto engine V-12 crankshaft clearances were .005" - .0025", so you're looking at a total tolerance of .0025", or about 0.00635 mm. I don't have the piston ring gap clearances for a Packard V-12 AUTO engine, but they are pretty decent.

The entire tolerance issue for Merlins revolves around Packard wanting to engineer the Merlin for replacement parts being interchangeable and not for fitting a part to an engine. When a Packard Merlin is running right, it makes almost exactly the same power as a Rolls-Royce Merlin running right, within acceptable tolerances between "identical" engines. But the Packard Merlin is a bit easier to overhaul because it requires less "fitting." Later RR Merlins had more interchangeable parts anyway, and less "fitting."

That comes for current warbird owners running Merlins. Most people in the U.S.A. are running Packard Merlins because we can find parts for them easier. I'd bet most European owners run Rolls Royce Merlins for the same reason, but you can find both types in both places, with happy owners. I don't know of ANY owners who claim their Merlin brand runs better than the other one. Both seem to run just fine when things are operating correctly.

I HAVE seen two P-51s that, when flying side by side, one requires 2" more MAP to fly formation. But that isn't an engine thing, it's a airframe fit issue. If you swap the two Merlins the draggier airframe STILL requires 2" more MAP than the other airframe. Both are P-51Ds! Individual airframe DID have tolerances for speed and engine power.Some were FAST and some were just a bit slower. But, they all could cruise within a small gap of fuel consumption.


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## ThomasP (Sep 13, 2022)

!. I do not think that anyone has said that a RR Merlin is better than a Packard Merlin?

2. The tolerances for the Merlin crankshaft, pistons, etc, would have been figured out and specified prior to the prints being handed over to Ford or Packard, with said tolerances allowing ~100% interchangeability of parts. To have any other method would have required all of the people in charge of RR engineering and manufacturing to be buffoons.

3. The only reason there would have been any 'fitting' or selection of particular parts would have been if the parts were not made to the specification. The effects of any specific failure to meet specification would have applied to Ford and Packard as much as for RR.

4. Did Ford and Packard have a lower percentage of out of specification parts coming off the production line than RR? is not a question I can answer. However, the only quality difference there would have been, whether for universal interchangeability or in terms of sets, would have been due to the quality of workmanship based on the machinery used, the skill of the workers, and the time allowed to manufacture the parts - none of of the difference would have been due to the RR blueprint specs. Some out of spec parts would have been used anyway - with the awareness and acceptance of potential problems among the responsible agencies. In this case there would sometimes have been a requirement for 'fitting' and/or rework in one form or another. RR, Ford, and Packard, would all have had significant numbers of parts that fell into this category. Unless Ford and Packard discarded all of the parts that did not meet initial spec, there would have been 'fitting' and/or rework going on at the Ford and Packard factories also.

5. Depending on what type of system (ie room air conditioner or space shuttle environmental control module) and the quality control requirements for the parts (ie 90% of the room air conditioners have to achieve a 5 year life vs the space shuttle environmental control module requiring a 0% failure rate for 1 mission) the same factors may come into play today as in WWII.

In todays machine shops, small numbers of parts that are initially out of spec are usually sent to a tool room for rework (if possible) to allow the parts to meet spec. If the numbers are large there may be special manufacturing lines set up. Sometimes the parts can not be made to meet spec, in which case a request for variance may be sent to the responsible agency. Sometimes the request comes back with an OK to ship as is. Sometimes it will be OK to ship as long as the parts are labeled/tracked correctly. Sometimes the parts are given a different category, such as to be issued in emergencies only.

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## wuzak (Sep 14, 2022)

GregP said:


> The entire tolerance issue FOR mERLINS revolves around Packard wanting to engineer the Merlin for replacement parts being interchangeable and not for fitting a part to an engine. When a Packard Merlin is running right, it makes almost exactly the same power as a Rolls-Royce Merlin running right, within acceptable tolerances between "identical" engines. But the Packard Merlin is a bit easier to overhaul because it requires less "fitting." Later RR Merlins had more interchangeable parts anyway, and less "fitting."



Isn't that just another variation of the myth?

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## PAT303 (Sep 14, 2022)

GregP said:


> But the Packard Merlin is a bit easier to overhaul because it requires less "fitting." Later RR Merlins had more interchangeable parts anyway, and less "fitting.


Before the 60 series RR was developing the Merlin at an alarming rate so mass production was not an option, I have no doubt the earliest Merlin III-XII and XX needed extra work fitting parts from various contractors but once the 60 series became the engine of choice standardisation could commence.


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## GregP (Sep 14, 2022)

ThomasP said:


> !. I do not think that anyone has said that a RR Merlin is better than a Packard Merlin?
> 
> 2. The tolerances for the Merlin crankshaft, pistons, etc, would have been figured out and specified prior to the prints being handed over to Ford or Packard, with said tolerances allowing ~100% interchangeability of parts. To have any other method would have required all of the people in charge of RR engineering and manufacturing to be buffoons.
> 
> ...



Apparently, you've never rebuilt a Merlin. There are several things that require "fitting" on ANY Merlin.

One such item is the valve seats. On a Merlin, you have to unscrew the old valve seats and torque in the new ones and, once at the proper torque, the seat snaps off. It's supposed to be at the right height, but is often off by a bit.

Merlin head bolts must be torqued every 25 hours!

On an Allison, you torque the heads during assembly and never have to touch them again. A Merlin has about 11,500 parts. An Allison has about 7,000 parts. Why use 8 screws when 25 will work just as well?

There is a nice long list of ways the Merlin could have been improved upon as far as servicing and assembly goes, but the engine serves VERY well as-is. Still, there is no reason why some things had to be done the way they were done, and the Allison COULD have been a great performer had there been a concentrated effort to make that happen. Alas, in the real world, the integral 2-stage unit was never developed.

The title of this thread can be answered with a simple "Yes." It would have required development of an integral 2-stage supercharger, but that was never approved nor funded by the U.S. government. So, reality being what it is, that unit was never developed. The fact that it COULD HAVE BEEN developed is a "what if," but the integral 2-stage unit was developed for the Merlin, and there is no technical reason why it could NOT have been so developed for the Allison.

The Allison had many things to recommend it. It was much easier to assemble, held a tune longer, and was more rugged than a Merlin.

That being said, the Merlin was and is a superb engine with performance to wish for and a few characteristics you had to live with if you wanted that performance. History tells us the Merlin was EXCELLENT, and I have no intention of saying otherwise. If I had a warbird, I'd be very pleased to fly either engine. If I had a choice, I'd opt for a Merlin-powered bird simply because I love some of the birds powered by the Merlin.

My first choice would be a Spitfire Mk IX but a P-51D/K would serve quite nicely.

Edit: I'd avoid a radial-powered bird simply because I don't have a 25-year old curvy girlfriend to help wipe off all the oil.

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## GregP (Sep 14, 2022)

wuzak said:


> Isn't that just another variation of the myth?



No, according to owners.

I believe the owners. I am acquainted with several, me not being one, unfortunately.


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## Shortround6 (Sep 14, 2022)

The Merlin, as already mentioned, was evolving considerably. 
And the British had ideas to improve it which they couldn't always incorporate due to the need to produce what they were already making rather the introduce the "improvements". 

The Packard V-1650-1 is part of this. What Packard initially got were the drawings and sample engine/s for the Merlin XX engine. However RR had already designed a the two piece block while Packard was tooling up and it was decided that Packard would got into production first with the two piece block as it wasn't going to delay Packard production to change the block design. Why tool up for the old design? The British factories did change over later. 

Packard used the Bendix carburetor mainly because that was standard US practice. NO American engine maker used their own carburetor. From Wright and P & W down to Continental and Lycoming, American engine makers pretty much bought the carbs for specialty carb makers. Packard found a Carb from Bendix that would work and if it needed different mounting holes or something else they modified the engine to suit rather than build their own carburetor shop to copy the British carbs or Bendix supplied the carb with flanges and bolt holes to suit the locations to the Merlin engine. 

A later Allison was rather different than an early (1940) Allison and late Merlin's were different than early Merlins.

Both got longer lasting while making more power. 

Packard built 13 marks of Merlins for the British and V-1650s run from the -1 through the -25 (all odd numbers but not all built) by the time the P-82 saga ends. 

There was room for a fair degree of overlap.

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## GregP (Sep 14, 2022)

Shortround6 said:


> The Merlin, as already mentioned, was evolving considerably.
> And the British had ideas to improve it which they couldn't always incorporate due to the need to produce what they were already making rather the introduce the "improvements".
> 
> The Packard V-1650-1 is part of this. What Packard initially got were the drawings and sample engine/s for the Merlin XX engine. However RR had already designed a the two piece block while Packard was tooling up and it was decided that Packard would got into production first with the two piece block as it wasn't going to delay Packard production to change the block design. Why tool up for the old design? The British factories did change over later.
> ...



Well said.


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## PAT303 (Sep 15, 2022)

GregP said:


> Merlin head bolts must be torqued every 25 hours!


I'd like to know the reason for that, very early engines with copper style HG needed the bolts torqued down then have the engine run up to temp and torqued a second time once cooled, I don't know why torqued bolts needed to be re-torqued over and over.


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## ThomasP (Sep 15, 2022)

Hey GregP,

re "One such item is the valve seats. On a Merlin, you have to unscrew the old valve seats and torque in the new ones and, once at the proper torque, the seat snaps off. It's supposed to be at the right height, but is often off by a bit." and "Merlin head bolts must be torqued every 25 hours!"

I have primarily been addressing the idea that the tolerances had to be tightened by Ford or Packard to aid in production. Your examples are a matter of design/assembly/maintenance procedures, and do not address the myth involving the tolerances.

Were the valve seats not torqued down and then 'fitted' in the same manner on the Ford or Packard built Merlins?


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## FLYBOYJ (Sep 15, 2022)

PAT303 said:


> I'd like to know the reason for that, very early engines with copper style HG needed the bolts torqued down then have the engine run up to temp and torqued a second time once cooled, I don't know why torqued bolts needed to be re-torqued over and over.


There are many aircraft (especially helicopters) that have continual torque requirements that are set by the manufacturer, engine and airframe

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## Thumpalumpacus (Sep 15, 2022)

Everything loosens under vibration, doesn't it?


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## wuzak (Sep 15, 2022)

GregP said:


> Apparently, you've never rebuilt a Merlin. There are several things that require "fitting" on ANY Merlin.
> 
> One such item is the valve seats. On a Merlin, you have to unscrew the old valve seats and torque in the new ones and, once at the proper torque, the seat snaps off. It's supposed to be at the right height, but is often off by a bit.



Given that in this day and age the owners are using old parts, reconditioned parts, or re-manufactured parts and are essentially hand building the engine, I would think that more "fitting" is involved now than in the factory in period.


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## Reluctant Poster (Sep 15, 2022)

As I stated previously, I did not intend to start the RR vs Packard debate again. I was drawing (I thought) attention to Maurice Olley's recollection of events regarding Merlin and Ford.

A few facts.

Rolls Royce produced more Merlins than Ford and Packard COMBINED.

Rolls Royce produced 1411 Kestrels in 1936. 1937 saw a changeover from Kestrels to Merlins. I have compiled the following Merlin production table from various sources. Rolls Royce had produced ~24,000 Merlins by the end of 1941 while Ford and Packard had barely got started. As I have posted previously, the Merlin was the second most produced aircraft engine at that time, more than the much vaunted Liberty which was produced by 5 manufacturers and only exceeded by the Hispano V8s.

As can be clearly seen Rolls Royce was in full mass production well before Ford and Packard.

Rolls Royce increased their production by a factor of 10 in an incredibly short time. A magnificent achievement. It should be obvious that they did so by mass production methods.







The myth that Packard (or Ford) made a silk purse out of a sow's ear dos not withstand scrutiny and should be consigned with all the other fairy tales.

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## Geoffrey Sinclair (Sep 15, 2022)

FLYBOYJ said:


> And despite the size of GM (per your numbers which I wont dispute) $500,000 in the late 30s is about 12 million in today's dollars. I don't know if you actually worked in the aviation manufacturing industry, but I seen managers canned for not making profit margins, let alone losing a fraction of that amount.


I can see GM allocating $500,000 to Allison in the second half of the 1930's given what it was going in Australia, putting in about half that amount to start Australian aircraft manufacture from basically scratch in October 1936 on the promise of an order, which took until April 1938 to be signed and then was for a whole 40 trainers.

In 1934, after a DC-2 came second (but first on handicap) in the Britain Australia Air Race, the RAAF Chief of Staff and the Minister of Defence separately asked General Motors in Australia (GMH or General Motors-Holden) whether there was any interest in building the DC-2 in Australia, but GM had sold out of Douglas. 

In early 1935 a proposal was put to build aircraft and their engines in Australia, the Commonwealth Government convened conferences as well as industry undertaking discussions including using a Government appeal for such a company to convince shareholders to put together a local manufacturing syndicate with the funds and expertise. GM was one of 3 companies that in 1935 contributed 12,000 pounds each, about 48,000 dollars to start things, like sending a mission around the world to see what designs were available. Assurances were needed about tariffs and access to facilities, and recording the government promises. Military and civilian aircraft were to be made in that order and exports were also mentioned both airframes and engines to be locally made, plus a factory complex needed to be built.

As Australia was assembling motor vehicles, not making them, this was a major step up in manufacturing capacity, given at the end of 1930's when the ex WWI imperial gift aircraft required overhauls (many had been stored in tents with dirt floors) Australian industry lacked the capacity nor had the interest in acquiring the capacity to do the work. Not without lots more aircraft to work on. As of 1 January 1935 the RAAF had 69 aircraft, plus 28 on order or in storage. A mid 1930's contract for overhaul of Moth and Wapiti wings received 1 high price reply, admittedly the wings had to be repaired in Victoria, not shipped interstate, which cut the possible numbers of replies.

The long term aim was complete manufacture of aircraft by Australia using mostly Australian raw materials. In February 1936 Wing Commander L.J. Wackett, Squadron Leader H.C. Harrison (technical man) and Squadron Leader Murphy, RAAF Chief Workshop Operator were sent on a 5 month tour to visit overseas aircraft industries to determine what design to manufacture. Italy, France, Germany, Czechoslovakia, Holland, Britain and the United States were visited.

The framework being it was expected it would take 5 years from industry initiation before manufacture of a first line defence aircraft could be made (under peacetime conditions), so it was best to start with a simpler design that would a) use Australian raw materials, b) establish manufacture that would be applicable to other aircraft types, c) achieve being able to manufacture a range of aircraft types as quickly as possible, d) introducing designs that would lend themselves to good jigging and tooling so in an emergency production of larger quantities could be carried out by semi skilled labour. A radial engine was preferred as easier to build.

The first design should use as much steel as possible given 1936 Australia had plenty of steel but lacked reliable supply of non ferrous alloys, aluminium and magnesium. The design should be made by regular workshop personnel given the wartime need to significantly increase output. The design should incorporate features likely to be standard practice for some time, a) stressed skin wing and construction, b) all metal construction, c) low wing monoplane type, d) retractable undercarriage, e) variable pitch propeller.

The result was the choice of the North American design, British types of better performance in terms of defence capabilities had not been successfully and easily produced in quantities. The British offered the Fairey Battle light bomber (production started in May 1937) and the Westland Lysander Army Co-operation aircraft (production began in May 1938). The North American design first production, as the BT-9, was in July 1936. The single row Wasp engine it used of around 500 HP could be turned into a 1,000 HP twin Wasp with some redesign but built using the same machine tools and fixtures.

In September 1936 the Australian government told the British what was going to be built. The Commonwealth Aircraft Corporation formed on 17 October 1936, taking over the Tugan company along with its personnel and building a new factory in Melbourne on Victorian Government land. Essington Lewis was Chairman of the company and Lawrence Wackett was appointed Manager. The authorised capital was £1,000,000 paid up to £600,000. The shareholders were 

Broken Hill Proprietary Company Ltd £200,000
Broken Hill Associated Smelters Pty Ltd £150,000
Imperial Chemical Industries of Australia and New Zealand £90,000
General Motors-Holden's Ltd £60,000 (Around US $240,000)
The Electrolytic Zinc Company of Australasia Pty Ltd £50,000
Orient Steam Navigation Company Ltd £50,000.

GM was originally going to have 25% of the company, that was wound back to 16 then 10%, given the politics of British is Best, with ideas like GM was really there to acquire knowledge of the inevitably superior British designs and engineering or it was there to force the purchase of the North American design. Offers to British firms to replace GM were made, they were ignored or replies were along the lines of "only if you build our designs".

In January 1937 the government indicated it would order the North American design as the Wirraway, subject to the usual contract negotiations being successful. Construction of the Melbourne factory began in April 1937 and the initial buildings were ready for occupation in September, further expansions occurred pre war, a near doubling of the floor space. An example of the fixed undercarriage version of the design arrived in Australia in August 1937, one with retractable undercarriage in September. An order for 40 Wirraway including engines was approved in January 1938 and the contract signed in April 1938, the Wirraway name made public on 6 April 1938, the first engine was built in January 1939, the first Wirraway flight on 27 March 1939, official delivery in July, by end July 8 engines had been officially produced, by the end of 1939, 33 Wirraway and 36 engines. 

A lot of money spent before any order and the size of the order was too small to recoup the investment, though an order for an extra 60 Wirraway was approved in September 1938, plus an order for 2 prototypes for a CAC designed trainer in October. The original GM shareholding was controversial and the outcry increased when the Wirraway was chosen, plenty of chances for and pressure on GM to sell their holding. And while the RAAF was becoming increasingly concerned about deliveries of aircraft ordered from Britain as the 1930's went on it was mainly confined to combat types, not trainers. Then in mid 1939 a new wholly public owned operation, the Government Aircraft Factory, was set up to manufacture the first combat type, the Beaufort rather than contract CAC to build it, with part of the reasons for doing so the GM holding in CAC.

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## PAT303 (Sep 15, 2022)

ThomasP said:


> Were the valve seats not torqued down and then 'fitted' in the same manner on the Ford or Packard built Merlins?


Also lapped?


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## Reluctant Poster (Sep 15, 2022)

special ed said:


> If I may throw some auto data into this mix, Packard was a high end builder. There were no cheap Packards. Their competition was Cadillac (GMC),Lincoln (Ford), Pierce Arrow and some semi-custom companies such as Duesenberg and Auburn. Packard top engine in 1939 was their V-12 of 473 cubic inches. Packard engines were well built and reliable with close tolerances in the automotive world. They were the most logical choice to build Merlins.


Not quite Packard was moving into Buick territory in the late 30s. See my previous post.
Post in thread 'An interesting read about the Packard built Merlin engine.' An interesting read about the Packard built Merlin engine.


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## FLYBOYJ (Sep 15, 2022)

Geoffrey Sinclair said:


> I can see GM allocating $500,000 to Allison in the second half of the 1930's given what it was going in Australia, putting in about half that amount to start Australian aircraft manufacture from basically scratch in October 1936 on the promise of an order, which took until April 1938 to be signed and then was for a whole 40 trainers.


But did they?


Geoffrey Sinclair said:


> In 1934, after a DC-2 came second (but first on handicap) in the Britain Australia Air Race, the RAAF Chief of Staff and the Minister of Defence separately asked General Motors in Australia (GMH or General Motors-Holden) whether there was any interest in building the DC-2 in Australia, but GM had sold out of Douglas.
> 
> In early 1935 a proposal was put to build aircraft and their engines in Australia, the Commonwealth Government convened conferences as well as industry undertaking discussions including using a Government appeal for such a company to convince shareholders to put together a local manufacturing syndicate with the funds and expertise. GM was one of 3 companies that in 1935 contributed 12,000 pounds each, about 48,000 dollars to start things, like sending a mission around the world to see what designs were available. Assurances were needed about tariffs and access to facilities, and recording the government promises. Military and civilian aircraft were to be made in that order and exports were also mentioned both airframes and engines to be locally made, plus a factory complex needed to be built.
> 
> ...


Good information but I don't see how this is relevant to the original comment


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## GregP (Sep 15, 2022)

PAT303 said:


> I'd like to know the reason for that, very early engines with copper style HG needed the bolts torqued down then have the engine run up to temp and torqued a second time once cooled, I don't know why torqued bolts needed to be re-torqued over and over.



The reason for that is it is called out in the in-service manual. I didn't write it, but have seen it done and participated in doing it on several Merlins, all of which were in P-51Ds. 

I knew one guy with a Spitfire, but he didn't let anyone else touch it unless they were part of his engine crew. I don't blame him at all.

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## GregP (Sep 15, 2022)

wuzak said:


> Given that in this day and age the owners are using old parts, reconditioned parts, or re-manufactured parts and are essentially hand building the engine, I would think that more "fitting" is involved now than in the factory in period.



Very likely.


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## GregP (Sep 15, 2022)

Reluctant Poster said:


> As I stated previously, I did not intend to start the RR vs Packard debate again. I was drawing (I thought) attention to Maurice Olley's recollection of events regarding Merlin and Ford.
> 
> A few facts.
> 
> ...



I've never heard ANYONE say Packard made a "silk purse of a sow's ear" when it comes to the Merlin.

I HAVE heard that Packard had to work with Rolls Royce on tolerances such that all parts were interchangeable. There's a BIG difference. Packard's Merlins were made with British fasteners and made to British specs. Rolls-Royce Merlins run very well and are not "better" or "worse" than a Packard Merlin. Equivalent models are just that, equivalent.

Don't make this any more sensational than it is. Rolls-Royce made Merlins. Packard and Ford made Merlins. If it were mine, I would prefer a Packard or Rolls Royce Merlin, in no particular order, to a Ford Merlin, but all were good-running engines.

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## Frog (Sep 15, 2022)

Just my 2 c, Continental manufactured Merlins too.

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## Shortround6 (Sep 15, 2022)

GregP said:


> I've never hear ANYONE say Packard made a "silk purse of a sow's ear" when it comes to the Merlin.
> 
> I HAVE heard that Packard had to work with Rolls Royce on tolerances such that all parts were interchangeable. There's a BIG difference. Packard's Merlins were made with British fasteners and mader to British specs. Rolls-Royce Merlins run very well and are not "better" or "worse" than a Packard Merlin. Equivalent models are just that, equivalent.
> 
> Don't make this any more sensational than it is. Rolls-Royce made Merlins. Packard and Ford made Merlins. If it were mine, I would prefer a Packard or Rolls Royce Merlin, in no particular order, to a Ford Merlin, but all were good-running engines.


Quite right. 

Packard used British screw threads and even Whitworth threads/fasteners where the originals called for them to insure the best possible interchangeability. 
There were things changed but the changes were sometimes due to bought in parts (sub-contractors like the carbs) and had always been discussed before hand.

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## PAT303 (Sep 15, 2022)

Reluctant Poster said:


> Not quite Packard was moving into Buick territory in the late 30s. See my previous post.
> Post in thread 'An interesting read about the Packard built Merlin engine.'


What's interesting is the use of coolant tubes and seals between block segments on the Merlin, CAT 35 series engines use the same technique today and it's the most common engine in CAT mine trucks.


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## Reluctant Poster (Sep 17, 2022)

This video has an old news reel showing how Ford maintained tolerances for their new V8 in the 30’s. Start at the 14.30 mark. It is interesting to see that they weigh each piston and then use a special cutter to shave the inside of the piston to bring it into spec. They also weigh each con rod and piston together and them assemble then in matched sets. They also dynamically balance the crankshafts by shaving the counterweights and balance the flywheels by drilling holes.

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## yulzari (Sep 17, 2022)

Reluctant Poster said:


> This video has an old news reel showing how Ford maintained tolerances for their new V8 in the 30’s. Start at the 14.30 mark. It is interesting to see that they weigh each piston and then use a special cutter to shave the inside of the piston to bring it into spec. They also weigh each con rod and piston together and them assemble then in matched sets. They also dynamically balance the crankshafts by shaving the counterweights and balance the flywheels by drilling holes.



Is that not just production line hand fitting?

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## GregP (Sep 17, 2022)

No, it is not production hand-fitting. Hand fitting is fitting a part to another part. Production tolerances are ensuring a single part is within tolerance, and therefore interchangeable with other parts. Big difference.

Fitting each of many pistons to within 0.010" is much different than fitting a single oversize piston to an existing cylinder with a known eccentricity and known dimensions.

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## PBPICS (Sep 22, 2022)

CobberKane said:


> Okay, here's one for the technophiles (definitely not including me). The Allison engine in it's various guises has always seemed to play second fiddle to it's famous contemporary in the land of hope and glory, the Merlin. Was there any intrinsic design feature that precluded Allison engines from powering single engine fighters over Germany at 25000 feet, of was it all just a case of the American engine being hobbled by the thinking of the time - that high altitude fighters weren't required?
> To get full marks, please include an objective comparison of the beers of both countries.


As a former home brewer of craft beer, the devil is in the details. Excellent ingredients, meticulous technique, attention to details = excellent beer. Corn, rice as fillers don’t belong in great products. 
This actually relates to aviation in a direct way. I wouldn’t want to fly in an aircraft or with a flight crew that didn’t have those qualities as a baseline. Professionally speaking…in my former life as a tv news cameraman in New York…I’d take any opportunity to fly in any type of machine. It was mostly helicopters. Until there were several chopper crashes in NY and around the same time the news came out that the helicopter company that we used had the worst maintenance record in the region if not the country. I stopped volunteering to fly in their choppers while they were still being used. I will always love flying.


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## FLYBOYJ (Sep 22, 2022)

PBPICS said:


> As a former home brewer of craft beer, the devil is in the details. Excellent ingredients, meticulous technique, attention to details = excellent beer. Corn, rice as fillers don’t belong in great products.
> This actually relates to aviation in a direct way. I wouldn’t want to fly in an aircraft or with a flight crew that didn’t have those qualities as a baseline. Professionally speaking…in my former life as a tv news cameraman in New York…I’d take any opportunity to fly in any type of machine. It was mostly helicopters. Until there were several chopper crashes in NY and around the same time the news came out that the helicopter company that we used had the worst maintenance record in the region if not the country. I stopped volunteering to fly in their choppers while they were still being used. I will always love flying.


Just so you know the poster you're answering was banned over 8 years ago.


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