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

[Aozora]

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):

 

[GregP]

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.

 

[Shortround6]

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.

 

[GregP]

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.

 

[Jugman]

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.

 

[GregP]

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.

 

[tomo pauk]

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.

 

[Balljoint]

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.

 

[nincomp]

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

 

[GregP]

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.

 

[zjtins]

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.

 

[tomo pauk]

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.

 

[wuzak]

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.

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.

 

[tomo pauk]

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?

 

[zjtins]

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.

 

[wuzak]

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.

 

[CobberKane]

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?

 

[Shortround6]

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

 

[zjtins]

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.

 

[XBe02Drvr]

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