No US-built Merlin: plausible developments?

[davebender]

Any aircraft can stand off and launch rockets including passenger aircraft such as the Ju-52 and Boeing 747. But they are hardly ideal for that purpose.

 

[Shortround6]

Any aircraft can stand off and launch rockets including passenger aircraft such as the Ju-52 and Boeing 747. But they are hardly ideal for that purpose.

Yep. any aircraft can launch rockets. getting the rockets anywhere near the target aircraft is a whole other story.

Granted it is wiki but:

Werfer-Granate 21 - Wikipedia, the free encyclopedia

Trying to hit (get rocket to explode within several hundred feet) planes flying several thousand meters higher and flying faster than the Ju 52 would have been like hitting the lottery with your first ticket. It also would have required changing the time fuse to allow for a much much longer flight time. You might want to do a little elementary geometry and try to figure out even the most optimistic flight times to intercept a bomber flying 5000ft higher than the Ju 52 and cruising at 180mph true airspeed.

 

[tyrodtom]

The R4M had a little more range WG-21, it was 1500 meters. Which is about the same as the shortfall of the Ju-52's service ceiling with the very lowest flying formations of daylight bombers. But most of the formations were a great deal higher than 22,000.

Plus I doubt even the R4M had a 1500 meter range when fired straight up, because that is the only way any rocket in the Luftwaffe's inventory had any chance of hitting allied daylight bombers when fired from a Ju-52.

 

[Shortround6]

Well, the WG-21, in a ground roll, could range to just under 8000 meters when fired at a 45 degree angle. Air at 15,000-20,000ft is about 30-40% thinner so it should range further. If our intrepid JU 52 pilot can get his aircraft to 15,000ft and then pull up 25-30 degrees (With the tubes mounted at 15-20 degrees.) the rockets might just make it to 20,000-22,000ft 12-15 seconds after launch (time fuse modified). Of course in 12 seconds even a slow B-17 has moved over 3000ft so "aiming" is a bit of a problem.

Of course getting the Ju 52 to 15,000ft with the extra drag of the external tubes is a bit of a problem (mount the tubes inside the fuselage?) as is the 30 degree pull up at max height (almost a guaranteed stall) (solved by internal tubes).

I can believe a number of aircraft besides the ones listed in Wiki might have carried the big rockets. the JU 52 wasn't one of them.

 

[GregP]

Shortround,

Parsfail said decision about what to produce in 1942 had to be made. They produced 1 engine per month in 1938, 8 engines per month in 1939 … per contract. In 1940, it was up to 300 per month and in 1941 it was 1,100 per month. By 1942, it was 1,400 per month.

Allison went from 94,000 square feet on manufacturing space in 1938 to 1,221,660 square feet in 1940. Allison delivered only 1,143 engines in 1940, when we were not at war, and delivered 6,447 in 1941. That qualifies as mass production in my book. In 1942, they delivered 14,905 engines. Like I said, mass production.

Numbers from Dan Whitney's Vees for Victory.

 

[tyrodtom]

If you mounted the tubes in the fuselage, what would happen to the fuselage when the rockets fired ?
While the Iron Annie might have been tough, I think that sounds like a one way mission.

 

[Shortround6]

Shortround,

Parsfail said decision about what to produce in 1942 had to be made. They produced 1 engine per month in 1938, 8 engines per month in 1939 … per contract. In 1940, it was up to 300 per month and in 1941 it was 1,100 per month. By 1942, it was 1,400 per month.


Numbers from Dan Whitney's Vees for Victory.

Parsfail was in error, the decision was made in 1940. While Allison had large orders on the books and was doing a fine job of gearing up FOR mass production in the spring/early summer they had not achieved it yet. In 1942 the Allison was in mass production, In 1940 it depends on the month you look at. Another source gives 1149 engines in 1940, a difference of 6 engines isn't worth arguing about. However of those 1143-9 engines 943 of them were delivered in the last 4 months of 1940. It takes time to expand plants and tool up and get rolling, at the actual time in 1940 when the decision to build the Merlin in the US was being made the Allison, while well on it's way was not actually in mass production.

 

[Shortround6]

If you mounted the tubes in the fuselage, what would happen to the fuselage when the rockets fired ?
While the Iron Annie might have been tough, I think that sounds like a one way mission.

Might be a one way mission if the Ju 52 stalls and goes inverted at 15,000f too.

I hope you realize I am joking about the Ju 52

Very good 1930s transport, lousy bomber interceptor no matter what you stick on/in it.

 

[parsifal]

That's a bit of exaggeration there dave. If the Luftwaffe was getting short of fuel before the USAAF got there, it would be because they just didn't produce enough, because no one had targeted petrol production to any serious extent up to that time.

In 1939, that would be the USAAC, less than 60 B-17s by the middle of 39, the P-40 first flew in late 38. So a American effort at bombing in 1939 would be B-18s escorted by P-35s and P-36s. That would be a sad exhibition.

I agree that dave is doing what he does best here, but still, its true that the Germans were in crisis in terms of fuel supplies from quite early in the war.

The Germans suffered their first fuel crisis in 1942. There are two ways of looking at this....either, as you say the germans didnt produce enough fuel, or, as an alternative way of looking at it, their consumption exceeded what they had planned for. Im not just being cute with the words here....Fuel consumption in 1941 far exceeded expectations, particularly in the East, where logistics created chronic shortages for the germans. In fact the logistics constraints always meant the germans were short on supply in all their distant TOS, like North Africa and the Eastern Front.

Production fell short of demand, because production costs for manufactured fuel were very high....about 10 times the cost per gallon as naturally occurring fuel. The British blockade cut the germans from their traditional overseas supplies, and British bombing, whilst somewhat inneffective, still had an effect on distribution and did include fuel supplies as one of its target priorities (albeit not a primary objective). The germans had hoped to augment their meagre supplies by captured sources, but all wells that were captured were effectively destroyed for the duration. The picture is completed by germany's attrocious attitudes towards its allies. Whereas the allied efforts tried to work to each alliance members' strengths, and compensate for each others weaknesses, the germans from the very beginning treated nations like Rumania and the occupied territories as colonial outposts to be exploited and cheated as much as was humanly possible. The Rumanians returned that treatement in kind. There was never a high level of co-operation in the Axis camp as existed in the Allied camp (though tensions did exist, of course). One result was that the Germans sold armaments to Rumania for inflated prices, and the Rumanians were in no hurry to increase production to meet demand. why would they when Germany was not prepred to pay what that oil was worth to them?

Explaining why Germany came up short in the supply of oil is more complex than it looks. and trying to attribute the final oil crisis as a result of the 8th AF's precision bombing campaign of 1944-5 is just a partial answer to that equation. it does not explain all the issues

 

[gjs238]

Could R-2800 2-stage supercharging development have been improved?
While this would not have helped the P-40 or P-51, it could have been interesting to see F4U's in the ETO up high providing escort.
Not sure how the Brits could have utilized a 2-stage supercharged R-2800 w/o aircraft design changes.

 

[tomo pauk]

Question: If Packard aren't building Merlins in 1942 is it because Packard or the US Government rejected the request from Rolls-Royce/British Governemnet?

If this is rejected, what of the Tizard mission? Will he take all his goodies (cavity magnitron, jet engine planes, other bits of British technology) back home with him?

Hi,
I'm not questioning/jeopardizing the Tizard mission, just trying to create a discussion about the non-production of the Merlin in the USA and the repercussions of that. In this thread, Packard builds either R-2800 or V-1710 instead.

Could R-2800 2-stage supercharging development have been improved?

Hi,
What kind of improvement you have in mind? The 2-stage R-2800 was one hell of an engine.

While this would not have helped the P-40 or P-51, it could have been interesting to see F4U's in the ETO up high providing escort.

Would it be so unreal to up-engine the P-51 with R-2800?

Not sure how the Brits could have utilized a 2-stage supercharged R-2800 w/o aircraft design changes.

Perhaps the Brits would be better off with single stage R-2800, than the Hercules engines they were using in Beaufighters and heavies? The R-2800 looks like a great way to power post-Hurricane Hawker fighters; the installation can be akin of that of Hellcat.

 

[Shortround6]

Could R-2800 2-stage supercharging development have been improved?

I would agree with Tom on this, improved how?

At higher altitudes it had several hundred more HP than a single stage R-2800 and would never have the power of a turbo R-2800. The auxiliary stage took about 350hp to run and if we assume a poor efficiency of 70% that means 245hp is compressing the air and and 105hp is heating it. If you could improve the efficiency to 80% you would only need about 306hp freeing about 44hp on a 1650hp engine but with only 60hp heating the air instead of 105hp the intake charge would be a bit cooler/denser meaning a bit more power. 80% efficiency is about tops for a WW II centrifugal compressor though. Or swap a bit more pressure for a lower efficiency? A few more lbs manifold pressure at 75% E.
That was the attraction of the turbo, using the exhaust gasses to power a turbine to reclaim 300-400hp to drive the supercharger.

While this would not have helped the P-40 or P-51, it could have been interesting to see F4U's in the ETO up high providing escort.

Interesting yes, but one has to consider that historically the F4U-1 was down a minimum of 350hp compared to a P-47 (at 22,500?) and in later versions the P-47 could have 2280hp at 25,000ft while climbing using water injection while an F4U-1 with water injection could only manage 1600hp at 25,000ft in level flight(P-47 could hold 2200hp in level flight to 30,000ft) at which altitude the F4U-1 might have only 1200hp left. an extra 1000hp (83% more) goes a long, long way in making up for the P-47s extra weight and bulk over the F4U-1.

Not sure how the Brits could have utilized a 2-stage supercharged R-2800 w/o aircraft design changes.

I am not even sure how they could use a single stage R-2800 w/o aircraft design changes. It is far from a plug in replacement for the Hercules. An Early Hercules weighs about 1850lbs dry for 1590hp take off and a max continuous of 1300hp at 14,800ft. A Wright R-2600 "B" series weighs about 1980lbs for 1700hp take off and 1350 max con at 15,000ft. A single stage 2 speed R-2800 went 2300lbs for 2000hp take off and 1450hp max con at 13,000ft. the extra 25% power at take off is going to need a bigger propeller than the Hercules had. The R-2800 is probably going to go 550-650lb dry (no oil) more installed per engine than Hercules.
Perhaps not a problem on a some planes but sticking an extra 1200-1300lbs in the cowlings of a Beaufighter could prove very interesting to an observer
Test pilot might describe it differently.

 

[Shortround6]

The R-2800 looks like a great way to power post-Hurricane Hawker fighters; the installation can be akin of that of Hellcat.

???????

Post Hurricane Hawkers either had the Sabre (which could use help) or were planned for the Centaurus. The R-2800 is about 85% the size of a Centaurus so most things being equal (single stage superchargers, same fuel, etc) the R-2800 is going to be down about 15% in power from the start. Not sure the British are going to want to invest time and money in inferior versions of the aircraft.

compared the Sabre the R-2800 is down in power (but not as much) while having more drag. Not a good combination for performance even if much more reliable.

Without the two stage supercharger the R-2800 has the same problem the R-2600 does as a fighter engine, lousy performance at altitude. 1600hp at 13,500 ft in high gear Military power for the version installed in the A-26 bomber and later B-26 bomber, early versions were worse. Like 1500hp at 14,000ft in high gear. Compared to what the Merlin could put out even it's MK XX form the R-2800 single stage is a much better bomber engine than fighter engine.

 

[parsifal]

Post Hurricane Hawkers either had the Sabre (which could use help) or were planned for the Centaurus. The R-2800 is about 85% the size of a Centaurus so most things being equal (single stage superchargers, same fuel, etc) the R-2800 is going to be down about 15% in power from the start. Not sure the British are going to want to invest time and money in inferior versions of the aircraft.

Granted if you assume a single stage supercharger and different fuels, you might be able to explain difference in the power outputs of the two engines. Also concede that at the time of service delivery, the early marks of the Centaurus, as fitted to the Typhoon, were rated at 2250HP. The centauraus during its service career was significantly improved over roughly a two year period. The Bristol Centaurus has 18 cylinders in two rows, and is a sleeve-valved radial air-cooled engine. The first version produced 2,000 bhp, and the most powerful variant produced 3,200 bhp. It was the ultimate Bristol piston engine originally designed for use in Heavy bombers. Over 8,000 were produced. It is difficult to make blanket comparisons between the two engines since both were considerably improved over time. I am not sure why you would want to make assumptions about lower powered superchargers, since the improvements to the supercharger fitted to the centaurus was a major focus of the development program.

The Centaurus was a sleeve valve radial aircraft engine, an 18-cylinder, two-row design that initially delivered 2250hp but by 1945 delivered over 3,000 hp under combat conditions using standard wartime high octane rated fuels (I dont know the exact octane rating). This was the rated power output of the engines fitted to the Sea Fury FB11, introduced post war. These aircraft attracted a fine reputation for engine reliability and high engine power outputs. It was one of the largest piston aircraft engines to enter production, and was introduced into service use towards the end of World War II.

When the R-2800 was introduced in 1939 it was capable of producing 2,000 hp (1,500 kW). No other air-cooled engine came close to this figure at that time. The type was also noteworthy for its great reliability.

In 1941 the power output of production models increased to 2,100 hp (1,600 kW), and to 2,400 hp (1,800 kW) late in the war. Even more was coaxed from experimental models, with fan-cooled subtypes producing 2,800 hp (2,100 kW). However experimental versions of the Centaurus also managed to produce up to 3400hp.

 

[gjs238]

I was thinking if it was possible to improve the development process, not necessarily the end product.
If the 2-stage supercharged R-2800 could be brought into service earlier, perhaps it could mitigate the lack of V-1650's.

However, if turbocharging is really so much better, then perhaps using turbocharged V-1710's and/or other 1-stage supercharged engines for high altitude ops in lieu of the V-1650's is a path to explore.

 

[Shortround6]

I was going from the point of view of no US production of Merlins in 1940, and trying to substitute R-2800s in the 1940-42 time frame, Hawker was working on the Typhoon in 1937 and flying prototypes of the Tornado and Typhoon before the talks with Americans started and may well have been working on the Centaurus version at the time, R-2800 was giving 1850 hp for take off and promising 2000? British engines were delivering 2000+ and promising even more. Spending time and effort to design installations for the R-2800 in 1940/41 makes little sense as the R-2800 was under powered (at the time) and of higher drag than the Vulture or Sabre.
R-2800s were used one Version of the Vickers Warwick bomber.
ALL of these engines, with the exception of the Vulture, made great strides in development and finished the war much more powerful than they started but the decisions as to which one to use in what aircraft in 1941-43 cannot be made on the basis of 1944-45 performance.

perhaps 2-stage supercharged R-2800s could have substituted in a way for V-1650s but Pratt only delivered 6 two stage R-2800 engines in all of 1941 and 117 in the first 6 months of 1942. They had delivered 98 two stage R-1830s in 1940 and another 507 in 1941. The early R-1830s gave a fair amount of trouble. How much can you speed up the development ( and the P&W two stage needed a lot of room in the airplane for the inter-coolers) vs when does the decision have to be made as to which engine to produce?

Parsifal, I believe the 2000hp version of the R-2800 shows up in 1941 (4 single stage engines built, 2 by East Hartford and 2 by Ford) This is the "B" series engine. the 2100hp "C" series doesn't show up until 1943 in single stage form and 1944 in two stage. Any R-2800s in 1940 and 1941 except for the above mentioned 10 engines and few experimentals are 1850hp "A" series. The even later "CA" series could make 2300hp for take off. All of these are dry (without water) and the addition of water injection and WEP settings ( not always the same thing, P&W rated the engines with water injection. P&W did not assign WEP settings in factory literature) confuses things somewhat. There were a few "D" series engines made for the XP-56 and other pushers? and the F8F Bearcat and F4U-5 used "E" series engines and don't really need to concern us.

 

[GregP]

Shortround,

You are correct in 1940 but, in 1940, we were not at war and the Allison was exactly what was needed. We didn't go to war until December 8th, 1941, and 1942 was just around the corner, and the Allison was in mass production exactly when needed. The first Packard-built Merlin didn't run until August 1941. We STILL WERE NOT AT WAR and the A llison was ramping up nicely.

They didn't ramp up until 1942, and the Allison was in production by then. What it needed was the 2-stage, 2-speed supercharger of the V-1650-3, using the Wright supercharger drive quill instead of the Farman unit of the V-1650-1 Merlin. This could have been achieved rapidly if Congress had simply appopinted an Allison manager authorized to make imp[rovements to the engine. Instead, they clung to the original design most of the way through the war and never delegated imnprovement to anyone. Stupid, really ... and preventable.

 

[wuzak]

Shortround,

You are correct in 1940 but, in 1940, we were not at war and the Allison was exactly what was needed. We didn't go to war until December 8th, 1941, and 1942 was just around the corner, and the Allison was in mass production exactly when needed. The first Packard-built Merlin didn't run until August 1941. We STILL WERE NOT AT WAR and ethA llison was ramping up nicely.

Packard production of the Merlin was primarily to give another supply source for the UK. The US government only agreed to it providing there was a proportion (1 in 3) to be supplied to the US.

 

[Shortround6]

That is pretty much it. The US was not approving production of British designs/weapons unless the US thought they would be able to use them too at a later date. The US had two medium sized radials and 2/3 large radials but only one liquid cooled engine any where close to production or in production so a second one (already proven) would not be hard to find uses for.


Edit. The US and Allison were aware of the limitations of the single speed supercharger on the Allison fairly early. The design of the XP-39E (XP-76)

With the V-1710-47 engine in 1941 shows they were not ignoring the situation. Perhaps not giving the full priority but with 4000 planes ordered at one point certainly not ignoring it. That all 4000 planes were canceled shows that initial hopes/projections were not being met for a number of reasons and faster results were expected elsewhere.

 

[tomo pauk]

???????

Post Hurricane Hawkers either had the Sabre (which could use help) or were planned for the Centaurus. The R-2800 is about 85% the size of a Centaurus so most things being equal (single stage superchargers, same fuel, etc) the R-2800 is going to be down about 15% in power from the start. Not sure the British are going to want to invest time and money in inferior versions of the aircraft.

compared the Sabre the R-2800 is down in power (but not as much) while having more drag. Not a good combination for performance even if much more reliable.

Without the two stage supercharger the R-2800 has the same problem the R-2600 does as a fighter engine, lousy performance at altitude. 1600hp at 13,500 ft in high gear Military power for the version installed in the A-26 bomber and later B-26 bomber, early versions were worse. Like 1500hp at 14,000ft in high gear. Compared to what the Merlin could put out even it's MK XX form the R-2800 single stage is a much better bomber engine than fighter engine.

Hold you horses...err, question marks. I've already said:

The R-2800 looks like a great way to power post-Hurricane Hawker fighters; the installation can be akin of that of Hellcat.

That means an, almost, power egg installation (not as much as distributed as in Corsair), and 2-stage R-2800.