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R-2800A, in 1-stage variation, was supposed to do 1500 HP at 14000 ft on military power. That is 40+% better than any in-service V-1710 before late 1942 - quite an advantage.
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The big radials did not offer the performance at altitude over the Allison that the take-off power figures suggest. Not without using cowlings and exhaust set ups that were not used historically until later in the war.
Using a late 30s (P-36) state of the art cowling the P-36 had either a 22% increase in drag over the P-40 or a 22% loss due to drag and poorer exhaust thrust.
Take 22% away from the R-2600 A series at 12,000ft and you wind up with just a bit less power than the Allison -39 engine.
The R-2800 A series does a bit better (and is smaller in diameter) but is over 350lbs heavier than the Wright engine. Which is almost 600lbs heavier than than Allison (of course the Allison needs nearly 300lbs worth of radiator and coolant).
I wouldn't do this to replace the b-29, although it could accept some missions the B-29 flew. Rather I would replace the B-17/24 as fast as I could (26000 eighth AF men died (this number also include fighter losses but by far the most were bomber losses)). I think thousands of lives would have been saved had we had a faster modern bomber instead of lumbering old tech bombers.This would require working out the turbo bugs for the R-2600. And it wouldn't carry the A-bomb when that was ready (at least not a useful distance) so you still need the B-29. Possibly too much even for American industry.
I've also pondered the missing generation of heavy bombers using R-2600 or -2800. But unless you get B-29 level performance by using 6 engines this might be one gap that doesn't need filling.
The big radials did not offer the performance at altitude over the Allison that the take-off power figures suggest. Not without using cowlings and exhaust set ups that were not used historically until later in the war.
Using a late 30s (P-36) state of the art cowling the P-36 had either a 22% increase in drag over the P-40 or a 22% loss due to drag and poorer exhaust thrust.
Take 22% away from the R-2600 A series at 12,000ft and you wind up with just a bit less power than the Allison -39 engine.
The R-2800 A series does a bit better (and is smaller in diameter) but is over 350lbs heavier than the Wright engine. Which is almost 600lbs heavier than than Allison (of course the Allison needs nearly 300lbs worth of radiator and coolant).
you are comparing a loss of speed with the change in drag. They are not quite the same thing.22% seems high. According to Ray Wagner, a P-36C, with 1050 hp at 10,000 ft, had a top speed of 311 mph at 10,000 ft. The XP-40, with 1000 hp at 10,000 ft, had a top speed of 342 mph at 12, 200 ft. or a loss of about 10% loss. This is probably as close as we can get to a one to one comparison.
I wouldn't do this to replace the b-29, although it could accept some missions the B-29 flew. Rather I would replace the B-17/24 as fast as I could (26000 eighth AF men died (this number also include fighter losses but by far the most were bomber losses)). I think thousands of lives would have been saved had we had a faster modern bomber instead of lumbering old tech bombers.
As far as turbo design is concerned, I think the consistent operational parameters of bombers simplify design.
Clean up the landing gear on the P36 and P40. The Zero was very clean and very fast on not much HP, so lets help ourselves by cleaning up the airframe so we get the best out of the available engines
You may very well be correct, but if a bomb/drop tank mount cost 10 mph (several tests on wwiiaircraft performance show about 10 mph for a drop tank mount) how much speed did that P36/P40 landing gear cost? 20 mph? More?"Cleaning up the landing gear" on the P-40 would likely require a new wing.
That's the trouble with aft folding landing gear; stuffing a robust wheel/strut assembly into a wing at near its thinnest point. An improvement of sorts over fixed gear, but a much greater penalty on a plane groping towards 350 mph than on its 250+ class predecessor. If you look at the innards of the wing center section area, there just isn't room for inward folding gear, and outward folding like the ME and Spit is a non starter on a plane that's likely to operate off rough fields with pilots who are new to the low wing, all metal, folding feet monoplane business. Remember, Curtiss had a thriving export business before the Hawk 75 line came along.how much speed did that P36/P40 landing gear cost? 20 mph? More?
Great feedback. To clarify, when you said "Can you imagine enclosing that gear well with fairings and tightly fitting streamlined doors, then trying to operate off a bumpy, muddy field in China or New Guinea?" did you mean enclosing the wheels on the current setup? My goal would be to eliminate the big fairings on the front of the wing where the landing gear attatches, which I agree would need a new wing. They need to be moved out farther and retract inward.That's the trouble with aft folding landing gear; stuffing a robust wheel/strut assembly into a wing at near its thinnest point. An improvement of sorts over fixed gear, but a much greater penalty on a plane groping towards 350 mph than on its 250+ class predecessor. If you look at the innards of the wing center section area, there just isn't room for inward folding gear, and outward folding like the ME and Spit is a non starter on a plane that's likely to operate off rough fields with pilots who are new to the low wing, all metal, folding feet monoplane business. Remember, Curtiss had a thriving export business before the Hawk 75 line came along.
SwampYank is right, a wing redesign would be in order. Can you imagine enclosing that gear well with fairings and tightly fitting streamlined doors, then trying to operate off a bumpy, muddy field in China or New Guinea?
Cheers,
Wes
Roger that. Concur. The trouble is that by the time the need became evident, the design was cast in stone, the tooling in place, and production was pell-mell. We all know of the multiple attempts at an enhanced P40 which came to nought because the changes were too great and the improvement too small.My goal would be to eliminate the big fairings on the front of the wing where the landing gear attatches, which I agree would need a new wing. They need to be moved out farther and retract inward.
And lets remember that the XFU-1 first flew in 1940 making a single stage, two speed R-2800 powered fighter rather 2nd rate to Navy
XF4U-1? The Flying Flapjack didn't really go anywhere . . . Not a Navy thread but ironically single stage 2 speed is what they ended up wanting with the Bearcat and Tigercat.
Anyway getting more 2 stage planes to the Marines/Army in 1942 is what we need, whether P-43, F4F, or accelerated F4U. I wonder also if Mustang airframes could have been shipped to the UK and mated with British Merlin 61 production before Packard comes on line?
Kind of related dumb supercharger question - when engines were cleared for higher boost pressures, was that exploited simply through using more throttle at low altitude? I.e. you didn't need to change supercharger gear ratios or anything like that (which seems like a major mod to do in the field)?
I believe that the British converted a P-51 to have a Merlin as a proof-of-concept, so they could probably do a conversion. Are you asking if it would have made sense for North American to ship the RAF engine-less P-51s for completion in the UK? I'm not sure the UK had the industrial capacity needed for that without adversely affecting another program.
The British had about 4 squadrons of Spitfire IXs in Aug of 1942. They had about 10 squadrons in the late fall or turn of the year. Without crippling Spitfire IX production you aren't going to get very many Merlin powered Mustangs much earlier than historically. There was a plan put forward to send engineless Mustangs to England but it was rejected.