Shortround6
Lieutenant General
Thank you
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Thank youI have the R-985 numbers from the 1975 overhaul manual, but not from WWII.
In 1975, R-985 TBO for helicopter engines was 500-800, agricultural aircraft engines was 600-1000 hrs, and 'long range' aircraft where cruise settings were the norm was 1000-1600 hrs.
Unfortunately, HP doesn't move airplanes, thrust does. So what is the thrust put out by that Cheetah @ 10k ft, or 20k or 30k vs the Jumo. Then factor in the thrust to weight ratio for both powerplants. For extra fun factor in the fuel weight as well but remember the cost of leaded high octane avgas vs jet fuel.To be fair the Cheetah X was only rated for 375 BHP at TO and a max of 355 BHP at 7,500 ft rated altitude.
On the other hand, based only on power output and TBO, the Cheetah X (355 BHP & 1200 hrs TBO) is 5.68x more efficient than the Jumo 004 (3000 BHP & 25 hrs TBO).
If you consider all factors that favour one engine to be paramount then that engine is favourite to be judged as the best. The war started in Europe in September 1939, being there in 1939 must be an important consideration, in my opinion.Unfortunately, HP doesn't move airplanes, thrust does. So what is the thrust put out by that Cheetah @ 10k ft, or 20k or 30k vs the Jumo. Then factor in the thrust to weight ratio for both powerplants. For extra fun factor in the fuel weight as well but remember the cost of leaded high octane avgas vs jet fuel.
If all you consider is the outright cost of the engine, then the 2-strokes powering drones were the best engines of the war.
But the question is what was the most efficiently built aircraft engine of the war.If you consider all factors that favour one engine to be paramount then that engine is favourite to be judged as the best. The war started in Europe in September 1939, being there in 1939 must be an important consideration, in my opinion.
trying to fit the needed 12 or so engines on a single seat fighter was a bit of problem.The Shvetsov M-11 has to be a contender. A 5 cylinder air cooled radial could be knocked up by Muscovite housewives before breakfast.
Great, but starting in 1939 for European engines and 1941 for engines from USA and Russia and add in a metric for minimum airframes in service and minimum engine life. An engine with a service life of 25 to 50 hours is experimental, you cannot run an air force with it.But the question is what was the most efficiently built aircraft engine of the war.
If all you care about is ease of production then it must be some low HP 2-stroke because those are the simplest and cheapest engines used on aircraft during the war. But thats probably not what the OP had in mind, is it?
So work out some metric for evaluating the relative performance of different engines used on manned aircraft. Then work out a metric of comparing the production costs, like manhours + raw materials. Now evaluate the relative performance against the relative costs. If you want to factor in availability then that is a different factor, like adding in fuel consumption or high-altitude perf or even accessory/armament issues.
only if you include the hand crank for the CheetahDoes all this include the Riedel starter engine ?
You are making a very big mistake in comparing HP of a jet engine to HP of a piston engine. Thrust is what makes aircraft go, not HP. You need to compare that instead.Hey blueskies,
The Jumo 004 put out ~1980 lbf static thrust at sea level. The 3000 BHP I listed for the Jumo 004 is the effective HP at ~560 mph at altitude. It is not exact as the efficiency of the Jumo 004 varied quite a bit at different speeds and pressure/density altitudes, but it is probably within 10%.
If we use the BHP divided by the weight of the engines, the value for the Cheetah X is ~.5 BHP/lb (355 BHP & 700 lbs) and that of the Jumo 004 is ~1.9 BHP/lb (3000 BHP & 1600 lbs). That makes the Jumo 004 about 3.8x as efficient as the Cheetah X in terms of HP/lb.
So if we divide the 5.68 value by 4 we get the Cheetah X coming out on top by a factor of 1.49.
If we throw in the man-hours labor per engine I think the Jummo 004 would come out ahead by a small margin, but if we use the total manufacturing costs including tooling and engine materials I suspect the Cheetah X would increase its lead. Unfortunately I do not have any info on the actual man-hours needed or the wholesale cost for the Cheetah X.
Yes, but by the time jet engines were entering service in non-experimental fashion, what was the average lifetime of a Luftwaffe piston fighter before it was shot down or strafed/bombed on the ground? Wouldn't surprise me if it was less than 25 hours?Early German jet engines had a life of 25 hrs, so to compare to an engine that goes 300 hrs before it needs a major service you need 12 engines or 3,600 man hours.
ISTR that the TBO of the Napier Sabre was 25 hours well into 1943.An engine with a service life of 25 to 50 hours is experimental, you cannot run an air force with it.