- Jun 29, 2009
You need to get around the US Army prejudice against air cooled engines. One reason for the whole hyper engine program. Granted it came to nothing but air cooled engines were viewed as difficult to cool at high (turbo) altitudes. Air at 20,000ft for instance is about 73% as dense as sea level which means you need a lot more airflow over the cooling fins of the radial engine. Yes you need more airflow through the radiators of the liquid cooled engine/s. but you don't need to actual change the engines, just the radiators/ducts. They were also fooling around with the ethylene glycol coolant and different coolant temperatures (too high didn't work) and settled on the glycol/water mix and pressurized system right about 1940-41.Clipper was also a product of months of the work in the design bureau and in the workshops, it didn't just materialized a few weeks before the maiden flight From Wikipedia:
Boeing's bid was successful and on July 21, 1936, Pan American signed a contract for six.
That is a 13 months before the contract was awarded to the XP-38. The not-P-38 needs to be mooted around one 1500 HP engine from the start.
The Army was specifying turbo-charged airplanes, They ordered 50 of these in in 1934
and the last were delivered in Aug. 1936. It had....." it was the first fighter in service with the USAAC to have a fully retractable undercarriage, it was the first fighter with a constant speed propeller, and it was the first truly successful application of a supercharger to an operational military aircraft. " The last may be a bit debatable but the Airacuda's were supposed to have turbos, the YP-37s (ordered in Dec 1937, first delivered in June of 1939.)
The Army had the non-turbo P-36s and later the non turbo P-40s as back ups.
for some reason the R-2600 fell through the cracks. GE only made two sizes of turbo. The smaller one didn't flow enough air for the R-2600 and the bigger one, if available in the late 30s, was intended for engines that were powerful than the R-2600, like the R-3350 and R-2800 and some of the experimental engines.
Wright was improving cooling (among other things) but they kept increase the regular power out put.
Where was the 1750hp engine? what model number?GE was not Bell, promissing the moon and failing to deliver, time after time.
If the 1500 HP engine will not cool well at 20000 ft, we can have the 1600 HP engine installed and down-rate it to 1500 HP. Or by 1941 install the 1750 HP engine and either down-rate it to 1600 HP, or go (oh, heresy) with R-2800. Cooling fan was also trialed in 1941 by NACA.
Still a 390- and later 400-mph aircraft.
The 1700hp engine had design work start in Nov 1938, first test engine ran in Nov 1939 and the 5th production engine showed up in June 1941.
At what point do you decide that the 1700hp version was actually going to work and decide when to adopt it for your planned fighter?
a little back ground or side development/cautionary story.
In 1938 he Army was not happy with progress that Continental was making with ??-1430 engine and contacted Wright for a liquid cooled engine.
Wright responded with 4 different rough designs with notes on advantages and disadvantages. At this time the Army was still pushing for engines buried in the wings.
Wrights conclusion was that there was too much trouble with such installations. Like you can't use a mono spar wing construction. and spar spacing on multi spar wings was difficult.
In Jan 1939 an installation drawing (external size of the engine for airframe makers) was released for the Flat X 24 cylinder version.
By April of 1939 Wright had given up on the initial proposals 1500-1800hp Flat X and was pushing the 1800hp version of the 42 cylinder 6 row radial engine with liquid cooling (but adaptable for air cooling). In June of 1939 an new installation drawing for the 1800hp engine was released to the airframe makers for the small diameter 42 cylinder engine.
By this time the airframe makers were no longer interested in an 1800hp engine but were interested in a 2500hp engine. Bore was increase as was stroke and the engine would up as the R-2160 Tornado. A new installation drawing was released. And by Aug 1939 a supplement to original report was released with the R-2160 sales pitch, like modular engines of 14 and 28 cylinders (or as many as 56) and left and right prop rotation, coaxial-contrarotating propellers, and two speed propeller drives. Wight was also including superchargers of single speed plus turbo, two speed single stage, and two stage.
In June of 1939 a contract for a 14 cylinder test rig was obtained.
By the time the program ground to a halt in the spring of 1943 (no prototype aircraft would be using the engine, the prototypes had either been canceled outright or had been changed to other engines), it took until Spring of 1944 for Wright and the government to negotiate the cancelation/conclusion of the various contracts and disposition assets of the program
Wright had spent about $6,170,000 of it's own money.
At one time at least 4 aircraft were slated to use the engine, including the Lockheed P-58 and the Republic P-69.
At the time everything stopped they had 1,631 hours between six 42 cylinder engines, 1200 hours on two 14 cylinder engines and 130 hours on a 6 cylinder test rig.
The two V-12s have a smaller frontal area than the R-2600 although the radiators/oil coolers will pretty much cancel that out.A fighter with two V12s will also have two cooling systems to add drag, and the central pod/fuselage to add drag.
R-2800 was much earlier to have 2-stage supercharger, preceding such an R-2600 by 15-18 months? That's eternity in the lead up for the ww2. An extra of 100-250 HP is also worth mentioning.
You pretty much have to pick out the engine/s at certain point in time and go with it. You might be able to change V-12s, a lot harder to go from twin to single or back.