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So why were the Allison-powered Mustangs relegated to Army Cooperation tasks? Answer - because the Allison lacked altitude performance which was vital for 1940 because it didn't have the 2-stage supercharger as discussed previously in the thread.
Fair enough. Incidentally, is there definitive evidence of Allison serviceability being better than the Merlin in the Western Desert or is it simply that the P-40 was more associated with that campaign due to the publicity given to 112 Sqn's sharkmouthed aircraft?
Mustangs weren't available in the BoB, they came after...which is precisely my point. The Allison engine fitted to the Mustang MkIs lacked the altitude performance to enable the aircraft to be used in the fighter role so they were consigned to army co-op instead. If the early Mustangs couldn't hack the altitudes at which Fighter Command expected to operate, how would fitting an earlier version of the same engine to a Hurricane or a Spitfire in 1940 have improved things for the RAF in the BoB?
While Merlins were used in some coastal craft the majority of fast craft were powered by either Hall-Scotts (many of the Fairmile Launches) or Packard Marine engines which were NOT Merlins but a 2500cu in engine derived from a late 1920s aircraft engines.
The importance of the Battle of Britain is hard to overstate. The main reason for that importance is not because it saved Britain or influenced Barbarosa. The influence on an isolationist America containing a significant population of ethnic Germans, Irish, etc., who previously had no affinity for Britain was probably the most important aspect of the BoB. Allisons probably would have gotten the job done, but Readie is right. No one in Britain in their right mind would have installed anything but the well understood Merlin in a Hurricane or Spitfire at that time.
The first V-1710s with two stage compressors had an aftercooler, which loked very similar to teh one atop the Merlin 60 series. However, using that meant redesigning the engine supercharger intake and carburettor, or moving the carb to the auxiliary stage. By not having the aftercooler Allison was able to use a common engine stage supercharger and carb for all their variants - single stage, two stage, and turbocharged.
The loss of the aftercooler meant that ADI was required.
btw two stage Merlins had intercooling and aftercooling. The aftercooler is obvious in pictures, while intercooling was achieved by cooling passages around the supercharger casing. Maybe not super effective, but still there.
Shortround, This is interesting. I lifted the thread from British W11 wood boats.
Cheers
John
Which is just the point I have been making.
1. By not producing a 2 speed (that is single speed impeller speed not a two stage) supercharger, Allison limited the performance of the V-1710 in everything that did not use a turbo, P-39, P-40, P-51. Take a look at the performance graphs in America's Hundred Thousand. With two speeds you had a step in the performance where the first speed topped out and the 2nd, higher one kicked in. With nothing more than a 2 speed supercharger the Mustang Mk.1 would have topped 400 mph and been good for more than medium and low altitude. The P-40 and P-39 would have been better as well. They would not have been as good as with a 2 stage Merlin but better than they were.
Interesting but in rather direct conflict with the information in "British and Dominion Warships of WW II" by H.T. Lenton J.J. Colledge and in "Selected Papers on British Warship Design in World War II" Naval Institute Press, Chapter 5 Coastal Force Design by W J Holt.
For some pictures of the Packard try here: Packard V12 Marine Engine
It appears that very few R.N. craft had Merlins during WW II. RAF crash tenders may be different. British were importing and using Issota Fraschini engines in boats built before Italy joined the war in 1940. Fairmile As, Bs and Cs used Hall Scotts, the D boats used the big Packards.
...sent the impeller tips past supersonic and not gotten any better altitude performance.
Fair enough. Incidentally, is there definitive evidence of Allison serviceability being better than the Merlin in the Western Desert or is it simply that the P-40 was more associated with that campaign due to the publicity given to 112 Sqn's sharkmouthed aircraft?
True, every supercharger has its design limitation.I have a supercharger on my car and I can only increase its speed (17% decrease in pulley size) by a certain percentage before it overheats and the power curve falls.
Superchargers offer a great deal of boost,but they also take power to turn whereas a turbo is 'free' power with the exhaust gases.
Cheers
John
I think the Lancaster (and the follow-on development, the Lincoln) was handicapped by being Merlin powered.
Four turbo charged Allisons (basically the whole engine package from a P-38J/L) would have been more effective. More allitude capability compared to the Merlin 20 series in the Lancaster (equal to the Merlin 85 engines in the Lincoln) to help get above the flak and fighters. The stronger Allison power section could handle more power longer than the Merlin (good for the long climb to allitude) with less maintenance. Most importantly, the turbocharged Allison burned less fuel than a Merlin for the same horsepower, so more bombs for the same takeoff weight.
Griffon power in the Shackleton (another Lancaster follow-on) was also less than ideal. Allison had a turbocompound V-1710 running in their test cell. A single stage single speed version of a gas sipping Allison turbocompound would have been a better match to the Shackleton than the Griffon. (Note, this assumes that Napier misfires with their diesel work. They already had data and blueprints for the Jumo 205 diesel, a Deltic version of a Jumo 205 would have been could have been winner for long range patrol aircraft. Even the 'simplified' second version of the Nomad was wayyyyy too complicated. As with the Sabre, Napier reached too far).
I'm going to stand back after I send this post, just in case a vein in Readie's forehead bursts...
Piper106
The Lancaster from the BoB squadron will be arriving over your house sometime tonight to give you Readies response.
Actually, the Lancaster would have probably been a much better and more survivable bomber with four R2800s powering it.