When You Want a B-29, but V-12 is Life

"Jcarr" (jcarr) 08/22/2017 at 13:06 • Filed to: Planelopnik

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The XB-39. A B-29 fitted with 4 Allison V-3420 W-24s (twin V-12s sharing a crank).

Demon-Xanth knows how to operate a street. > Jcarr 08/22/2017 at 13:21

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Not a common crank, but a common output shaft:

Jcarr > Demon-Xanth knows how to operate a street. 08/22/2017 at 13:28

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Good catch. I read “common crankcase” on the wiki and saw “common crank”.

Demon-Xanth knows how to operate a street. > Jcarr 08/22/2017 at 13:31

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So it’s more like “Yo dawg, I heard you like V12s, so I put a V12 on your V12.”

Bman76 (hates WS6 hoods, is on his phone and has 4 burners now) > Jcarr 08/22/2017 at 13:42

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The XB-38 is still the prettiest bomber of the era, maybe all time (B-17 with V-12s)

user314 > Jcarr 08/22/2017 at 13:47

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And none of the planes that the V-3420 would have powered ever saw mass production. A shame, given the deficiencies of the early R3350s:

The engines remained temperamental, and showed an alarming tendency for the rear cylinders to overheat, partially due to minimal clearance between the cylinder baffles and the cowl. A number of changes were introduced into the Superfortress’ production line in order to provide more cooling at low speeds, with the aircraft rushed into operational use in the Pacific in 1944. This proved unwise, as the early B-29 tactics of maximum weights, when combined with the high temperatures of the tropical airfields where B-29s were based, produced overheating problems that were not completely solved, and the engines having an additional tendency to swallow their own valves. Because of a high magnesium content in the potentially combustible crankcase alloy, the resulting engine fires — sometimes burning with a core temperature approaching 5,600 °F (3,100 °C) [1] from the Duplex Cyclone’s magnesium engine crankcase alloys — were often so intense the main spar could burn through in seconds, resulting in catastrophic wing failure.

Jcarr > user314 08/22/2017 at 13:54

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That’s terrifying.

CaptDale - is secretly British > Jcarr 08/22/2017 at 16:24

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I want to shove one of those in a prewar racecar replica

Jcarr > CaptDale - is secretly British 08/22/2017 at 16:35

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You mean you want to shove a prewar racecar replica on to one of these.

CaptDale - is secretly British > Jcarr 08/22/2017 at 16:50

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YES!