R975 Radial engines

[Hanno Spoelstra]

Hello Bob,

Over a year ago I came across pictures of a Continental R-975-46A radial engine for sale for not too silly money. I too wondered about the interchangeability of parts, or even a complete engine swap into a M4 Medium tank or related AFV.

Thanks for offering some insight into the detail differences.

Hanno

PS: Here's what I found about about it:

Continental R-975-46A radial: from aero, to tank, to aero engine

Aircraft variant of the Continental R-975. This is the -46A version as used post-WW2 in the Piasecki PV-18 (Navy HUP-3 Retriever, Army H-25A Army Mule) helicopter. It was offered for sale on the Antique Aircraft Parts Exchange FB group, and shared here as it may be of interest to Sherman tank restorers. While originally a Wright design, during WW2 Continental built more R-975's under licence for tanks than Wright did for aircraft (> 53,000 vs. >7,000). After the war, Wright showed no interest in continuing to manufacture the R-975. Continental then introduced its own R-975 version for aircraft, the R9-A. It was basically similar to other R-975 engines, and its compression ratio and supercharger gear ratio were unchanged from the R-975E-3, other improvements in the R9-A allowed it to achieve 525 hp (391 kW) for takeoff, surpassing any Wright version. A military version, the R-975-46, could reach 550 hp (410 kW), and was used in Piasecki's HUP Retriever and H-25 Army Mule helicopters. Continental's production of R-975 engines continued into the 1950s.

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Power to the HUP-1, HUP-2 and HUP-3 helicopters is supplied by Continental R-975-42, R-975-46 or R-975-46A air-cooled, nine cylinder radial engines. These were based on the Wright-designed tank engine.

The engine is located within the fuselage aft of the fuel cell and firewall. It simultaneously drives two three-bladed rotors through drive shafts and reduction transmissions. The rotor blades of the HUP-2 are of either wood or metal (later versions) construction.
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Continental R-975-42 as used in the Piasecki PV-18 (Navy HUP-2, later UH-25 Retriever)
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