Fairchild KR-31, NX4676, sn X-205

120 hp 477-C Fairchild Caminez

This is a four cylinder Radial Cam Engine. There are two lobe in the cam crankshaft thus there are twice as many power strokes per revolution as compared to a normal engine. The 120 hp rating is at only 960 rpm. Thus the need for more blades on prop.

This engine was plagued with vibration problems. Damaging wood propellers by shattering the tips and elongating hub bolt holes.

See article at Old Machine Press about this engine.

From Old Machine Press

Harold Caminez went on to do detailed design work on the Allison V-1710 V-12 engine in the early and mid-1930s, invented the Heli-Coil in the mid-1930s, and helped design the Lycoming XH-2470 H-24 and XR-7755 IR-36 engines in the late 1930s and early 1940s. On 28 July 1943, he and 19 others were killed in the crash of American Airlines Flight 63. Caminez was on a business trip for Lycoming when the Douglas DC-3 went down due to weather west of Trammel, Kentucky.

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Note the three bladed propeller in the following photo.

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