Engine, Caminez Radial X-4

Type: Reciprocating, 4 cylinders, radial, air cooled

Power rating: 101 kW (135 hp) at 1,000 rpm

Displacement: 7.3 L (447 cu in.)

Bore and Stroke: 144 mm (5.6 in.) x 114 mm (4.5 in.)

Weight (dry): 164 kg (360 lb)

Before forming the Fairchild-Caminez Engine Corporation in 1925, Harold Caminez used parts from other engines to build and test a model of his unconventional engine at the U.S. Army’s McCook Field in Dayton, Ohio. The reciprocating motion of the pistons was converted into rotary motion by means of rollers operating on a double-lobed cam on the main shaft. The two lobes of the cam caused each piston to make four strokes, or one complete cycle, during each revolution of the main shaft, resulting in a greater output at any shaft speed for a given cylinder displacement. This gave the effect of a 2 to 1 reduction drive for the propeller, eliminating the need for cam gearing.

Although the concept showed promise, it required a large four-bladed propeller. It did pass government tests, but vibrated excessively due to imbalance and broke down because of inaccurate machining of some parts.