Engine, Speco (Michell) Crankless Barrell 12

Type: Reciprocating, 12 cylinders, four stroke cycle, barrel type, liquid-cooled

Power rating: 597 kW (800 hp) at 2,500 rpm

Displacement: 34 L (2,096 cu in.)

Bore and Stroke: 158 mm (6.22 in.) x 146 mm (5.74 in.)

Weight: 2596.9 kg (1,316 lb)

This artifact was built by the Steel Products Engineering Company for the Michell-Crankless Engines Corporation, and tested by the U.S. Navy Bureau of Aeronautics. It is based on an invention of A. G. M. Michell, an Australian reciprocating engine expert. The barrel engine has a driveshaft on which is fitted an inclined disc or swashplate. Twelve cylinders are arranged radially around the driveshaft, with six cylinders on one end opposing six on the other end. The pistons act on both sides of the swashplate, and by means of almost frictionless pads, produces the rotary motion of the driveshaft. Fuel is supplied through four carburetors, two on each side. Valves are located on each side of the swashplate.

The weight and space economy of the crankless design was claimed to make it particularly well suited for application to aircraft engines. However, the Navy concluded that the performance compared unfavorably to conventional engines, and development was discontinued.