What is "cam engine"

A cam engine is a reciprocating engine where, instead of the conventional crankshaft, the pistons deliver their force to a cam that is then caused to rotate. The output work of the engine is driven by this cam.

Cam engines have been a success. The first engine to get an airworthiness certificate from the United States government was, in fact, a radial cam engine. A variation of the cam engine, the swashplate engine (also the closely related wobble-plate engine), was briefly popular.

These are generally thought of as internal combustion engines, although they have also been used as hydraulic- and pneumatic motors. Hydraulic motors, particularly the swashplate form, are widely and successfully used. Internal combustion engines, though, remain almost unknown.