A pneumatic jackhammer, also known as a pneumatic drill or pneumatic hammer, is a jackhammer that uses compressed air as the power source. The air supply usually comes from a portable air compressor driven by a diesel engine. Reciprocating compressors were formerly used. The unit comprised a reciprocating compressor driven, through a centrifugal clutch, by a diesel engine. The engine’s governor provided only two speeds:

1.idling, when the clutch was disengaged

2.maximum, when the clutch was engaged and the compressor was running