The crankshaft, regarded as the "backbone" of the engine, serves to change the reciprocating motion of the piston into rotary motion and handles the entire power output.

The torsional vibration absorbers of reciprocating piston engine crankshafts are the earliest and most commonly used kind of damped dynamic vibration absorbers.

Reciprocating piston pump crankshaft by connecting rods connected with the original motivation. Prime mover can be motor, steam engine can also be used.