The piston engine uses the crankshaft to convert the reciprocating motion of the piston into rotary motion.
The crankshaft is used to convert reciprocating motion of the piston into rotary motion, while the conversion process is called torque, which is a twisting force. Aside from crankshaft, there are a total of four parts of the engine that work together in order to convert the reciprocating motion into rotary motion namely cylinder, or also called the chamber of the piston, the piston itself, and the connecting rod.