What does a crankshaft do?

In reciprocating engines and pumps (e.g. in piston engines), the crankshaft converts the reciprocating motion of the pistons into rotary motion.

Connecting rods attached to the pistons act on the crank pins, which are set at 90° to each other. As the piston moves up and down, it pushes and pulls on the connecting rod, which causes the crank pin to rotate. The crank pins are connected to the main shaft of the crankshaft, which is supported by the engine block.

The rotation of the crankshaft then drives other components of the engine, such as the camshaft and oil pump.