Reciprocating motion

It is found in a wide range of mechanisms, including reciprocating engines and pumps.

The two opposite motions that comprise a single reciprocation cycle are called strokes.

[citation needed][1] For example, inside an internal combustion engine (a type of reciprocating engine), the expansion of burning fuel in the cylinders periodically pushes the piston down, which, through the connecting rod, turns the crankshaft.

The continuing rotation of the crankshaft drives the piston back up, ready for the next cycle.

Additionally, if the wheel is not spinning with perfect constant rotational velocity, such as in a steam locomotive starting up from a stop, the motion will be even less sinusoidal.

Double-acting stationary steam engine demonstrating conversion of reciprocating motion to rotary motion. The piston is on the left, and the crank is mounted on the flywheel axle on the right
Machine demonstrating the conversion of rotary motion to reciprocating motion using gears. The bottom pair of gears drives the mechanism