Piston

In an Otto? or Diesel? engine, a pot-shaped moving part, which upper part forms an [explosion chamber]? together with a cylinder, inside of which it moves up and down, and a [cylinder head]? which functions as a lid with valves for gases.

It moves inside the cylinder to transform the expansion energy of an exploding gas (usually a mixture? of petrol or [diesel fuel]? and air) into mechanical energy (a linear? motion). From there it is conveyed through a rod? towards a crankshaft, transforming it into a rotational motion, usually driving a gearbox?.