Piston

A partly hollow, cylindrical plug that fits closely inside the bore of the engine cylinder. It is connected to the crankshaft via the connecting rod and fitted with rings to seal it in the cylinder.

As the piston moves inside the cylinder, it transforms the energy from the expansion of a burning gas into mechanical power. From there the power is conveyed through a connecting rod to a crankshaft, which transforms the reciprocating linear motion into a rotary motion, which then drives the gearbox.