Sectioned working model of a single-cylinder diesel engine, made by the National Gas & Oil Engine Co. Ltd, Ashton-under-Lyne, c.1930.

This engine has its side cut away so its workings can be seen. It was made by the National Gas & Oil Engine Company of Ashton-under-Lyne near Manchester. It is a four stroke diesel, in which the piston goes down and air enters the cylinder. The piston then rises and compresses the air which has become hot. A spray of fuel is then injected into the hot cylinder; the fuel ignites and the gases push the piston down as the power stroke. As the piston rises again, the burnt gases are emitted as exhaust and the cycle begins again.