The firing order of an internal combustion engine is the sequence of ignition for the cylinders.
Firing order shown on a Lycoming R-680-13 9-cylinder radial engine
A crankshaft is a mechanical component used in a piston engine to convert the reciprocating motion into rotational motion. The crankshaft is a rotating shaft containing one or more crankpins, that are driven by the pistons via the connecting rods.
Crankshaft, pistons and connecting rods for a typical internal combustion engine
Marine engine crankshafts from 1942
Flying arm (the boomerang-shaped link between first and second crankpins) on a crankshaft)
Forged crankshaft