Crankshaft

The crankshaft is that part of an engine which translates linear piston motion into rotation. Generally more than one piston is attached to the crank to provide a smoother delivery of power to the rotation cycle, though many small engines use only a single piston, such as those found in garden machinery. The configuration of pistons in relation to each other and the crank and their number leads to descriptions such as [straight eight]? eight pistons in direct line, V12 twelve pistons alternately angled, [diametrically opposed five]? five pistons with three set diagonally opposed to two.

In the Wankel engine, the crankshaft and the chamber in which it rotates is shaped to provide a compression and expansion area allowing the forces caused by detonation of the fuel to act directly on the crankshaft.