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 rotating part, though many small engines, such as those found in garden machinery, use only a single piston. The configuration of pistons in relation to each other and the crank and their number leads to descriptions such as straight-4
(four pistons in direct line), V6
In the Wankel engine, the rotors drive the eccentic shaft, which can be considered the equivalent of the crankshaft in a piston engine.