Crankshaft 

A crankshaft is a crankshaft that is applied to the transmission of machinery, metallurgy, equipment, internal combustion engines, etc.. It is a mechanical part able to perform a conversion between reciprocating motion and rotational motion. 

It is typically connected to a flywheel to reduce the pulsation characteristic of the four-stroke cycle, and sometimes atorsional or vibrational damper at the opposite end, to reduce the torsional vibrations often caused along the length of the crankshaft by the cylinders farthest from the output end acting on the torsional elasticity of the metal.