crank throw

A crank throw is a mechanical component that converts reciprocating motion into rotary motion, or vice versa. It is a key part of the slider-crank mechanism, commonly found in engines and pumps.1

In a gasoline engine, the connecting rod attaches the piston to an offset portion of the crankshaft, known as the throw. This connection allows the piston's back-and-forth movement to turn the crankshaft. The radial displacement from the crankshaft's center to the crankpin center defines the crank throw. The length of the piston stroke is determined by this radial offset, which is half the stroke imparted to the piston. Counterweights are often added to the crankshaft to balance the eccentric mass of the crank throws, improving engine stability.23