What is Crankshaft? and how it works? parts of crankshaft, types, its function, and more explained with diagrams. Download the PDF Learn about the crankshaft, a shaft that converts reciprocating motion to rotary motion or vice versa. Find out the types, diagram, function, material, design procedure and stresses of crankshaft. Learn what a crankshaft is, how it works, and what parts it has. A crankshaft is a mechanical part that transforms the piston's reciprocating motion into rotary motion and turns the vehicle wheels. The crankshaft is the first rotating component in a reciprocating engine that is driven by a single or multiple reciprocating pistons. It is also found in several applications that involve the conversion between rotating and reciprocating motion.