The crankshaft converts the up and down (reciprocating) motion of the pistons into a turning (rotary) motion. It provides the turning motion for the wheels. It works much like the pedals of a bicycle, converting up-down motion into rotational motion. The crankshaft is usually either alloy steel or cast iron. The crankshaft is connected to the pistons by the connecting-rods. Some parts of the shaft do not move up and down; they rotate in the stationary main bearings. These parts are known as journals. There are usually three journals in a four cylinder engine.

A pulley is a wheel with a groove along its edge, also called a sheave, for holding a rope or cable. Pulleys are usually used to change the direction of an applied force or in sets designed to reduce the amount of force needed to lift a load. However, the same amount of work is necessary for the load to reach the same height as would be without the pulleys. The magnitude of the force is reduced, but it must act through a longer distance. The effort needed to pull a load up is roughly the weight of the load divided by the number of wheels. The more wheels there are, the less efficient a system is, because of more friction between the rope and the wheels.

Pulleys are often included in the list of simple machines. It is not recorded when or by whom the pulley was first developed. It is believed however that Archimedes developed the first documented block and tackle pulley system, as recorded by Plutarch. Plutarch reported that Archimedes moved an entire warship, laden with men, using compound pulleys and his own strength