Pulley

(design engineering) A wheel with a flat, round, or grooved rim that rotates on a shaft and carries a flat belt, V-belt, rope, or chain to transmit motion and energy.

A wheel with a flat, crowned, or grooved rim used with a flat belt, V-belt, or a rope to transmit motion and energy. Pulleys for use with V-belt and rope drives have grooved surfaces and are usually called sheaves. A combination of ropes, pulleys, and pulley blocks arranged to gain a mechanical advantage, as for hoisting a load, is referred to as block and tackle. See also Belt drive; Block and tackle.

Pulleys for flat belts are made of cast iron, fabricated steel, wood, and paper. A particular pulley design must be based on such considerations as the ability to resist shock, to conduct heat, and to resist corrosive environments. The face must be smooth enough to minimize belt wear; yet there must be adequate friction between belt and pulley face to carry the load.

The two common types of V-belt pulley are pressed-steel and cast-iron. The pressed-steel pulleys are suitable for single-belt drives. For multiple-belt drives, or in single-belt drives where pulley mass should be high to get a flywheel effect, cast-iron pulleys are used.