Pulleys are simple machines consisting of a wheel with a pulled chain, driving belt, or rope that runs through it. Pulleys can help you lift large weights. Some say the are among the most useful tools ever invented!
If you need to lift a heavy weight, using a simple machine like a pulley can multiply the force applied and make lifting easier.
Belt sheaves are part of a belt and pulley system and are made of two or more sheaves working together, using a belt instead of wires or ropes. The sheaves are generally different diameters, which assist in moving the belt faster with far less effort. Belt sheaves are constructed like a chain drive, but instead of having cogs, they are smooth.