Fun Fact
The first documented pulley machine was the block and tackle pulley system developed by Archimedes.
A sheave is simply a pulley for hoisting that has a grooved rim for guiding the wire used for lifting. They are found in various styles of cranes and lifting equipment. Sheaves are often made of metal, but plastics, particularly nylon, can be a better choice as they cause less abrasion of the wire or rope.
