In a belt driven pulley a continuous belt joins two pulley wheels. The wheel to which an external
force is applied (effort) is called the drive wheel, and the other the driven wheel. The drive pulley
wheel provides the input force and the driven pulley wheel delivers the output force. When the
drive wheel turns the belt moves and causes the driven wheel to turn in the same direction. If the
drive wheel is smaller than the driven wheel, the driven wheel will turn more slowly than the drive
wheel.
Belt driven pulleys rely on belt friction to transmit motion. If the belt is too tight the belt will create
wasteful friction forces on the pulley axle and bearing. If too loose the belt will slip and the effort
is not used efficiently. Slip is an overload protection safety feature of belt-operated machinery.
For heavy lifting jobs; multiple pulley wheels can be combined into a lifting system that makes
lifting heavy objects easier.