Pulley

Pulley

A pulley is a wheel on an axle or shaft that is designed to support movement and change of direction of a taut cable or belt, or transfer of power between the shaft and cable or belt. In the case of a pulley supported by a frame or shell that does not transfer power to a shaft, but is used to guide the cable or exert a force, the supporting shell is called a block, and the pulley may be called a sheave.

Types of Pulleys

Pulleys can be classified into three main types:

• Fixed Pulley: A fixed pulley has an axle that is "fixed" or anchored in place. It is a type of pulley that is used to lift heavy objects. The fixed pulley has a wheel and an axle or shaft that is supported by a frame.

• Movable Pulley: A movable pulley has an axle that is "free" to move in space. This is a pulley that has a free axle, and is used to reduce the amount of force needed to lift a load.

• Compound Pulley: A compound pulley is a combination of the simple and movable pulley. It is used to reduce the amount of effort needed to lift a load.

Uses of Pulleys

Pulleys are used in a variety of ways to lift loads, apply forces, and to transmit power. Some common places you will find pulleys are in the engine of your car, in elevators, in cranes, and in your window blinds.

History of Pulleys

The pulley is one of the six classical simple machines defined by Renaissance scientists. Pulleys are thought to have been used as far back as 1500 BC by the ancient Egyptians to lift and move large stones to build their monuments and pyramids.

See Also

• Mechanical Advantage
• Simple Machines
• Block and Tackle
• Belt (mechanical)
• Rope
• Winch
• Hoist (device)

References

Pulley Resources
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