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A pulley wheel is a round object, usually made of durable materials, that is used for a variety of applications, the most common of which include lifting objects or guiding belts, chains, and ropes. The pulley wheel features an axle that is typically mounted to a frame or brace that allows the wheel to rotate freely. This reduces friction when a rope, chain, or belt is run around the pulley. The outer edge of the pulley can be grooved to help guide the belts, ropes, chains, or cables, preventing them from slipping off the pulley during operation.
The applications of a pulley wheel can vary significantly, and the size of the wheel will often vary according to the purpose for which it is being used. A pulley wheel can, for example, be used in an automobile engine compartment to help guide the timing belt or the serpentine belt, and the wheel can also be used to power peripheral devices such as power steering units and air conditioners. These wheels will be fairly small. By comparison, an exceptionally large pulley wheel may be used on a ski lift at a ski area. This large pulley wheel will help guide the cable on which the chairs are secured, and it will help keep proper tension on the cable.
Warehouses and factories often use pulley wheels as part of a system to help lift and/or move heavy objects. A rope or cable can be strung through one or more pulleys, and one end of the cable can be affixed to the object that needs to be moved. Adding pulleys to the system will decrease the amount of effort needed to lift the object, though this can also add friction to the system, thereby making movement more difficult. The right balance of pulleys must be found to effectively lift or move the objects. Many of these pulley systems are motorized to help move items more quickly and to lift exceptionally heavy items.
The materials used to make a pulley wheel can vary according to the purpose for which the wheel will be used. For light duty systems, a nylon or plastic pulley may be sufficient, though for heavier duty applications, a harder, more durable material will be necessary. Pulleys used in automobile engines are usually made from heat resistant metals that will not wear out quickly or easily during constant exposure to high temperatures and regular use.