What’s a Serpentine Pulley?

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Serpentine pulleys transfer mechanical power from a motor to other devices using a serpentine drive belt. They can be smooth or grooved and are used for movement, powering accessories, or providing tension. Grooves increase gripping force and allow for more complex systems.

A serpentine pulley is a component that can be used to transfer mechanical power from one source, such as a motor, to another device. To facilitate this power transfer, a serpentine drive belt can be passed around two or more pulleys. As the drive pulley rotates, the serpentine belt transfers that motion to the accessory pulleys. A serpentine pulley can be smooth or have a number of grooves, depending on the amount of slippage allowed in a given system. Some systems have both smooth and grooved serpentine pulleys, in which case the belt will have one grooved side and one plain side.

The three main types of serpentine pulleys are used to provide movement to a system, to power accessories, or to provide tension. Drive pulleys typically have the heaviest construction of the three and often include a harmonic balancer in automotive applications. Accessory pulleys can be smooth or grooved and exist to use the motion of a serpentine belt to power various devices. Idler pulleys are usually needed to ensure that the belt does not slip. Depending on the configuration of a system, a tensioner pulley could also be plain or grooved.

Grooves are typically added to create additional gripping force between a serpentine pulley and the belt. The number of grooves on the pulley, which can vary from three to six or more, corresponds to the same number of grooves on a belt. The grooves on a serpentine belt fit into those on a matching pulley, so the comparative contact area between the two is greatly increased on a plain belt. This can allow a strap to have more gripping force without needing more tension. Most serpentine belts tend to have one smooth side and one grooved side, although others have two grooved sides.

The main advantage of a serpentine pulley over V-belt pulleys or other pulleys is the complexity of the systems that can be created using them. Both sides of a serpentine belt can be used to drive accessory pulleys, which can result in snake-like designs. In this way, a single serpentine belt can be routed around the pulleys for many accessory devices, saving a lot of space in a plant design. This can be especially important in applications where space is at a premium, such as automobile engines. In other cases, the greater design simplicity may be desirable due to cost concerns.




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