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  • Writer's pictureSyed Sagheer Abbas Rizvi

Everything You Need to Know About Variable Speed Pulleys

A Variable Speed Pulley is equipment used to adjust the speed of a rotating shaft member, increasing or decreasing the number of revolutions the shaft makes each minute. The belt used in the pulley has a "V" cross-section, with the sides fitting snugly against the angular pulley flange faces.

The belt will be driven up or down in the pulley when the flanges open or shut. This will result in a bigger or lower working pitch diameter, which will in turn affect how many revolutions per minute the shaft is turning, upon which the pulley is placed.

Two pulleys are often mounted on two distinct shafts, one of which is the drive shaft and is always the source of power, such as an electric motor, and the other of which is the driven shaft and is the component that needs the speed variation.

Simply put, the belt serves as a conduit for the passage of energy from the power source to the driven object. The frictional grip, which is the belt acting as a wedge between the pulley faces, allows the belt to transmit power.

Variable-speed pulleys are employed in a vast range of applications, from tractors to heavy equipment. But how do pulleys with changing speeds operate?

Variable Speed Pulleys

Understanding what variable speed pulleys are supposed to perform is the first step in learning how they operate. A variable speed pulley's function is to adjust the speed of a spinning shaft. It is possible to either raise (speed up) or reduces the number of rotations per minute (slowed).

Two pulleys are needed for the drive

: a fixed diameter pulley positioned on the driven shaft and a variable speed pulley mounted on the driving shaft.

The driven shaft is the one that needs a speed change, while the drive shaft acts as the power supply, similar to a motor. The power is transferred from the drive shaft to the driven shaft using a belt.

The variable speed pulley has one or two movable flanges, which is how it operates. The force of the spring keeps the flange closed.

There are 2 types of variable speed pulley systems.

Movable shaft center distance:

The belt causes the variable speed pulley to open as the motor, which is mounted on an adjustable motor base, is adjusted to increase the center distance between the two shafts.

The belt can travel from the maximum pitch diameter (PD) to the minimum pitch diameter (PD), or any place in between, when the two flanges separate.

Fixed shaft center distance:

A variable-speed pulley is positioned on the driving and driven shafts at a fixed shaft center distance. The drive pulley is mechanically opened or closed depending on the required rpm, whilst the driven pulley is adjustable.

The speed of the driven pulley will change depending on whether the drive pulley is opened or closed; the driven pulley will speed up as the drive pulley is closed.

Within the bounds of normal ratios, the speed range of variable-speed pulleys is almost limitless.

Our pulleys are built to provide a cost-effective solution for many applications that may not require the expense of AC/DC variable speed motors and controllers. They are designed for belt diameters ranging from 1/4" V to 5/8" V and horsepower ratings ranging from 1/12 HP to 1.0 HP.


Wanfu Group can obtain a variety of these essential industrial components, like variable speed pulleys and belts, if you're trying to find something in particular. Visit our website page for additional details on the many brands of variable speed pulleys and belts.

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