# Types of belt drive

### Types of belt drives in pulley systems

Belt drives are frictional drives that transmit mechanical energy on a dry surface from one shaft to another in a pulley like system.

Below are the various type of belt drives that are used alongside a pulley system:

• ### Open Belt Drive

The open belt drive is used when two parallel shaft are needed to rotate in the same direction.

When the open belt drive is in used on a widely separated shaft, the upper side of the belt must be the slack side while the lower side becomes the tight side.

If we made the upper side the slack side (in a separated shaft), sagging will occur and the contact arc will be increased.

• ### Cross Belt Drive

The cross belt drive is used when two parallel shafts are needed to rotate in the opposite direction.

However, due to the crossing nature of this belt, the belts rub against itself at a specific junction, resulting to its wearing off and eventual damage.

In order to reduce the excessive wear caused from the meeting point of the crossed belts, the shafts should be placed at an optimum distance from each other, and should be operated at low speeds.

• ### Fast and Loose Pulley Drive

A fast and loose pulley drive is often used when the driven pulley is required to be started or stopped without creating an interference with the driving pulley. Meanwhile, understand that the pulley keyed to the machine shaft is referred to as the fast pulley.

• The fast pulley runs at the same speed with that of the machine shaft.
• The loose pulley on the other hand runs freely over the machine shaft without transmitting any power.

• ### Stepped Cone Pulley Drive

The stepped cone pulley, (step or cone pulley drive), or speed cone pulley drive is a belt drive known for its speed. It consists of pulleys with different diameters located adjacent one another.

The step cone pulley drive aid in changing the speed of the driven shaft, with the driving shaft moving at a constant speed. It is able to do this by shifting the belt from one part of the steps to another.

The speed cone pulley drives are often utilized in instances where the gear or speed of the driven shaft changes frequently. For this reason, they are utilized in lathe and milling machines.

Understand that the same belt is used in the stepped cone pulley whenever there is a shift in various adjacent pulleys. This is achieved because the pulleys are of different diameters.

In its mechanism of action, a set of speed cone pulley is reversely mounted on the driven shaft. Also, the belt is appropriately wrapped around one of its pulleys pair. It is this shifting of belts from one pair of pulley to another that results in varying speeds of the driven shaft.

• ### Jockey Pulley Drive

The jockey pulleys, sometimes referred to as the idler pulleys are present in an open belt drive. They are typically seen in the steering section of a machine. You can imagine them be idle pulleys that functions to increase the angle of contact.

Note: When the angle of contact is increased in the steering, there is a subsequent increase in the transmission power of the drive.

The idle pulley is always mounted on the slack side of the belt (with a smaller pulley). This is so because the arc of contact of the belt with the driven pulley is very small which inturn results into reduced tensions of the belt.

Functionally, the jockey pulley aid in creating more angles of contact around the belt such that the belt's tension is consequently increased. This automatically provides an output of a high-velocity ratio by the belt drive.

• ### Quarter Turn Belt Drive

The quarter turn belt drives are popularly known as the right-angle belt drives.

As the name implies, they are used with shafts arranged at right angles, rotating in a specific direction.

It is worthy of note that the face width of the pulley must be greater than or equal to 1.4 b in order to prevent a misalignment of the belt on the pulley.

In some instances where a reversible speed is needed or the pulley cannot be properly arranged, then a right-angle belt drive with a guide pulley may prove useful.

• ### Compound Belt Drive

A compound belt drive is utilized when multiple shafts are present in the pulley system. As a result, they are typically used to transfer power from one shaft to another through multiple shafts.

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