# Types of Flat Belt Drive and Pulleys

## Types of Flat Belt Drive:

1. Open Belt Drive: The open belt drive is used with shafts arranged parallel and rotating in the same direction. In this case, the driver A pulls the belt from one side and delivers it to the other side. Thus, the tension in lower side belt will be more than that in the upper side belt. The lower side belt is known as tight side whereas the upper side belt is known as slack side.

2. Crossed Belt Drive: The crossed or twist belt drive is used with shaft arranged parallel and rotating in the opposite directions. In this case, the driver pulls the belt from one side and delivers it to the other side. Thus the tension in the belt RQ will be more than that in the belt LM. The belt RQ is known as tight side, whereas the belt LM is known as slack side.

3. Quarter-Turn Belt Drive: The quarter turn belt drive also known as right angle belt drive is used with shafts arranged at right angles and rotating in one definite direction. In order to prevent the belt from leaving the pulley, the width of the face of the pulley should be greater or equal to 1.4, where b is the width of belt.

4. Compound Belt Drive: A compound belt drive is used when power is transmitted from one shaft to another through a number of pulleys.

## Types of Flat Belt Pulleys:

1. Belt Drive with Idler Pulleys: A belt drive with an idler pulley is used with shafts arranged parallel and when an open belt drive can’t be used due to small angle of contact on the smaller pulley. This type of drive is provided to obtain high velocity ratio and when the required belt tension can’t be obtained by other means.

2. Steeped or Cone Pulley Drive: A stepped or cone pulley drive is used for changing the speed of the driven shaft while the main or driving shaft runs at constant speed. This is accomplished by shifting the belt from one part of the steps to the other.

3. Fast and Loose Pulley Drive: A fast and loose pulley drive is used when the driven or machine shaft is to be started or stopped when ever desired without interfering with the driving shaft. A pulley which is keyed to the machine shaft is called fast pulley and runs at the same speed as that of machine shaft.

A loose pulley runs freely over the machine shaft. It is incapable of transmitting any power. When the driven shaft is required to be stopped, the belt is pushed on to the loose pulley by means of sliding bar having belt forks.