The rotation motion is the ideal and the simplest means of transmission of mechanical power with negligible losses. Rotational motion can be transmitted from one mechanical element to the other with the help of certain systems known as transmission systems or drives.
These systems are driven by a prime mover or transmit the rotational motion to the various parts of a machine within itself. Usually, shafts are employed to transmit rotational motion.
The one that drives is called the driving system and
The other which is driven is called driven system.
Belt Drives are a type of frictional drives used for transmitting powers from one shaft to another by means of pulleys which rotate at the same speed or at the different speed.
Belt drive types
A belt drive is shown in the figure. It consists of two pulleys over which an endless belt it passed over them. The mechanical power or rotary motion is transmitted from the driving pulley to the driven pulley because of the frictional grip that exists between the belt and the pulley surface.
The portion of the belt which is having less tension is called slack side and the one which has higher tension is called tight side. The effective pulling power of the belt that causes the rotation of the driven pulley is the difference in tension on the slack and tight side.
The tensions in the tight and slack sides of the belt depend on the angle of contact, the belt drives have to be arranged such that the slack side comes above and the tight side comes below the pulleys.
This arrangement increases the angled contact of the belt on the driven side. Sometimes in a belt-drive, there is always a possibility of some slipping taking place between the belt and the pulleys which cause the driven pulley to rotate at a lesser speed, consequently reduces the power transmission. Hence belt drives are said to be not a Positive type of power transmission system
Types of Belts
There are four commonly used types of belts are:
Flat belt: This belt has a rectangular cross-section. These belts are capable of transmitting power over long distances between pulley centres. The efficiency of this drive is around 98% and produce little noise.
V-belts: v-belts also used with grooved pulleys, V-belts are trapezoidal in cross-section. These belts permit large speed ration and can transmit higher power. Multiple drives are possible.
Circular: This type of belt has a circular cross-section and is used with the grooved pulleys.