Belts:
In case of belts, friction among the belt and pulley is utilized to transmit power. In practice, there is always some amount of slip among belt and pulleys, thus, exact velocity ratio may not be obtained. That is why; belt drive is not a positive drive. Hence, the belt drive is utilized where exact velocity ratio is not needed.
The following kinds of belts illustrated in given figure are most commonly utilized :
(a) Flat Belt and Pulley (b) V-belt and Pulley (c) Circular Belt or Rope Pulley
The flat belt is rectangular in cross-section as illustrated in Figure (a). The pulley for this belt is slightly crowned to avoid slip of the belt to one side. It uses the friction among the flat surface of the pulley and belt.
The V-belt is trapezoidal in section as illustrated in Figure (b). It uses the force of friction among the inclined sides of the pulley and belt. They are preferred while distance is comparative shorter. Various V-belts can also be utilized together if power transmitted is more.
The circular belt or rope is circular in section as illustrated in Figure (c). Various ropes also can be utilized together.
The belt drives are of the following kinds :
(1) Open belt drive, and
(2) Cross belt drive.