we present a conventional analysis that has long been used for the belt drives. Note that a number of theories describe the mechanics of the belt drives in more detailed mathematical form (1-5), Figure 13.5a illustrates the usual belt drive, where the belt tension is such that the sag is visible when the belt is running. The friction force on the belt is taken to be uniform throughout the entire are of contact. Due to friction force on the belt is taken driver pulley, the tight-side tension is greater than the slack-side tension. Referring to the figure, the following basic relationships may be developed.