Example 1: If the diameter of the driving pulley D is 24 inches, its speed is 100 rpm, and the driven pulley is to run at 600 rpm, the diameter of the driven pulley, D2 = 24 x 100 / 600 = 4 inches.
Example 2: If the diameter of the driven pulley D2 is 36 inches, its required speed is to be 150 rpm, and the speed of the driving pulley D is to be 600 rpm, the diameter of the driving pulley D = 36 x 150 / 600 = 9 inches.
Example 3: If the diameter of the driven pulley D2 is 4 inches, its required speed is 800 rpm, and the diameter of the driving pulley D is 26 inches, the speed of the driving pulley = 4 x 800 / 26 = 123 rpm.
Example 4: If the diameter of the driving pulley D is 15 inches, and its speed is 180 rpm, and the diameter of the driven pulley D2 is 9 inches, then the speed of the driven pulley = 15 x 180 / 9 = 300 rpm.
