Belt and pulley systems can be used to reduce speed. Higher horsepower engines run at speeds between 1000 to 3600 RPM (revolutions per minute). The machines of these power motors generally operate at half these speeds or less. The solution to this situation is to place a small pulley on the motor and a larger one on the machine that is being driven by the motor. When a small pulley drives a large pulley, a reduction in speed occurs.
Check drive speed
Determines the speed of the drive motor and the required speed of the driven equipment. For example: if the normal speed of the engine is 1800 RPM, then that is its speed. If the equipment that the engine will be driving operates at a normal speed of 900 RPM, then that is the required drive speed.
Divide the driven speed by the motor speed to get the pulley ratio. For example, 900 RPM divided by 1800 RPM equals 0.5. The pulley ratio is also equal to the diameter of the motor pulley divided by that of the driven pulley. This means that to obtain a reduction in speed, the driven pulley must be twice the size of the motor pulley.
Place a 2-inch (5.08-centimeter) pulley on the motor shaft and place a 4-inch (10.16-centimeter) pulley on the shaft of the driven machine. Connect the two pulleys with a new belt and tighten the belt to the necessary tension.
