Centrifugal clutches and brakes use centrifugal forces to transmit power (clutch) or to limit speed (brake). As the brakes are based on a physical principle, centrifugal clutches or brakes do not require any additional external power supply, which makes them a perfect solution for safety applications. Centrifugal clutches and brakes consist of a driving shaft. Around the driving shaft, there are flyweights mounted, which are kept on the shaft by springs. On the outer side of the flyweights there are friction pads.
The main difference between a centrifugal clutch and a centrifugal brake is in the drum: At a centrifugal clutch the drum is not fixed and will begin to turn when the engagement speed / operating speed is reached. At a centrifugal brake the outer drum is fix and cannot turn. This causes a braking force when the friction pads touch the drum. When designing and operating centrifugal brakes, there must be a special focus on braking time and maximum heat.
Standard centrifugal brakes are used to limit speed – they cannot bring a system to standstill. The basic principle is to keep a balance between the load of the driving side and the braking torque. During the operation there is a constant friction which generates heat.
Centrifugal brakes convert mechanical energy into heat, which is generated between the linings and the brake drum, and mostly heats up the latter. The temperature distribution illustrated above on a sectioned brake drum clearly shows the higher heating of the drum in the region over the flyweights. The amount of generated heat depends on various factors:
- Transmitted braking torque
- Brake speed
- Duration of the braking operation
- Size of the friction surface
- The mass of the brake drum that has to be heated