Semi Centrifugal Clutches used in high powered engines and racing car engines where clutch disengagements require appreciable and tiresome drivers effort. The power transmitted with partly by clutch springs and remaining by the centrifugal action of an extra weight provided in the system.
The clutch springs transmit power at low engine speed and the centrifugal force transmit power at higher engine speed.
Construction of Semi Centrifugal Clutch
Besides clutch, pressure plate and splines shaft it mainly consists of:
- Compression spring (3 numbers)
- Weighted levers (3 numbers)
Working of Semi Centrifugal Clutch
When the engine at low speed the spring keeps the clutch engaged to transmit power, the weighted levers do not have any pressure on the pressure plate.
When engine at high speed the weights fly off and levers exert pressure on the pressure plate which keeps the clutch firmly engaged to transmit high torque.
Thus instead of having more stiff springs for keeping the clutch engaged firmly at high speeds, they are less stiff because of centrifugal forces of weighted levers, so that the driver may not get any strain in operating the clutch.
when the engine speed decreases, the weights fall and the weighted levers do not exert any pressure on the pressure plate and only spring pressure is exerted on the pressure plate to keep the clutch engaged.
- Clutch operation is very easy.
- Less stiff clutch springs are used as they operate only at low engine speeds.
- Springs have transmitted the torque at lower engine speeds only.
- Centrifugal forces work only at higher engine speed to transmit torque.
- Semi Centrifugal Clutch is used in Vauxhall car (foreign car).