The Semi-centrifugal clutch uses centrifugal force as well as spring force for keeping it in the engaged position. The springs are designed to transmit the torque at normal speeds, while the centrifugal force assists in torque transmission at higher speeds.
The figure shows a semi-centrifugal clutch. It consists of three hinged, weighted levers and three clutch springs alternately arranged at equal spaces on the pressure plate.
At normal speeds, when the power transmission is low, the springs keep the clutch engaged, the weighted levers do not have any pressure on the pressure plate. At high speed, when the power transmission is high, the weights fly off and the levers also exert pressure on the plate, keeping the clutch firmly engaged.
Thus, instead of having more stiff springs for keeping the clutch engaged firmly at high speeds, they are less stiff, so that the driver may not get any strain in operating the clutch.
When the speed decreases, the weights fall and the levers do not exert any pressure on the pressure plate. Only the spring pressure is exerted on the pressure plate which is sufficient to keep the Semi-Centrifugal clutch engaged.
An adjusting screw is provided at the end of the lever, by means of which the centrifugal force on the pressure plate can be adjusted. The lever is shown in details in the figure.
For better understanding about Semi-Centrifugal Clutch watch the video below
- Less stiff springs used for keeping the clutch engaged.
- Less Driving effort is required to operate the Semi-Centrifugal clutch.
- Only during high speed, the clutch has sufficient force to be in the engaged position.
- At low speeds, less force is exerted on the pressure plate by the springs to keep the Semi-Centrifugal clutch engaged.