# Centrifugal clutch - contact between shoe friction lining & drum surface - Theory of Machines - 1

Q.  In centrifugal clutches, when is the contact between shoe friction lining and surface of drum observed?
- Published on 06 Aug 15

a. When centrifugal force is less than spring force
b. When centrifugal force is equal to spring force
c. When centrifugal force is greater than spring force
d. None of the above

ANSWER: When centrifugal force is equal to spring force

#### Discussion

• Sravanthi   -Posted on 19 Oct 15
- The principle of centrifugal force is used in centrifugal clutches.

- As speed increases centrifugal force increases and this force is required to engage driven member automatically after driving member has attained particular speed.

- Centrifugal clutch consists of spider, sliding shoe, drum, input and output shaft and helical tension spring.

- The helical tension springs keep the shoes against the spider on driving shaft and this assembly is enclosed in coaxial drum.
- Centrifugal force acting on the shoe is less than inward radial force when speed of driving shaft is low. Hence shoe friction lining and inside surface of drum have no contact between them. But when spring force is equal to centrifugal force shoe starts floating and there exists contact between inner surface of the drum and shoe.

- If speed of shaft increases, centrifugal force is greater than spring force and the shoe is pressed against the inside surface of the drum.

- Because of friction force between drum surface and shoe lining, torque is transmitted from driving shaft to driven shaft.

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