Centrifugal clutch works on the principle of centrifugal force. When driving shaft rotates at high speed, the shoes move radially outward. The outer surfaces of the shoes are covered with friction material which engages the pulley. Thus, pulley rotates with driving shaft. The engagement of shoes with pulley is shown in Figure 16.7. This type of clutch is generally used in motor pulley. The spring force resists the centrifugal force, thus prevents the engagement at lower speed.
Figure 16.7 Centrifugal Clutch
Fc = centrifugal force = mω2r
Fs = Spring force = 
where ω is the angular speed of the shaft.
Torque, T = F × R = μ (Fc − Fs) · R, where n is number of shoes.
Example 16.6: There are four shoes in a centrifugal clutch. The mass of each shoe is 10 kg and when the clutch is at rest, the force exerted by spring on shoe is 400 N. The clearance between shoe and drum surface is 4 mm. Spring constant is 40 N/mm. The distance of centre of mass of shoe from axis is 150 mm. The internal diameter of the drum is 320 mm. Coefficient of friction is 0.025; find the power transmitted by clutch at 400 rpm.
Solution:
Given: n = 4, m = 10 kg, x = 4 mm, K = 40 N/mm, μ = 0.025, N = 400 rpm
Operating radius, r1 = 150 + 4 = 154 mm
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