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Q5. A single plate friction clutch with both sides effective having an outside diameter of 400 mm and an inside diameter of 160 mm, is designed to transmit 10 kW at 500 rev/min when new. In this condition the coefficient of friction between the contact surfaces can be taken to be 0.62. There are eight clutch springs each having a stiffness of 8 kN/m. The maximum wear of the clutch friction plate is limited to 1.5 mm of each contact surface.

During service, clutch plate wear takes place, the surfaces become contaminated and the power reduces.

Calculate EACH of the following:

(a) the total spring load required when the clutch is in the new condition; (8)

(b) the minimum coefficient of friction of the worn clutch if 75% of the original power can still be transmitted at the same speed. (8)

Note:

For constant pressure T = 2/3μnW ((r₁³ – r₁³)) / ((r₁² - r₂² ))

For constant wear T = μnW/2 (r₁+r₂)

n = Number of pair of surfaces in contact