A centrifugal clutch with four shoes is used to transmit 15 kW to 720 r.p.m. The speed at which engagement begins is 80% of full speed. The inside diameter of the drum is 325 mm and outside diameter of the drum is 350 mm. The radial distance of C.G. of each shoe from the axis of shaft is 120 mm. The radial clearance between the shoe and the rim is 10 mm. The pressure exerted on the shoe during engagement is 1.0 MPa. The coefficient of friction between shoe lining and the drum is taken as 0.25.
Determine
(i) Mass of each shoe.
(ii) Size of the shoe if the angle subtended by shoe at centre is 60°.
Also design the helical spring used in the shoes taking the safe shear stress of spring material as 600 MPa and modulus of rigidity of the material as 80 kN/mm2. Use the spring index of 6.