4. The layout and dimensions of a double shoe brake is shown in figure. The diameter of the brake drum is 300 mm and the contact angle is 90 degrees. If the coefficient of friction for the brake lining and the drum is 0.4 find the spring force necessary to transmit a torque of 30 Nm. Also determine the width of the brake shoes if the braking pressure should not exceed 0.28 MPa. (98.1 N and 5 mm) Assume the effective coefficient of friction ' 4μ sin 20+sin 20 RN S Ft Fulcrum Ft 250 mm R 225 mm