Problem 169 is preliminary to analyzing the brake. A rigid molded non-asbestos lining is used dry in the brake of Prob. 169 on a cast

Problem 16–9 is preliminary to analyzing the brake. A rigid molded non-asbestos lining is used dry in the brake of Prob. 16–9 on a cast iron drum. The shoes are 6 in wide and subtend a 90◦ arc. Find the maximum allowable actuation force and the braking torque.

Problem 16–9, the shoes on the brake depicted in the figure subtend a 90◦ arc on the drum of this external pivoted-shoe brake. The actuation force P is applied to the lever. The rotation direction of the drum is counterclockwise, and the coefficient of friction is 0.30.

(a) What should the dimension e be?
(b) Draw the free-body diagrams of the handle lever and both shoe levers, with forces expressed in terms of the actuation force P.
(c) Does the direction of rotation of the drum affect the brakingtorque?

12 130 130 1O R 12 20 20 Shoe 61 15.28 13.5 7.78