The figure shows a band brake designed to prevent “backward” rotation of the shaft. The angle of wrap is 270◦, the band width is 2 1/8 in, and the coefficient of friction is 0.20. The torque to be resisted by the brake is 150 lbf . ft. The diameter of the pulley is 8 ¼ in.
(a) What dimension c1 will just prevent backward motion?
(b) If the rocker was designed with c1 = 1 in, what is the maximum pressure between the band and drum at 150 lbf ?ft back torque?
(c) If the back-torque demand is 100 lbf . in, what is the largest pressure between the band and drum?