Estimate the brake torque in Problem 18.24 using long-shoe equations.
Problem 18.24
Figure P18.24 shows a brake with one shoe (a second shoe would normally be used to balance the forces, but only one shoe is shown here to keep the problem short). The width of shoe contact with the drum is 40 mm. The friction material provides a coefficient of friction of 0.3, and permits an average pressure of 600 kPa, based on the projected area of contact. Use the short-shoe approximate relationships. The initial drum speed is 1200 rpm.
(a) What value of force F can be applied without exceeding the allowable contact pressure?
(b) What is the resulting brake torque?
(c) Is the brake self-energizing or deenergizing for the direction of rotation?
(d) What radial force is applied to the pivot bearing at point A?
(e) If full application of the brake brings the drum from 240 rpm to a stop in 6 seconds, how much heat is generated?
(f) What is the average power developed by the brake during the stop?
