Question

The maximum actuating force on a double short shoe external drum brake illustrated in figure 1 below is 3 kN. If the coefficient of friction for the shoe lining is 0.3. 1.1 Determine the torque capacity of the brake for clockwise rotation of the drum. (11) Hint 1: Note the distance between the shoe and the pivot is not ignorable. Hint 2: Consider both shoes in your analysis. 1.2 Draw the forces acting on each shoe. 

Answer 1

Taking moments at a point say O

$F_a*300= R_N1 *200+(150-120)\\ 2000*300= \frac{F_{t1}}{\mu}*200+30 F_{t1}\\ F_{t1}=1020.34 N$

Taking moments at a point say A

$F_a*300= F_{t2} (150-120)= R_{N_2}*200\\ 2000*300+30F_{t2}= \frac{F_{t2}}{\mu}*200\\ F_{t2}=1136.286 N$

Braking torque

$(1020.34+1136.286)150=323494.016 N$