Question 13.9: Design of a Short-Shoe Drum Brake The brake shown in Figure ...
Design of a Short-Shoe Drum Brake
The brake shown in Figure 13.21 uses a cork lining having design values of f = 0.4 and p_{max} = 150 psi. Determine
a. The torque capacity and actuating force
b. The reaction at pivot A
Given: a = 12 in., w = 3 in., b = 5 in., c = 2 in., r = 4 in., \phi = 30°
a. From Equation 13.47, we have
F_n=p_{\max }\left[2\left\lgroup r \sin \frac{\phi}{2}\right\rgroup \right] w (13.47)
F_n=150\left[2\left\lgroup 4 \sin \frac{30^{\circ}}{2}\right\rgroup \right] 3=931.7 lb
Equation 13.48 yields
T=f F_n r (13.48)
T=(0.4)(931.7)(4)=1.491 kip \cdot in .
Applying Equation 13.49,
F_a=\frac{F_n}{a}(b-f c) (13.49)
F_a=\frac{931.7(5-0.4 \times 2)}{12}=326.1 lb
b. The conditions of equilibrium of the horizontal (x) and vertical (y) forces give
R_{A x}=931.7(0.4)=372.7 lb , \quad R_{A y}=605.6 lb
The resultant radial reactional force is
R_A=\sqrt{372.7^2+605.6^2}=711.1 lb