A short shoe external drum brake is shown in the figure. The diameter of the brake drum is 500 mm

Q. A short shoe external drum brake is shown in the figure. The diameter of the brake drum is 500 mm. The dimensions a = 1000 mm, b = 500 mm and c = 200 mm. The coefficient of friction between the drum and the shoe is 0.35. The force applied on the lever F = 100 N as shown in the figure. The drum is rotating anti-clockwise. The braking torque on the drum is________N·m (round off to two decimal places).

Ans: 20.35

Sol:

By considering the moment about point ‘O’

F×a=N×b−μN×c

100×1000=N×500−0.35N×200

N=232.558 Newton

Braking torque =μN×D2

=0.35×232.558×500/2×10⁻³

=20.35 Nm