BAND AND BLOCK BRAKE
The band brake may be lined with blocks of wood or other material. The friction between the blocks and the drum provides braking action. Let there are ‘n’ number of blocks, each subtending an angle 2 θ at the centre and the drum rotates in anticlockwise direction.
Consider one of the blocks (say first block). This is in equilibrium under the action of the following forces :
1. Tension in the tight side (T1),
2. Tension in the slack side (T1') or tension in the band between the first and second block,
3. Normal reaction of the drum on the block (RN), and
4. The force of friction (µ.RN).
Resolving the forces radially, we have
1. Tension in the tight side (T1),
2. Tension in the slack side (T1') or tension in the band between the first and second block,
3. Normal reaction of the drum on the block (RN), and
4. The force of friction (µ.RN).
Resolving the forces radially, we have
Resolving the forces tangentially, we have
Dividing above equations
Similarly it can be proved for each of the blocks that
Braking torque on the drum of effective radius re,