Brake Drum Design

The design or capacity of a brake depends upon the following factors:

1. Pressure between the braking surfaces
2. Coefficient of friction
3. Velocity of the brake drum
4. Projected area
5. Heat dissipation rate

Materials for Brake Lining

The material used for the brake lining should have the following characteristics:

1. High coefficient of friction
2. Low wear rate.
3. High heat resistance.
4. High heat dissipation capacity.
5. Low coefficient of thermal expansion.
6. Mechanical strength.
7. Moisture and oil resistant.

Specification

• max Pressure (p)=1.75 MPa
• Coefficient of friction= 0.2
• diameter of the brake=240mm
• Face width of the brake=30mm
• a(the distance from center to the hinged shoe)=100mm
• Allowable stress of cast iron=276 MPa
  e = the perpendicular distance from the actuating force to the hinged point (78+100cos24 = 169.35mm)
• θ₁=0°=0 rad
• θ₂=132°=2.303radWhere, n &m are constant dimensionless characteristics of the shoe.

• Then we are going to identify the maximum pressure of brake sidesLeft side
• ∆= –1 because the brake shoe is internal
• δ= +1 because in the left side brake is trailing shoe
• The actuating moment at the bottom of the hinged(M)
• e=the perpendicular distance from the actuating force to the hinged point

e=78+100cos24=169.35mm

Let the applied force is 1N

M_L=F*e=1N*169.35mm = 169.35N

Where, No is pressure parameter.

• The maximum pressure in the left shoe

Next we will calculate the maximum pressure on the right shoe.

Right shoe

• Δ= –1 because the brake shoe is internal
• δ= –1 because in the left side brake is leading shoe

• The actuating moment at the bottom of the hinged(M)Mr=F*e=1N*169.35mm=169.35Nmme is the same with the left shoe

The maximum pressure in the right shoe

Then the maximum pressure required for the 1N applied force is in the right side Pmax=0.4401kpa.

This pressure is less than the maximum limit pressure (1.75Mpa); therefore our design is safe.

Next we will require the applied force formed by the Pmax

Then by cross multiplication the applied force becomes

Over all braking torque

For left shoe

Where, No in the maximum Force applied

Right shoe

Stress on the brake drum

• D=diameter of the drake drum
• W=face width of the brake drum
• δh=stress