Brake drum, commonly known as brake drum, is one of the key parts in the automobile braking system. It is a friction coupling part of the drum brake. It should not only have the required strength and stiffness as a component, but also have high and stable wear resistance, heat resistance, heat dissipation and heat capacity.

A, classification,

The basic shape of the brake drum is drum type, and there are connecting holes on the mounting surface

1. Whole casting type

Brake drum is made of high strength gray cast iron or alloy cast iron containing Cr. This kind of brake drum has the advantages of simple structure, convenient processing, large heat capacity, but large mass, and is mostly used in medium and heavy duty vehicles

2. Combined steel plate and cast iron

Brake drum is composed of steel plate stamping drum plate and cast iron drum ring, the mass is small, more used in cars and light vehicles

3. Light alloy combined with cast iron

The main body of the brake drum is light alloy material (such as aluminum alloy, etc.), lined with cast iron bushing. This kind of brake drum is not only small in mass, but also good in heat dissipation. It is mostly used in cars

Two, brake drum requirements

Improper design of brake drum, which is changeable when heated; Brake drum force is not balanced, will also produce mechanical deformation, so that the hooves and drum contact is poor, resulting in pedal force and stroke increase; When the unroundness of the working surface of the brake drum is too large, it will also cause self-locking and vibration and noise. Therefore, the brake drum should have sufficient wall thickness, and cast circumferential or axial stiffeners near the opening on the outer surface to improve the strength. These reinforcing bars also play the role of heat dissipation, can reduce the temperature of the friction surface, shorten the cooling time of the brake, so that the energy capacity is increased. The wall thickness of the brake drum is mainly considered from the aspects of stiffness and strength. The wall thickness of the brake drum generally cast is 7-12mm for cars and 13-18mm for medium and above trucks. The wall thickness is larger to help increase the heat capacity.

Brake drum maintenance

Brake drum due to frequent braking in car driving, easy to cause hot and cold alternation, easy to wear, cracking, cracking, regular inspection and maintenance is very important, must be repaired and replaced in the following circumstances:

1. If the diameter of the brake drum exceeds the scrap size or does not exceed the scrap size, but after cutting, the diameter of the brake drum exceeds the safety repair size, it should be replaced.

2. Brake drums with taper or roundness error exceeding 155μm should be replaced.

3. When hard points occur due to changes in metallographic structure caused by braking heat on the friction surface of brake drum, it should be replaced.

4. The brake drum should be replaced when there is any crack.