The drum brake is kind of braking system that consists of a drum like structure called the brake drum. The system uses a set of shoes or pads against the brake drum to cause friction and thus braking. The drum brake system is very similar to the working of a disc brake system where the friction is caused on the disc instead.
Components of a drum brake:
The backing plate forms the framework for the other braking components. Because of this, all functions of the braking system exert pressure on the backing plate and so the backing plate is manufactured to be strong enough
While braking, the brake pads push against the brake drum. Due to this, a lot of heat is generated and the brake drum tends to get worn over time as well as the brake pads. In order to avoid overheating and to reduce wear and tear, drum brakes are made of a special type of cast iron.
The wheel cylinder consists of a hydraulic cylinder, two pistons that operate brake shoes and a spring. When hydraulic pressure is applied in the master cylinder, it reaches the wheel cylinder through the lines and pushes the pistons outward. This presses the brake shoes against the brake drum. And when the brake is released, the spring pulls both the pistons back towards the cylinder.
Brake shoes are the components that apply physical pressure to the brake drum. The brake shoe generally consists of two parts, the web and the lining. The web has the necessary slots for the hold-down hardware, parking components and self-adjustment parts. It also forms a framework for the lining. Since the linings push hard against the rotating wheel, the linings should be made of materials that withstand it. A single braking system has two brake shoes. The primary is placed towards the front of the vehicle and the secondary on the other side. According to the braking motion, the primary shoe is positioned slightly different from the secondary shoe.
The drum brake does two functions. They are, normal braking, and emergency braking. In the working of the normal braking, when the brake pedal is pushed, the hydraulic system gets activated, and pushes the hydraulic fluid. At the brake drum, the wheel cylinder receives the pressures and pushes the pistons on both the sides against the walls of the drum to cause friction.