Have you ever been driving down the highway and had to brake to avoid a collision with something? Then you probably pondered on how lucky you are to be alive and how grateful you are that your brakes worked. Others may have taken it upon themselves to learn exactly how their brakes operate.
In this article, we will learn about drum brakes and how they operate, but first, some fundamentals:
What is a drum brake? It is a type of brake that relies on friction generated by a set of shoes that press outward against a revolving cylinder-shaped component called a brake drum.
- Drum brakes
This component is heat-conductive and wear-resistant cast iron. When a driver applies the brakes, the lining pushes firmly on the inner surface drum, causing friction that slows or stops the wheel, causing the vehicle to come to a halt.
- Brake shoe
These are two pieces of steel that have been welded together and have the friction material riveted or attached with adhesive. The linings must be heat and wear-resistant.
- Wheel cylinder
On each end of the cylinder, there are two pistons. The wheel cylinder applies pressure to these pistons, which push the drum, slowing or stopping the vehicle.
- Backing plate
This provides a solid base for other components, increases system rigidity, supports the housing, and protects it from dust and road debris.
- Auto-brake adjuster
This component is located at the bottom of the drum brake and keeps the brake shoes and drum evenly spaced
- Return springs
A drum braking system’s return spring has upper and lower parts. When the driver lets go of the brake pedal, the brake shoes are pulled back away from the drum.
Now that you know what a drum brake is, how does it work?
How it works
- Typical breaking
When the driver presses the brake pedal, brake fluid is pumped into the wheel cylinder under pressure. As a result, the brake shoes contact the inner drum surface. When the pressure is released, return springs restore the shoes to a normal rest position, slowing the vehicle’s speed.
- Emergency brake
A set of steel cables pull on either a hand lever or a foot pedal when this is activated. This technique is entirely mechanical and bypasses the hydraulic system, stopping the vehicle even if the brakes fail altogether. The wires are connected to the brake shoes through a lever located in the brake. This effectively bypasses the wheel cylinder and controls the brakes directly.
- Automatic Self-adjustment
As the brake lining wears, they must travel a greater distance to reach the drum. A system with installed automatic adjusters automatically reacts by adjusting the rest position of the shoes so they are closer to the drum. When the brake shoes wear a bit more, the adjustment can advance again, keeping the shoes close to the drum at all times. In vehicles without automatic adjusters, you must manually adjust the brakes regularly to compensate for any excessive surplus gap between the shoes and the drum.
Drum brakes save your life every time you use them; therefore, it’s critical to have them maintained regularly. The most common service required for drum brakes is brake shoe replacement, but overall, if you don’t know where to start, talk to an industrial supplier and get your brakes sorted.