The modern-day drum brake system dates back to the 1900s when it was initially integrated by a German car manufacturer in its vehicles. Its improved version was later patented by another European OEM two years later. Drum brakes on wheels were initially manufactured from asbestos (a naturally long and thin fibre that is resistant to heat, electricity, and chemicals).
Drum brakes initially deployed cable rods and levers which worked in sync to operate the brake shoe mechanically. A few decades later i.e. in the 1930s, a wheel cylinder and a piston were deployed to control the oil pressure.
Components of Drum Brakes
There are various parts in the drum braking system that work in sync to make braking effective. These include: -
Brake Shoe
Brake shoe pads are one of the key components in the drum braking system. They are two pieces of steel welded together to create friction. Each brake assembly on a wheel has two shoes, one primary and the other secondary. Their shape resembles a semi-circle and they don’t have any direct contact with the brake drum.
Backing Plate
It is a metal-based band, thin in size, which protects other components of the drum brake. It has a round shape with multiple holes, the purpose of which is to match the drum brake’s standard part.
Wheel Cylinder
It is a small yet very crucial component of the drum braking system. It is used for converting fluid pressure into mechanical pressure that engages the brake shoe. A wheel cylinder consists of various parts: - bleeder nut, piston boot, piston, and the wheel cylinder housing. Its efficiency is directly linked to the braking response.
Return Spring
This is also a very crucial part of the drum brakes. Its main function is to return the brake shoe back to its original position before the brake lever. There are two springs in a drum brake – the upper spring and the lower spring.
The upper spring is located under the cylinder wheel and retracts the brake shoe back to its original place. The lower spring, on the other hand, maintains the position of the two drum brake shoes so that they press on the adjuster.
How do Drum Brakes Work?
When the rider presses the brake lever, the power gets amplified by a brake booster and is changed into mechanical pressure by a master cylinder. The pressure then gets transferred on the wheels via a plumbing of tubes filled with brake oil.
Once the brake oil reaches the ideal pressure, it pushes the piston and creates friction on the surface of the brake drum which is rotating in sync with the vehicle’s speed. The constant friction causes the vehicle to decelerate, thereby slowing down/ stopping the vehicle. The two shoes function in a way that they both become a leading or a trailing show. The drum brake generates the same braking force in either direction depending on whether a vehicle is moving forward or backwards.
Drum brakes are also fitted with parking brakes. Furthermore, due to the fact that the braking contact area is at the circumference of the brake, a drum brake can provide more braking force than its counterpart, and it also allows the drum brake to last longer. Drum brakes may retain heat and are more complex, but when it comes to rear brake application, they remain the more economically viable and powerful brake type, especially in vehicles like those from
TVS Motor.
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