List all the parts of a typical drum brake.
The correct answer and explanation is :
A typical drum brake system consists of several key parts that work together to slow down or stop a vehicle. These parts include:
- Brake Drum: The large, cylindrical component that rotates with the wheel. It provides the surface against which the brake shoes press to create friction.
- Brake Shoes: These are curved metal components lined with friction material, typically made of a composite of metals, resins, and other materials. They press against the inside of the brake drum to slow the vehicle down.
- Wheel Cylinder: A hydraulic component located at each end of the brake shoes. It contains pistons that push the brake shoes outward against the drum when hydraulic pressure is applied.
- Brake Shoe Return Springs: These springs return the brake shoes to their original position when the brake pedal is released.
- Adjuster Mechanism: A system that automatically compensates for brake shoe wear. It ensures that the shoes maintain the correct distance from the drum for efficient braking.
- Parking Brake Lever: A lever connected to the parking brake mechanism, which allows the driver to lock the brake shoes in place for parking.
- Primary and Secondary Brake Shoes: The primary brake shoe is the one that faces the front of the vehicle and is most actively engaged when the brake is applied. The secondary brake shoe is usually behind the primary and acts as a backup.
- Backing Plate: A metal plate that provides a sturdy mount for all of the brake components, including the shoes, wheel cylinder, and return springs.
- Hydraulic Lines: These lines carry brake fluid from the master cylinder to the wheel cylinders, enabling the hydraulic pressure needed to activate the brakes.
Explanation:
Drum brakes operate based on friction. When the driver presses the brake pedal, hydraulic pressure from the master cylinder is sent through the brake lines to the wheel cylinder, causing the pistons to push the brake shoes against the inside of the rotating brake drum. The friction between the shoes and the drum generates heat and slows the vehicle down.
The design of drum brakes allows for a relatively simple, reliable braking system, though they tend to generate more heat compared to disc brakes. The heat can cause brake fade, reducing braking efficiency, especially in high-performance situations. However, drum brakes are still commonly used in older or less performance-demanding vehicles due to their cost-effectiveness and reliability.