When a brake pedal is pressed and the S-cam is turned, the S-cam:
Answers
Presses the brake shoes against the inside of the brake drum.
Tightens the brake drum onto the axle.
Presses the brake lining against the wheel.
Releases air from the air tanks.
The Correct Answer and Explanation is :
The correct answer is: Presses the brake shoes against the inside of the brake drum.
Explanation:
The S-cam is a crucial component of drum brake systems, particularly in air brake systems, commonly used in large vehicles such as trucks and buses. Here’s how it functions:
- Pressing the brake shoes: When the brake pedal is pressed, air is sent to the brake chambers, which are connected to the S-cam. The air pressure pushes a diaphragm inside the brake chamber, which in turn moves a rod that is connected to the S-cam. The S-cam is a camshaft shaped like the letter “S,” and as it rotates, it pushes the brake shoes outward.
- Brake shoe contact with the drum: The brake shoes, which are lined with friction material, move outward against the inside of the brake drum due to the rotation of the S-cam. This contact creates friction, which slows down and eventually stops the rotation of the wheel, thus applying the brake.
- Not tightening the drum onto the axle: The S-cam does not serve to tighten the drum to the axle. The brake drum is mounted on the axle, and the S-cam’s role is to apply friction, not to alter the mechanical connection between the drum and the axle.
- Not pressing the brake lining against the wheel: The brake lining is part of the brake shoes, and it presses against the inside surface of the brake drum, not directly onto the wheel.
- Not releasing air: The purpose of the air system in an air-brake setup is to apply pressure to the brake chambers, not to release air from the tanks during braking. The release of air occurs when the brake pedal is released, disengaging the brakes.
In summary, the primary function of the S-cam in a drum brake system is to rotate and press the brake shoes against the inside of the brake drum, creating the necessary friction to stop the vehicle.