What is the S-cam used for?

What is the S-cam used for?

• A. To release the brakes
• B. To adjust the brake shoes
• C. To cool the brakes
• D. To put on the brakes

Answer: (D)

In air brake systems, the S-cam is the mechanism that actually applies the brakes. When air pressure fills the brake chamber, the piston pushes the push rod, which rotates the S-shaped cam. As the cam turns, its lobes spread the brake shoes outward so they press against the brake drum, creating friction to slow or stop the wheel. Releasing pressure lets springs pull the shoes back away from the drum, releasing the brake. So the S-cam’s job is to put on the brakes, not to release or adjust them.

In air brake systems, the S-cam is the mechanism that actually applies the brakes. When air pressure fills the brake chamber, the piston pushes the push rod, which rotates the S-shaped cam. As the cam turns, its lobes spread the brake shoes outward so they press against the brake drum, creating friction to slow or stop the wheel. Releasing pressure lets springs pull the shoes back away from the drum, releasing the brake. So the S-cam’s job is to put on the brakes, not to release or adjust them.