What is pushed out of the brake chamber to apply the foundation brake?
- A pushrod ✓
- A diaphragm
- A clevis
- Compressed air
Answer: A. A pushrod
A pushrod is pushed out of the brake chamber to apply the foundation brake.
Why this is the answer
The handbook says compressed air fills the service brake chamber and moves the diaphragm, which pushes out the pushrod to apply the brakes. When air pressure is released, the spring returns the pushrod. Another passage adds that pushrod stroke acts on the slack adjuster and camshaft, which forces the brake shoes against the drum. So the part that moves outward from the chamber to start the foundation brake action is the pushrod.
Why the other answers are wrong
- B. A diaphragm — The diaphragm is the flexible disc inside the chamber that moves when air enters; it is not the rod pushed out.
- C. A clevis — The passages do not describe a clevis as the part pushed out; they identify the pushrod as the rod that leaves the chamber.
- D. Compressed air — Compressed air is what enters the chamber to create movement, not the part pushed out to apply the foundation brake.
Remember it
Picture air entering and pushing the diaphragm, which then pushes the rod outward: air in, pushrod out.