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| Illustration 1 | g00551583 |
Wheel brakes (rear drum) (1) Brake support (2) Brake drum (3) Piston (4) Wheel cylinder (5) Wear adjusters (6) Hex head screws (7) Spring (8) Primary brake shoe (9) Secondary brake shoe (10) Pivot point for brake shoes | |
The brake system is activated by pushing downward on the wheel brake pedal or by operating the oscillating axle control and operating brake control on the left console.
When the brake pedal is depressed, hydraulic oil flows from the master cylinder to each wheel cylinder (4). The hydraulic oil pressure forces the two pistons (3) inside the wheel cylinder (4) outward. This forces brake shoes (8) and (9) to pivot outward in order to extend spring (7). Braking action is the result of friction between the two brake shoes (8) and (9), and the brake drum (2) .
When the brake pedal is released, the spring (7) returns brake shoes (8) and (9) away from the brake drum (2). This disengages the brakes. Pistons (3) inside each wheel cylinder (4) are forced inward. This forces hydraulic oil in each wheel cylinder (4) to flow back to the brake master cylinder.
Wear adjusters (5) hold the given clearance constant over the life of the shoe linings. Hex head screws (6) of wear adjusters (5) must remain in the adjusted position. To change the contact pressure between brake shoes (7) and (8), hex head screws (6) must be turned to the left or to the right until the brake drum rotates freely.