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| Illustration 1 | g00866589 |
Components of the Service Brakes (1) Spindle. (2) Friction discs. (3) Plates. (4) Piston. (5) Chamber. (6) Hub. (7) Guides. (8) Springs. (9) Axle housing. | |
The 824G Wheel Tractor is equipped with service brakes at all four wheels. The 825G Soil Compactor and the 826G Landfill Compactor are equipped with service brakes at the front wheels.
The brakes are activated by hydraulic oil pressure. The heat that is created by the friction within the brakes is removed by the oil in the axle housing.
Spindle (1) is attached to axle housing (9). The axle housing does not rotate. There are slots on the inside of the spindle. Tabs on the outside circumference of plates (3) fit in the slots. This prevents the plates from rotating. Hub (6) has splines on the outside circumference which mesh with the splines on the inside circumference of friction discs (2). The wheel assembly, which is attached to the spindle, and the friction discs rotate together.
The service brakes can be actuated by either the left brake pedal or by the right brake pedal. When the service brakes are applied, pressurized oil flows from the service brake control valve into chamber (5). The oil forces piston (4) against the stack of plates (3) and friction discs (2). This causes friction between the plates and discs. The friction causes wheel rotation to slow down. When more force is applied to the brake pedal, the pressure on the stack of plates and friction discs will increase. This causes an increase in the amount of friction in the brake which will produce more heat. The increased friction will cause the wheels to stop rotating.
Excessive heat that is created by the friction in the brakes can make the service brakes ineffective. Grooves are cut into both sides of friction discs (2). These grooves permit the circulation of oil in the brake housing between plates (3) and friction discs. The oil cools the brake components. If the groove depth on the friction discs is not adequate, the service brakes can overheat.
Reference: For more information on the requirements for the depth of the grooves on the friction discs, refer to the Service Manual module Specifications, "Service Brakes" for the machine that is being serviced.
When the brake pedal is released, oil in chamber (5) flows back through the brake control valve to the hydraulic tank. Guides (7) and springs (8) force piston (4) away from the stack of plates (3) and friction discs (2). The flow of cooling oil between the plates and the friction discs helps to separate the stack as the service brakes are released. When there is no pressure on the stack, the wheels can rotate freely.
If the machine loses power, or if the hydraulic pump fails, the service brakes can still be applied. The pressure in the nitrogen charged accumulators for the service brakes allows several applications of the brakes.