THEORY OF OPERATION - CONTINUED
BRAKE SYSTEM - CONTINUED
All four service brakes are located in axle assemblies. Service brakes are actuated by left or right brake pedal.
There are service brakes in front and rear axles.
Each service brake consists of piston, disc, plate, pins, and springs.
Plate and piston are held stationary by three pins fastened in differential housing and axle housing. Piston and plate
are able to slide on three pins. Springs keep piston retracted when not being used.
Inside diameter of disc has splines that fit on splines of sun gear. This causes disc to rotate at speed of sun gear.
Grooves are cut into faces of disc to allow passage of cooling oil even when service brakes are applied. As disc
rotates, cooling oil will constantly flow between disc and plate and between piston and disc.
Carrier is fastened to axle by splines. Axle turns with carrier. Gears in carrier rotate between sun gear and station-
ary ring gear.
When a brake pedal is pushed, pressurized oil from service brake control valve flows through oil passage in differ-
ential housing. Force of oil behind piston moves piston against force of springs.
Force of oil also pushes disc against plate. This causes friction between disc and piston and between disc and plate.
Friction causes sun gear, axle, carrier, and wheels to turn more slowly. If operator does not release brake pedal,
friction will eventually stop wheels.
Heat created from service brake friction is removed by oil in axle housings.
When brake pedal is released, oil behind piston flows through oil passage to service brake control valve. Oil then
returns to hydraulic oil tank. With no oil pressure behind piston, springs move piston to retracted position and ser-
vice brakes are released.
If machine loses power or hydraulic pump fails, service brakes can still be applied. Pressure in brake accumulators
allows several applications of brake pedals so machine can be slowed enough to engage parking brake.