FUNCTION OF THE TRANSMISSION MOUNTED HYDRAULIC BRAKE
The transmission mounted hydraulic brake is designed for the most part to be used on rough terrain vehicles. The
hydraulic brake mounted on the transmission is used as the main braking source in log skidder applications where wheel
brakes are not practical.
The transmission mounted hydraulic brake consists of an internally splined housing bolted to an adaptor plate that is
bolted directly to the transmission case. A brake disc hub is splined to the idler shaft and also has splines on the outer
diameter. This hub is free to turn until brake pressure is applied.
Steel discs with splines on the outer diameter are alternated with frictional discs having splines on the inner diameter.
The steel disc splined in the brake housing cannot turn, but are free to move in or out. The frictional discs splined to the
hub on the idler shaft may turn in either direction or may increase or decrease in speed depending on the operator's
discretion. The frictional discs are also free to move in or out.
The brake system has a positive displacement of fluid from the master cylinder to the three brake actuating pistons.
The cooling of the clutch disc brake is accomplished by return oil from the cooler plumbed to the brake disc compartment
with a tee fitting.
When the brake Is applied, pressure behind the pistons forces a heavy end plate to overcome the return spring pressure.
The steel discs (splined In the stationary housing) are compressed against the friction discs (splined on and turning with
the Idler shaft). As more brake pressure Is applied the discs are compressed tighter until the Idler shaft is stopped. The
output shaft which Is geared directly to the Idler shaft Is also stopped. As the brake Is engaged, brake pressure
overcomes a spring loaded brake valve spool and moves the brake spool open allowing a 70% volume of return oil to
cool the brake discs. The volume of return oil remaining Is directed to the lube distributor and Is sufficient to cool and
lube the transmission.
When the brake is released, return springs push the end plate and pistons to a neutral position allowing the inner and
outer discs to separate. The friction disc and idler shaft is now free to turn.
When the brake is disengaged the spring loaded brake valve spool is closed allowing a 20% volume of return oil to cool
the brake disc, the remaining oil is directed to the lube distributor.
The transmission mounted hydraulic brake can also be used as a parking brake. It is actuated by a hand brake lever and
linkage to a shaft on the side of the brake housing. The shaft is connected internally to a yoke. When the hand brake
lever is set, the yoke presses against the heavy end plate and compresses the inner and outer clutch brake discs, thus
making the idler shaft immobile.
When the hand brake lever is released the yoke moves away from the end plate allowing the return springs to move the
end plate away from the discs. The friction disc and idler shaft is now free to turn.