SUBSECTION 5A
HYDRAULIC SYSTEM
through the control, through a shuttle valve, to the third
The load may be lowered by gravity or powered down. To
drum brake cylinder. Oil flowing into the brake cylinder will
lower a load by gravity, the operator slowly releases the
cause the cylinder piston to extend, releasing the third drum
brake pedal. This allows oil to flow out of the brakecylinder,
brake and allowing gravity to lower the load.
through the drum brake valve, to the reservoir. Oil flowing
out of the brake cylinder will cause the cylinder piston to re-
tract, allowing springs to release the drum brake and lower
PROPEL BRAKE CIRCUIT. The propel brake circuit consists
the load.
of the propel brake switch and valve. To release the propel
brake, the operator moves the switch to the OFF position. In
To power down a load, the operator moves the drum con-
this position hydraulic oil passes from the accumulator,
trol forward and slowly releases the drum brake pedal. In
through the brake valve, through the swivel, and to the
these positions hydraulic oil passes from the accumulator,
propel brakes. Oil flowing into the brake chambers forces
through the planetary brake valve, to the planetary brake
the piston against the brake springs, releasing the pres-
cylinder. Releasing the brake pedal allows oil to flow out of
sure on the brake disc plates, allowing the brake discs to ro-
the brake cylinder, through the brake valve, to the reser-
tate.
voir. Oil flowing into the planetary brake cylinder causes the
cylinder piston to extend applying the planetary brake to
To apply the propel brake the operator moves the switch to
power down a load. Oil flowing out of the brake cylinder will
the ON position. In this position hydraulicoilflowsoutof the
cause the cylinder to retract, allowing springs to release the
brake chambers and returns to the reservoir. Oil flowing out
drum brake.
of the brake chambers allows springs tocompressthebrake
discs between the brake disc plates. The brake disc plates
THIRD DRUM CIRCUIT. The third drum circuit includes the
are prevented from rotating.
third drum brake and clutch control. To lift a load, the opera-
tor pulls the lever back. In this position, hydraulic oil passes
from the accumulator, through the control valve, to the third
CRAWLER EXTENSION AND RETRACTION CIRCUIT. This
drum clutch. Oil also passes through a shuttle valve to the
circuit includes the two quick connect hoses on the under-
third drum brake. Oil flowing into the third drum brake
side of the revolving frame and one control on the left front
cylinder will cause the cylinder piston to extend and release
side of the upper. To extend the crawler tracks the operator
the drum brake. Oil flowing into the third drum clutch
moves the control to the "extend" position. In this position
cylinder will cause the cylinder piston to extend applying
hydraulic oil from the pump is directed to the blind end of
the clutch and lifting the load.
the extension cylinders causing the piston rods to extend.
Hydraulic fluid from the head end of the cylinders is di-
To stop drum rotation, move the third drum control to neu-
rected back to the reservoir.
tral. In this position, hydraulic oil will flow out of the third
drum clutch and brake cylinders to the reservoir. Oil flow-
ing out of the clutch cylinder will cause the cylinder piston
To retract the crawler tracks the operator moves the con-
to retract and allow springs to release the drum clutch. The
trol to the "retract" position. In this position hydraulic oil
third drum brake will spring set when oil flows out of the
from the pump is directed to the head end of the extension
brake cylinder.
cylinder causing the piston rods to retract. Hydraulic fluid
To lower a load, the operator pushes the lever forward. In
from the blind end of the cylinders is directed back to the
this position hydraulic oil passes from the accumulator,
reservoir.
5A-10
