INTRODUCTION 16000 SERVICE/MAINTENANCE MANUAL
1-28
Published 05-09-17, Control # 014-28
Travel motors are variable displacement and shift internally
with an adjustable spring in each motor P/C (Pressure/
Compensator) valve, preset at approximately 3,915 psi (270
bar). Travel motors are in minimum displacement (low
torque, high-speed) position when starting. When crawler
begins to move, a high system pressure shifts the PCOR
(Pressure Compensated Over-Ride) spool placing travel
motor in maximum displacement (high torque, low speed)
position for breakaway torque.
As travel control handle is moved to neutral position, Node-1
controller compensates for hydraulic system leakage or
changing engine speed. Node-3 controller sends a zero
output voltage to pump EDC to move swashplate to center
position. After travel control handle command is off for a
preset time, the Node-5 controller sends a zero output
voltage to disable travel brake solenoid HS-5. Travel brake
valve shifts to block pilot pressure to brakes and opens a line
to tank. Brakes apply.
Two-Speed Travel Operation
Travel two-speed switch allows operator to select low speed
when smoother starts and precise control over the load is
required. Low speed places travel motor in maximum
displacement (high torque, low speed) position and prevents
motor from shifting to high speed. When travel two-speed
switch is in low speed position, Node-5 controller sends a 24
volt output to enable two-speed travel solenoid HS-6, shifting
valve and directing hydraulic pilot pressure to P/C (Pressure/
Compensated) valve. The P/C valve shifts PCOR (Pressure
Compensated Over-Ride) spool placing travel motor in
maximum displacement (high torque, low speed) position.
Travel motors remain in this position until travel speed switch
is placed in high speed position and engine speed is more
than 1500 RPM.
Place travel two-speed switch in high speed when maximum
available travel speed is required (normal operation).
Hydraulic pressure required for releasing travel two-speed
solenoid valve is from accessory/MAX-ER pump at 400 to
500 psi (28 to 35 bar). When travel two-speed switch is in
high speed position, travel motors shift to minimum
displacement (low torque, high speed) automatically if
engine speed is above 1500 rpm and system pressure is
below 3,915 psi (270 bar). If engine is below 1500 RPM, two-
speed travel solenoid HS-6 is enabled although travel two-
speed switch in the high position. Travel two-speed solenoid
HS-6 is disabled, shifting valve and removing hydraulic pilot
pressure to P/C valve, allowing motor to operate in PCOR
mode.
Travel Cruise
When the travel cruise switch is moved to cruise position, an
input signal is sent to Node-1 one controller. Node-3
controller sends an output signal to travel pumps to lock-in
selected flow requirements and direction.
Moving the travel cruise switch to off position or moving
either travel handle in opposite direction from neutral sends
an input signal to Node-1 one controller. Node-3 controller
sends an output signal to travel pumps to open travel cruise
circuit and return control of travel system to the operator.
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