SkyTrak 6036 Service Manual - Manual (Page 124)

Section 9. Hydraulic System
9-11 Model 6036 S/N 9B0499 and Before
5. Starting at the full tilt up position, tilt the grille
down fully at full engine speed. The time
required for full tilt down should be 3 to 5
seconds (no load).
6. Repeat steps 4 and 5 to recheck performance.
7. If the grille tilt circuit test does not meet
performance requirements, locate the cause of
the problem and correct before putting the
vehicle into service
9.1.4 Frame Tilt Circuit
a. Description
Hydraulic pressure is applied in the frame tilt
circuit by the 30 gpm section (rear half) of the
tandem pump, which draws its fluid through a
suction screen in the reservoir, Fig. 9.5. Pressure
is directed to either side of the frame tilt cylinder
piston by the shifting of a spool in a directional
control valve found in the main control valve
assembly. The spool is shifted by the grille and
frame tilt control lever and its associated control
cable. Control lever positions for tilting the grille
are as follows:
Center Position
When the grille and frame tilt control lever is
placed in the center or neutral position, the
directional control valve spool is positioned so that
pump supply pressure is directed through ports F
to C, Fig. 9.5, to the return filter and reservoir. If
the return filter becomes clogged, hydraulic oil will
bypass the filter when the pressure reaches 10 to
15 psi (0,7 to 1,03 bar).
FRAME TILT
CYLINDER
MAIN CONTROL
VALVE
DIRECTIONAL CONTROL VALVE
POSITIONS
PILOT OPERATED
CHECK VALVE
TO GRILLE TILT AND
SLAVE CYLINDERS
STRAINER
TANDEM
PUMP
A B C A B C A B C
D E F D E F D E F
LEFT RIGHT
CENTER
FRAME TILT PORT
RELIEF VALVES
30
GPM
15
GPM
RETURN
FILTER
RESERVOIR
TO BOOM HOIST
CYLINDERS
TO BOOM EXTEND/
RETRACT CYLINDER
Fig. 9.5 Frame Tilt Circuit
RIGHT
LEFT
0-4000 psi
PRESSURE
GAUGE
MA0461