PUMP NEUTRAL ADJUSTMENT (continued from
If the transmission operates as shown by motor
shaft rotation, reduce speed to idle. Using a
3/16inch internal hex wrench, slowly turn the
does not operate. Repeat step 6. Note that
charge pressure should drop approximately 20
psi with forward or reverse stroking of the pump
swashplate due to the shifting of the shuttle
valve in the motor manifold.
With a 3/16-inch internal the wrench, slowly turn
the null adjustment screw clockwise
charge pressure begins to decrease. Then
, observing the angle of
rotation, until charge pressure decreases again
(charge pressure will rise in neutral and drop
when going into stroke).
A range of options to the basic HDC allows it to be
custom-tailored to each application. The control is
specified by filling in each slot of the order number, as is
shown in Table B, with the appropriate model code.
Other options are possible. Consult Sundstrand Mobile
Controls with further questions.
TABLE B. INFORMATION NECESSARY TO SPECIFY
THE HYDRAULIC DISPLACEMENT CONTROL.
This is the basic HDC. The model code is
CONFIGURATION (including assembly kit)
*PRESSURE OVERRIDE ONLY
**MODEL CODE 7 DEVICES MAY NOT BE USED ON
SERIES 3X PUMPS IF ORDERED LESS LINKAGE
ASSEMBLY ("9 UNDER THE SERIES PARAMETER).
Turn the adjustment screw clockwise
the amount of the turn observed in step 8. This
should be the center of neutral.
Hold the adjustment screw and securely tighten
the hex lock nut on the adjustment screw to 14-
18 foot-pounds. Note that if a motor is used
which does not have a manifold, neutral should
be adjusted (steps 810) by observing the motor
output shaft rotation without a load.
Stop the prime mover.
Run the system briefly to ensure that it
operates proportionally on both sides of
movement can be verified by watching
movement of the swashplate feedback
shaft, shown in Figure 1. The Pressure
Override and Pressure Limiter accomplish
the same function-they shift the pump
swashplate toward neutral when system
pressure crosses a pre-set threshold.
They thus limit system pressure, protect
components from heat generated by flow
across relief valves and conserve pump
Pressure override is available only for Series 2X pumps,
and pressure limiting is available only for Series 3X
pumps. Pressure limiting and annular control are not
available together. If the model code chosen indicates
that the pressure override/pressure limiting function is
desired (i.e., "yes" is chosen in the second column of the
configuration parameter, above), only pressure limiting
will be provided directly by Sundstrand Mobile Controls
(pressure limiting is accomplished using a different
porting spool); the Pressure Override Valve must be
obtained through Sundstrand Hydrotransmission. See
Stroke controls with annular control have a groove cut
into the spool bore of the housing that allows for higher
flow from the control ports when they are uncovered,
increasing swashplate response.
Kits are needed in order to install the HDC onto the
pump. Which kit is shipped with the HDC depends on
which pump series is ordered. Included in the kit are:
retaining rings, swashplate pin, drag link, orifice, hex
screws, O-rings and gasket. In some cases not all of the
above are necessary for installation, and they are not
included with the kit. Individual drag links will not be
supplied by Sundstrand. Consult Mobile Controls for
ORDERING INFORMATION (continued page 8)
Sundstrand Mobile Controls