TM 5-3895-346-14
CONTROLS
HYDROSTATIC SYSTEM
spring also increases spring deflection) until controlling land (E) on the spool covers the controlling port (F). The
override pressure is defined as the system pressure when land (E) covers port (F).
As the system pressure increases above the override pressure, the spool and land (E) shift further toward the
spring and the port (F) is opened to the tank, thus draining the pressurized servo cylinder and allowing
displacement of the variable pump to decrease.
The pressure override will modulate so that a servo pressure is maintained, to maintain a displacement which
will yield a system pressure equal to the override pressure.
The override pressure is adjustable by turning the screw (H) and varying the preload on the spring. The
override pressure will vary approximately 1000 psi per full turn of the screw (H).
ROTARY BYPASS OPERATION
The rotary bypass valve is used in conjunction with a Sundstrand manifold valve assembly which is normally
associated with a Sundstrand Variable or Fixed Motor. The rotary bypass valve cross ports flow across the
motor (load).
The rotary bypass valve assembly is a two-way valve (refer to Fig. 4). In the closed position, the valve is
blocked and has no function to the system. In the open position, the valve ports fluid from side (A) of the
closed loop to side (B) or vice versa.
The rotary bypass valve is to be used only in the full-open or full-closed position. The valve should not be used
to control the speed of the motor as undesirable heat will be generated.
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