Service Manual

Greensmaster 3250--D
Hydraulic System (Rev. I)
Page 4 -- 25
Right and Left Turn
The gear pump (P2) is directly coupled to the hydrostat
through gear pump (P1). It supplies hydraulic pressure
to the steering control valve for turning the rear wheel,
for raising and lowering the cutting units, and for main-
taining 100 to 150 PSI (6.9 to 10.3 Bar) to the low pres-
sure side of the traction circuit (charge pressure). The
gear pump (P2) takes its suction from the hydraulic res-
ervoir. Maximum circuit pressure is limited by relief valve
(R5).
With the steering wheel in the neutral position (rear
wheel positioned straight ahead) and the engine run-
ning, the s pool valve is in the center position. Flow en-
ters the steering control valve at Port (P) and goes
through the spool valve, by--passing the steering cylin-
der. Flow leaves the control valve out port (PB) and con-
tinues through solenoid valve (S2) to the hydrostat.
Right Turn
When a right turn is made with the engine running, the
turning of the steering wheel positions the spool valve so
that flow goes through the top of the spool. Flow entering
the steering control valve at Port (P) goes through the
spool and is routed to two places. First, most of the flow
through the valve is by--passed out port (PB) back
through solenoid valve (S2) to the hydrostat. Second,
the remainder of the flow is drawn through rotary meter
(V1) and out port (R). Pressure moves the piston in the
direction for a right turn. The rotary meter ensures that
the oil flow to the cylinder is proportional to the amount
of the turning on the steering wheel. Fluid leaving the
cylinder flows back through the spool valve then out port
(T) and to the hydrostat.
The steering wheel and steering control valve return to
the neutral position when turning is complete.
Left Turn
When a left turn is made with the engine running, the
turning of the steering wheel positions the spool valve so
that flow goes through the bottom of the spool. Flow en-
tering the steering control valve at Port (P) goes through
the spool and is routed to two places. First, most of the
flow through the valve is by--passed out port (PB) back
through solenoid valve (S2) to the hydrostat. Second,
the remainder of the flow is drawn through rotary meter
(V1) and out port ( L). Pressure moves the piston in the
direction for a left turn. The rotary meter ensures that the
oil flow to the cylinder is proportional to the amount of the
turning on the steering wheel. Fluid leaving the cylinder
flows back through the spool valve then out port (T) and
to the hydrostat.
The steering wheel and steering control valve return to
the neutral position when turning is complete.
Hydraulic
System