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How to purge a Linear
Drive after installation
1. Verify that there is no air in the
ram:
Disconnect the pump motor from the Drive-
box, but keep the Bypass Valve connected.
Engage the autopilot now: the valve will
close and lock the rudder. Try to move your
helm or tiller with moderate force to Star-
board, then reverse your force to Port. The
piston rod should not move more than 1 mm
(1/32 in.) if air has been purged completely.
Otherwise you have to purge the air from the
cylinder.
2. Purging the last bit of air:
Important: keep the purge valves closed (at
the ram and the pump), do not use them.
Disconnect the rudder sensor mechanically
from the rudder, so it will not move, when the
rudder moves.
Further, we must be able to work the piston
to the very end of the cylinder, both sides.
This will normally necessitate detaching the
piston rod from the tiller arm or quadrant. Or
else we might hit a mechanical rudder stop,
before the cylinder reaches its limit.
Rotate the sensor shaft so as to get a cen-
ter position on the LED of the autopilot display.
With the motor and the valve reconnected
to the Drivebox, engage the autopilot in Head-
ing Mode (make sure the heading does not
change and the boat is moored firmly).
Turn the sensor shaft about three degrees
to either side, this will start the pump. Don't
turn the sensor too far or the autopilot will
disengage. Stay there until the piston hits the
cylinder end firmly. Then turn the sensor shaft
quickly back to reverse the pump, and stay
there, until the piston hits the other end of the
ram. Repeat that 10 times with full rudder
speed.
3. Verify again according step 1
above!
Hydraulic Steering
Pump Installation
The electric pump is normally mounted
near the steering cylinder. Three hydraulic
hoses are required, to connect it to the steer-
ing system. The wheel pump must have check
valves installed or the Steering Wheel will
start turning, when pressure builds up from
the electric pump. Some wheel pumps don't
have check valves; they require installation of
a check valve block next to the wheel pump.
Boats with two hydraulic steering wheels
have check valves already installed.
After making the required hydraulic con-
nections, the system needs to be filled with oil.
Automatic transmission fluid for automobiles
has to be used. Purge air according instruc-
tions for the steering system. Eventually re-
peat purging after brief operation of the auto-
pilot or Servo Steering. Some autopilot pump
models allow purging at the pump itself. In
case of pressurised hydraulic systems, do not
exceed the prescribed air pressure.
Adjustment of pump flow
Some pumps permit to adjust mechanically
their flow, to vary the maximum available rud-
der speed. Always select the maximum
pump flow.
Maximum Rudder Speed Selection
A high maximum rudder speed is desirable
for good autopilot function. However it is a
must for Servo Steering. A low maximum rud-
der speed can lead to heading oscilla-
tions. Danger! Therefore the maxi-
mum available rudder speed should
always be selected. The Tecnautic Drive-Box
is regulating the pump speed electronically
and reducing rudder speed automatically,
whenever necessary.
WARNING:
If the autopilot does not keep the selected
heading (in HDG mode), the first thing to
check is the stiffness of the hydraulic system.
Switch off the autopilot and the electronic
servo steering. Then apply physical force onto
the rudder with the emrgency tiller. Do NOT(!)
use the hydraulic helm. The piston should not
move more than 1 mm (1/32") at maximum.
46
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