Furuno NAVPILOT 700, NAVPILOT 720 Instruction Manual
HYDRAULIC LINEAR ACTUATOR
LA11
TABLE OF CONTENTS
1. GENERAL INFORMATION ............................................... p. 01
2. TECHNICAL SPECIFICATIONS and APPLICATION ........ p. 02
3. DESCRIPTION ................................................................. p. 03
3.1 General
3.2 Pump Unit (HRP11)
3.3 Reservoir/Bypass Assembly
3.4 Steering Cylinder
4. INSTALLATION ................................................................. p. 05
4.1 Mechanical
4.2 Hydraulic
4.3 Electrical
5. NOTES ............................................................................. p. 07
6. DRAWINGS ..................................................................... p. 08
6.1 LA11 — Assembly Schematic
6.2 LA11 — System Connection Schematic
i
1. GENERAL INFORMATION
The Accu-Steer LA11 unit is a hydraulic linear actuator designed
to interface an autopilot system with a mechanical steering systems such as wire, cable or chain drives. A hydraulic linear actuator consists of a hydraulic drive unit (containing a pump unit,
bypass valve and reservoir assembly), a steering cylinder and the
interconnecting hoses.
One end of the cylinder is xed and the other end is connected to
a tiller arm or the mechanical quadrant, which is connected to a
rudder shaft. With this connection to a tiller arm the linear movement of the cylinder is changed to rotary movement, which turns
the rudder and steers the vessel.
During normal mechanical steering, the hydraulic steering cylinder
strokes to port and starboard as the vessel is steered manually.
The oil in both sides of the cylinder ows back and forth through
a normally open bypass valve located in the linear actuator drive
unit. The steering cylinder is connected to the drive assembly with
two hoses (port and starboard). When the autopilot is switched into
the operating mode, the bypass valve is electrically closed. The
autopilot then drives the reversing hydraulic pump which in turn
operates the steering cylinder. See section 3 of this manual for a
more in depth description.
When the autopilot is operating, the cylinder with be turning the
rudder. The mechanical steering will be back-driven during this
time. The vessel’s steering wheel will be turning as the autopilot
makes corrections.
The Accu-Steer HRP11 is the reversing pump unit used in the LA11
linear actuator. The output ow rate of the pumpset determines the
speed of the steering cylinder. The HRP11 pump outputs 1.0 cu
in/sec or 16.4 cc/sec.
The BA150 X 9 is a balanced steering cylinder, which means the
volume of oil on both sides of the cylinder is equal. The volume of
this steering cylinder is 13 cu in (215 cc) of oil.
p01
2. TECHNICAL SPECIFICATIONS and APPLICATION
Model Number LA11-12 LA11-24
Voltage 12 VDC 24 VDC
Output/Sec 1 cu in/sec 1.0 cu in/sec
Average Motor Amp 3-6 2-4
Solenoid Valve Amp 1.5 AMPS .75 AMP
Weight 15 lbs (7 kgs) 15 lbs (7 kgs)
The output of the hydraulic reversing pump is 1.0 cu in/sec. The
volume of the steering cylinder is approximately 13.1 cu in (215 cubic centimeters). The rudder speed will be approximately 13 seconds hard over to hard over (HOH).
The rudder speed, hard over to hard over (HOH), is determined
by dividing the volume (cu in) of the cylinder by the output of the
pumpset (cu in/sec).
The steering cylinder is capable of approximately 785 lbs of thrust
based on an output of 500 psi from the pump. The force or torque
applied to the rudder through the rudder shaft is dependent of the
distance between the center of the rudder shaft and the position
of the tiller bolt.
Figure 2 CYLINDER SCHEMATIC
35°
PORT
45°
PORT
7.875"
TILLER ARM
RUDDER SHAFT
6.0"
35°
PORT
45°
PORT
4.5625"
23.25"
35° TRUNNION CENTER
45° TRUNNION CENTER
6.75"
Distance (rudder shaft to tiller bolt): 6” = 4,710 in/lb; 7” = 5,495 in/lb;
8” = 6,280 in/lb; 9” = 7,065 in/lb. The torque required to turn the rudder
can be calculated or obtained from the vessel’s builder.
p02
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