Operation Manual

1. GENERAL INFORMATION
A hydraulic steering system consists of a hydraulic actuator (normally a
cylinder) and one or more steering wheel pumps (helm pumps). As the
steering wheel (helm pump) is turned in the port direction, hydraulic oil is
pumped into the port hydraulic steering line. This oil is directed into the
port side of the steering cylinder. As the cylinder moves to port, oil from
the starboard side of the cylinder returns to the helm pump through the
starboard hydraulic lines.
One end of the cylinder is xed and the other end is connected to a tiller
arm, which is connected to a rudder shaft. With this connection to a til-
ler arm the linear movement of the cylinder to port is changed to rotary
movement, which turns the rudder and steers the vessel to port.
Moving the steering wheel to starboard produces the same re-action with
oil being pumped out of the starboard line and returning through the port
line. If more the one helm pump is used, a return/ll line must be installed
to connect the cases of all the helm pumps together.
If an autopilot is to be installed, the hydraulic reversing pumpset is con-
nected in the same manner as a helm pump with a port, starboard and a
return/ll line.
The Accu-Steer HRP05, HRP11 and HRP17 are reversing pump units
designed to interface a hydraulic steering system with electric or autopilot
control. The output ow rate of the pumpset determines the speed of the
steering cylinder. The HRP05 pumpset outputs 0.5 cu in/sec or 8.2 cubic
centimeters per second. The HRP11 pumpset outputs 1.0 cu in/sec or
16.4 cc’s/sec. The HRP17 outputs 1.6 cu in/sec or 26.3 cc’s/sec.
Most steering cylinders are balanced, which means the volume of oil
on both sides of the cylinder is equal. A steering cylinder is balanced
when the piston rod of the cylinder protrudes from both ends. Some cyl-
inders are unbalanced in which the piston rod protrudes from one end
only. These are common on some in-board and out-board drives and are
usually referred to as side drives or simply unbalanced cylinders. These
Accu-Steer HRP pumpsets are capable of working with both balanced
and unbalanced cylinders. When unbalanced cylinders are used it is rec-
ommended that a vented header tank is used to allow for the expansion
and contraction from the unbalanced cylinder.
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