DRIVE SYSTEMS
Mechanical steering systems may be driven by
either a rotary or linear drive unit. Some steering
systems are fitted with an autopilot drive shaft,
and in such cases the choice of a rotary drive
system is straightforward. In general, if a drive
shaft exists and lost motion does not exceed 2 %
of total rudder movement, the rotary drive unit
becomes the most economic choice. In all other
cases the linear drive unit will provide the simplest
installation since it may be connected directly to a
tiller link on the rudder stock. Total independence
of the mechanical steering linkage also allows the
linear drive unit to be used to power steer the
vessel in the event of steering linkage failure, and
this is an important safety feature. In addition,
minimisation of working parts improves the overall
efficiency of the rudder drive system and reduces
lost motion to an absolute minimum.
All vessels with hydraulicsteering systems will
require a hydraulic drive unit.
1.2.1 ROTARY DRIVE UNIT
The output shaft is driven by a continuously rated
servo motor via an efficient reduction gearbox.
The gearbox is dry lubricated to permit operation
in any attitude. A fail safe friction clutch within the
gear train engages automatically when the
autopilot is switched to ‘Auto’ and will disengage
instantly even under extreme load when the
autopilot is switched to ‘Stand-by’. The motor is
controlled by the course computer which also
regulates peak armature current and eliminates
the need for end limit switches.
Supply voltage
Peak output torque
Maximum shaft speed
Power consumption (typical
average)
Overall depth ‘A’
Suilable for vessels up to
12 volts (24 volts optional)
12 volts (24 volts optional)
(27Nm)
(48Nm)
18 rpm
28 rpm
1
amps
4-7 amps
8.1 in. (21 Omm)
45ft.
60ft.
(18m)
2 HOLES:
(0.5”) diameter
