Page 242 - Introduction to Marine Engineering

220 Steering gear

4,.

Tiller
Cylinder
Crosshead

Pump J h~T
'U
Motor Motor

Replenishing
tank

Figure 12.6(a) Diagrammatic arrangement of two-ram steering gear (additional items for
four-ram system shown dotted)

linkage on the tiller will prevent damage to the control gear during a
shock movement.
During normal operation one pump will be running. If a faster
response is required, for instance in confined waters, both pumps may
be in use. The pumps will be in the no-delivery state until a rudder
movement is required by a signal from the bridge telemotor transmitter.
The telemotor receiver cylinder will then move: this will result in a
movement of the floating lever which will move the floating ring or
slipper pad of the pump, causing a pumping action. Fluid will be drawn
from one cylinder and pumped to the other, thus turning the tiller and
the rudder. A return linkage or hunting gear mounted on the tiller will
reposition the floating lever so that no pumping occurs when the
required rudder angle is reached.
A four-ram steering gear is shown in Figure 12.7. The bask principles
of operation are similar to the two-ram gear except that the pump will
draw from two diagonally opposite cylinders and discharge to the other
two. The four-ram arrangement provides greater torque and the