Chapter 4REDUCTION GEARS AND RELATED EQUIPMENT
The mechanical face seal is a ring made of
either a hard synthetic or a carbon compound.
This ring is held tightly against the seal ring by
springs mounted behind it.
NOTE: More information on face-type seals
is available in manufactures technical manuals
(Crane Co., Surface Ship, Seal Inc.,
The strut bearings, like the stern tube bear-
ings, are equipped with composition bushings
which are split longitudinally into two halves. The
outer surface of the bushing is machined with
steps to bear on matching landings in the bore of
Since it is usually impracticable to use oil or
grease as a lubricant for underwater bearings,
some other material must be employed for that
purpose. Materials that become slippery when wet
include natural or synthetic rubber; lignum vitae,
a hard tropical wood with excellent wearing
and laminated phenolic material
consisting of layers of cotton fabric impregnated
and bonded with phenolic resin. Strips of this
material, as shown in view C of figure 4-5, are
fitted inside the bearing. A rubber composition
is the type most used in modern installations.
CONTROLLABLE PITCH PROPELLERS
This section will describe the major com-
ponents and the principles of operation of the con-
trollable reversible pitch (CRP) propeller (a part
of the main propulsion system).
COMPONENTS OF THE CRP
Most ships that use CRP propellers use two
independent units with their associated
mechanical, hydraulic, and electronic pitch con-
trol mechanisms, plus all the required valves and
seals. Some type ships require tubing and passages
for the discharge of prairie air through each pro-
peller blade. The CRP propellers form an integral
part of the ships two shaft main propulsion
system. Figure 4-6 shows the major components
of a single CRP propeller.
Figure 4-6.CRP Propeller Machinery.