Strut Bearings

Chapter 4—REDUCTION 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.“, “Submarine”). STRUT BEARINGS 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 the strut. 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 qualities; 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 PROPELLER 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 ship’s two shaft main propulsion system. Figure 4-6 shows the major components of a single CRP propeller. Figure 4-6.—CRP Propeller Machinery. 4-11