TM 1-1500-204-23-1
Figure 7-7. Radial-Type Crankshaft (Single-Throw)
c.
Bearings. A beanng is any surface which
supports, or is supported by, another surface. A good
bearing must be composed of a metal that is strong
enough to withstand the pressure imposed on it and
should permit the other surface to move with a minimum
of friction and wear. The parts must be held in position
within very close tolerances to provide efficient and quiet
operation, and yet allow freedom of motion. To
accomplish this, and at the same time reduce friction of
moving parts so that power loss is not excessive,
lubricated bearings of many types are used.
(1)
Types. The three different types of
bearings in general use are plain, roller and ball They are
shown in figure 7-8 and described in the following
paragraphs.
(a)
Plain bearings. Plain bearings are
usually made of nonferrous metals, such as silver,
bronze, aluminum, and various alloys of copper, tin, or
lead. Plain bearings are generally used for the
crankshaft, cam ring, camshaft, connecting rods, and the
accessory drive shaft bearings.
(b)
Ball bearings A ball beanng
assembly consists of grooved Inner and outer races, one
or more sets of balls, and in bearings designed for
disassembly, a bearing retainer They are used for
supercharger Impeller shaft beanngs and rocker arm
bearings in some engines. Special deep-groove ball
bearings are used in
Figure 7-8. Bearing Types
aircraft engines to transmit propeller thrust to the engine
nose section
(c)
Roller bearings Roller bearings are
made In many types and shapes, but the two types
generally used in the aircraft engine are the straight roller
and the tapered roller beanngs. Tapered roller bearings
are always used In pairs Straight roller
7-5
