in motor trucks. Friction clutches may be single-cone or
double-cone. Figure 11-25, D, shows a disc clutch, also
used in autos. A disc clutch also may have several plates
(multiple-disc clutch). In a series of discs, each driven
disc is located between two driving discs. You may have
had experience with a multiple-disc clutch on your car.
The Hele-Shaw clutch is a combined conical-disc
clutch (fig. 11-25, E). Its groove permits cooling and
circulation of oil. Single-disc clutches are frequently dry
clutches (no lubrication); multiple-disc clutches may be
dry or wet (either lubricated or operated with oil).
Magnetic clutches are a recent development in
which the friction surfaces are brought together by
magnetic force when the electricity is turned on (fig.
11-25, F). The induction clutch transmits power without
contact between the driving and driven parts.
The way pressure is applied to the rim block, split
ring, band, or roller determines the names of expanding
clutches or rim clutches. In one type of expanding
clutch, right- and left-hand screws expand as a sliding
sleeve moves along a shaft and expands the band against
the rim. The centrifugal clutch is a special application
of a block clutch.
Machines containing heavy parts to be moved, such
as a rolling mill, use oil clutches. The grip of the coil
causes great friction when it is thrust onto a cone on the
driving shaft. Yet the clutch is very sensitive to control.
Diesel engines and transportation equipment use
pneumatic and hydraulic clutches. Hydraulic couplings
(fig, 11-25, G), which also serve as clutches, are used in
the hydraulic A-end of electric-hydraulic gun drives.
In this chapter we discussed the following elements
and mechanisms used in naval machinery:
Two types of bearings are used in naval machinery:
sliding and antifrictional.
Springs are another element used in machinery.
Springs can be twisted, pulled, or stretched by
force and can return to their original shape when
the force is released.
One basic mechanism of machines is the gear
differential. A gear differential is a mechanism
that is capable of adding and subtracting
mechanically. Other basic mechanisms include
linkages, couplings, cams and cam followers,