line passing through the center of the gyroscope and
parallel to the earth's axis. This apparent rotation is in a
counterclockwise direction when viewed from south to
north. The path that the north axle describes in space is
indicated by the line EAWB back to E (fig. 4-10).
The effect of the earth's rotation causes the north
end of the gyroscope axle to rise when east of the
meridian and to fall when west of the meridian in any
latitude. This tilling effect provides the means by which
the gyroscope can be made into a north-seeking
MAKING THE GYROSCOPE INTO A
Up to this point, we have discussed the basic
properties of a free gyroscope. Now, we will discuss
how we use these properties, rigidity of plane and
precession, to make a gyroscope into a gyrocompass.
Figure 4-9.--Apparent rotation of a gyroscope at 45N
The first step in changing the gyroscope to a
gyrocompass is to make a change in the suspension
system. The inner gimbal that holds the gyro rotor is
modified by replacing it within a sphere or case (fig.
(aligned north-south) and parallel to the earth's surface
4-11, view A), a necessary feature that protects the rotor.
at 45 north latitude and 0 longitude (fig. 4-9).
A vacuum is formed inside the sphere to reduce air
A gyroscope, if set on any part of the earth's surface
friction on the spinning rotor. The next step is to replace
with the spinning axle not parallel to the earth's polar
the simple gyroscopic hose with what is called a
phantom ring (fig. 4-11, view A). The difference
axis, appears to rotate, over a 24-hour period, about a
Figure 4-10.--Path of the spinning axis of a free gyroscope.