Figure 4-1.--The gyroscope.

movement. The spinning mass is provided by a heavy

the second degree of freedom. The outer gimbal ring is

rotor. Figure 4-1 illustrates a free gyroscope. As you can

free to turn about the vertical or Z axis, the third degree

see in the figure, the rotor axle is supported by two

of freedom.

bearings in the horizontal ring,. This ring is supported by

two studs mounted in two bearings in the larger vertical

GYROSCOPIC PROPERTIES

ring. These two rings are called the inner gimbal and

outer gimbal, respectively. The outer gimbal is then

When a gyroscope rotor is spinning, it develops two

mounted with two studs and bearings to a larger frame

characteristics, or properties, that it does not possess

called the case.

when at rest: rigidity of plane and precession. These two

properties make it possible to convert a free gyroscope

The rotor and both gimbals are pivoted and balanced

into a gyrocompass.

about their axes. The axes (marked X, Y, and Z) are

perpendicular to each other, and they intersect at the

Rigidity of Plane

center of gravity of the rotor. The bearings of the rotor

and two gimbals are essentially frictionless and have

When the rotor of the gyroscope is set spinning with

negligible effect on the operation of the gyroscope.

its axle pointed in one direction (fig. 4-2, view A), it will

THREE DEGREES OF FREEDOM

As you can see in figure 4-1, the mounting of the

gimbals allows movement in three separate directions,

or three degrees of freedom: (1) freedom to spin, (2)

freedom to tilt, and (3) freedom to turn. The three

degrees of freedom allow the rotor to assume any

position within the case. The rotor is free to spin on its

own axis, or the X axis, the first degree of freedom. The

inner gimbal is free to tilt about the horizontal or Y axle,

Figure 4-1.--The gyroscope.

Figure 4-2.--Rigidity of plane of a spinning gyroscope.

4-2