3-7
Q-8. Which gyro rotor in figure 3-6, view (A) view (B) view (C), will have the greatest rigidity if all
are rotated at the same speed?
PRECESSION
To provide useful information, a gyro's spin axis must be related to some reference, usually the
Earth's surface. This is done by using the second fundamental property of a gyro—PRECESSION. The
gyro is precessed until its spin axis is pointed in the desired direction. So far we have covered precession
in very general terms. The following paragraphs will cover this "gyro action" in more detail.
We can show precession by using the models in figure 3-7, view (A) and view (B). The gyro wheel
is mounted so it is free to have its spin axis pointed in any direction. Here the wheel rotates in a flat loop
called the gyro case (inner gimbal). The gyro case is pivoted in the gimbal ring (outer gimbal) and the
gyro can swing about the Z axis. The gimbal ring itself turns on pivots that connect it to the fork
(support). The fork permits the gyro to tilt from side to side about the Y axis.
Figure 3-7A.—Gyro action.
