3-1
CHAPTER 3
GYROS
LEARNING OBJECTIVES
Upon completion of this chapter you should be able to:
1. Describe the characteristics of a gyroscopes.
2. List the two basic properties of gyroscopes and explain them.
3. Describe the components of a universally mounted gyro.
4. Describe the factors that determine rigidity in a gyro.
5. List the factors that determine the direction of precession in a gyro.
6. Explain the right-hand rule for gyro precession.
7. Describe the term "Degree of Freedom" as it applies to gyros.
8. Explain the effect of apparent precession (apparent rotation).
9. Explain the purposes of erection systems.
10. Describe the use of gyros with only one degree of freedom.
11. Explain the purpose of an accelerometer.
12. Explain the principle on which accelerometers operate.
13. Explain the need for a pulse-counting accelerometer.
GYROS
The word gyroscope was first coined by a French scientist, Leon Foucault, in 1852. It is derived
from the Greek words "gyro," meaning revolution, and "skopien," meaning to view.
The gyroscope, commonly called a GYRO, has existed since the first electron was sent spinning on
its axis. Electrons spin and show all the characteristics of a gyro; so does the Earth, which spins about its
polar axis at over 1000 miles per hour at the Equator. The Earth's rotation about its axis provides the
stabilizing effect that keeps the North Pole pointed within one degree of Polaris (the North Star).
Any rapidly spinning object—a top, a wheel, an airplane propeller, or a spinning projectile—is
fundamentally a gyroscope. Strictly speaking, however, a gyroscope is a mechanical device containing a
spinning mass that is universally mounted; that is, mounted so it can assume any position in space. Figure
3-1 shows a model of a gyro. As you can see, a heavy wheel (rotor) is mounted so that its spin axis is free
to turn in any direction. The wheel spins about axis X; it can turn about axis Y, and it can turn about axis
Z. With this mechanical arrangement, the spinning wheel can assume any position in space.
