Figure 4-12.--Effect of weight and earth's rotation on the gyroscope.

Figure 4-12.--Effect of weight and earth's rotation on the gyroscope.

W and W1, influence the gyro when it is not aligned with

soon as it tilts, weight W causes precession; however,

now the smaller weight, W1, also causes the gyro to

the meridian (fig. 4-13).

precess towards a more level position, which limits the

When the gyro is started while pointed away from

effect of precession caused by weight W. The excursions

the meridian, the effect of earth rate causes it to tilt. As

from level continue, but the dampening effect of weight

W1 causes each successive oscillation to be reduced; the

path of the rotor axle then will be spiral shaped (fig.

As you can see, the only position of rest for the gyro

axle is level and on the meridian. The free gyroscope

has now become a gyrocompass, able to settle only on

the meridian (pointing north) and level.

This is a very basic gyrocompass, and it really

operates satisfactorily only on the equator and when

mounted on a stable platform; however, the principles

and basic concepts are the same for all gyrocompasses.

To make a basic gyrocompass function properly

over a wide range of latitudes, we must stabilize it with

Figure 4-13.--Gyroscope with weights on the vertical ring and

respect to the earth's surface instead of with the earth's

sphere.

axis, and we must damp out the effects of the ship's

4-8