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