Gyroscope
RESTRICTED
3
Character-
istics of
Gyros
4.
Laws of
Precess-
ion
Fig. 43
concentric inner
ring.
This ring is free to re-
volve in
pivot
bearings in
outer ring,
about an
axis which is
always at right angles to the axis
of rotation of
the wheel.
The outer ring like-
wise iS
free to revolve
in pivot bearings in a
supporting frame about
an axis which is always at
right angles to
the axis of rotation of the inner
ring.
With a universal mounting such as this, the
axis of the wheel
may be pointed
in any direction
by the touch of
the finger.
In the bombsight the movement of the gyro is
limited
by the
construction
of the sight.
The
reason
for
the
limitation of gyro movements is
because the
purpose of the sight is accomplished
without entire
freedom of movement of the gyro.
The inner gimbal ring is the housing which enclos-
es the rotor; the second gimbal ring is the car-
dan, and the third gimbal ring is the
sight case.
All of the practical applications of gyro-
scopes are based upon
two fundamental character-
istics, namely, "Gyroscopic Inertia" and "Precess-
ion".
When a gyroscope is subjected
to a couple or
a force
about an
axis at right angles to its axis
of rotation it
resists that couple
and the degree
of
resistance is proportional to the velocity with
which the gyro turns, or precesses, about a third
axis which
is called
the axis of precession.
resistance
continues until the gyro has
precessed
so that its plane of rotation coincides with the
plane of applied
couple or
force.
Then precession
ceases and with it all resistance to the applied
couple.
Rigidity of plane and fixity in space are
also characteristics of gyros.
1. lf a force is applied perpendicular to the
plane of rotation of a spinning gyro, its spin
precess ninety degrees in the direction
of rotation from
the point of applied
pressure.
2. If
a torque is applied
about one of the axes
a spinning gyro, its spin
axis will tend
align itself with that axis, and in the direction
of rotation.
A convenient way to remember the direction of
precession is to
regard the applied couple or tor-
a push acting at a single point on the rim
of a wheel.
This point will not move in
115