[Illustration: THE GYROSCOPE]
This device for automatic control is being steadily developed and may
ultimately supersede all others. It uses the inertia of a fast-moving
fly wheel for control, in a manner not unlike that contemplated in
proposed methods of automatic balancing by the action of a suspended
pendulum. Every one has seen the toy gyroscope and perhaps has wondered
at its mysterious ways. The mathematical analysis of its action fills
volumes: but some idea of what it does, and why, may perhaps be
gathered at the expense of a very small amount of careful attention.
The wheel _acbd_, a thin disc, is spinning rapidly about the axle _o_.
In the side view, _ab_ shows the edge of the wheel, and _oo´_ the
axle. This axle is not fixed, but may be conceived as held in some
one's fingers. Now suppose the right-hand end of the axle (_o´_) to
be suddenly moved toward us (away from the paper) and the left-hand
(_o_) to be moved away. The wheel will now appear in both views as an
ellipse, and it has been so represented, as _afbe_. Now, any particle,
like _x_, on the rim of the wheel, will have been regularly moving
in the circular orbit _cb_. The tendency of any body in motion is to
move indefinitely in a straight line. The cohesion of the metal of
the disc prevents the particle _x_ from flying off at a straight line
tangent, _xy_, and it is constrained, therefore, to move in a circular
orbit. Unless some additional constraint is imposed, it will at least
remain in this orbit and will try to remain in its plane of rotation.
When the disc is tipped, the plane of rotation is changed, and the
particle is required, instead of (so to speak) remaining in the plane
of the paper--in the side view--to approach and pass through that plane
at _b_ and afterward to continue receding from us. Under ordinary
circumstances, this is just what it would do: but if, as in the
gyroscope, the axle _oo´_ is perfectly free to move in any direction,
the particle _x_ will refuse to change its direction of rotation.
Its position has been shifted: it no longer lies in the plane of the
paper: but it will at least persist in rotating in a parallel plane:
and this persistence forces the revolving disc to swing into the new
position indicated by the curve _hg_, the axis being tipped into the
position _pq_. The whole effect of all particles like _x_ in the entire
wheel will be found to produce precisely this condition of things: if
we undertake to change the plane of rotation by shifting the axle in
a horizontal plane, the device itself will (if not prevented) make
a further change in the plane of rotation by shifting the axle in a
vertical plane.
A revolving disc mounted on the gyroscopic framework therefore resists
influences tending to change its plane of rotation. If the device
is placed on a steamship, so that when the vessel rolls a change of
rotative plane is produced, the action of the gyroscope will resist
the rolling tendency of the vessel. All that is necessary is to have
the wheel revolving in a fore and aft plane on the center line of the
vessel, the axle being transverse and firmly attached to the vessel
itself. A small amount of power (consumed in revolving the wheel) gives
a marked steadying effect. The same location and arrangement on an
aeroplane will suffice to overcome tendencies to transverse rotation
when rounding curves. The device itself is automatic, and requires no
attention, but it does unfortunately require power to drive it and it
adds some weight.
The gyroscope is being tested at the present time on some of the
aeroplanes at the temporary army camps near San Antonio, Texas.