Appendix VIIId
The Gyroscope for Direction Maintenance—the Whitehead Torpedo
The gyroscope in the Whitehead torpedo differs as to its mode of employment from the preceding examples; its function here is purely directive, it is not in any way concerned with the maintenance of equilibrium.
In brief, the gyroscope is mounted in a similar manner to a lecture model, on double gimbals, so that it is unaffected by the rotational movements of its surroundings; the torpedo may change its course upward or downward, or to the right or left, without the axis of rotation of the gyroscope undergoing any change of direction. The outer gimbal of the mounting is arranged to actuate a small rotary valve which controls the admission of air to a pneumatic cylinder; thus the gyroscope is utilised as if it were an accurately suspended mass of great moment of inertia.
In order to obtain a clear idea of the action of the above combination it is convenient to regard the rotary valve as being rigidly attached to one of the outer ring trunnions of the gyroscope, and so as being fixed in space, whilst the valve case is fixed to the torpedo and shares with the latter any change of course; then, every time the torpedo from any cause tries to depart from the ordained course, it moves the valve case round relatively to the valve (the latter being held stationary by the gyroscope), and so admits air under 250 lbs, pressure to the
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