Page:Aerial Flight - Volume 2 - Aerodonetics - Frederick Lanchester - 1908.djvu/439



The Schlick marine gyroscope is a recent invention for preventing or minimising the rolling of ships at sea This apparatus, illustrated diagrammatically in Fig. 205, consists of a fly-wheel A, whose bearings B, B, are carried by the frame C, which in turn is mounted on gimbals or trunnions D. D, arranged transversely to the vessel, the axis of rotation under normal conditions being vertical. When the vessel attempts to roll in a sea-way the gyroscope rocks or precesses on its gimbals, and by its precession it counteracts the turning moment, which would otherwise give the vessel angular momentum about a longitudinal axis—in other words, would produce a rolling motion.

The action of the gyroscope is illustrated in the series of diagrams given in Fig. 206. The lettered diagrams (a), (b), (c), etc., represent the vessel in the various phases of a passing wave, the direction of the torque due to the slope of the wave being clockwise when the water is higher on the left-hand side and vice versa. The angular momentum communicated by this torque appears in the momentum of aspect (comp. Appendix VII.) of the gyroscope, instead of appearing in the rolling of the vessel, as would under ordinary conditions be the case. Thus, referring to Fig. 206 (a), we have a condition of maximum clockwise torque, and the gyroscope is precessing in such a manner as to exhibit clockwise momentum as at (b), the maximum condition being reached when, as at (c), the applied torque has fallen to zero. The wave surface then begins to slope