The course corrector cam consists of a circular groove in the under face of the azimuth gear, Z, Fig. 154. The groove is eccentric relative to the azimuth gear. In this groove fits a roller C on the end of a bent lever PQ, Figs. 165 and 166. The other end of the bent lever fits into the lower end of a vertical lever RT, Fig. 166, capable of rotation about a pin S. This pin can be moved up or down by means of a screw, K, Figs. 155 and 165, thereby changing the lever arm ST, Fig. 166. A displacement of the end T rotates the lever UV about a fixed pin U, thereby shifting the lubber ring attached to XX' by an amount which depends upon the lengths of the various lever arms. The lever PQ allows
for the quantity a cos 0. The allowance for cos X
is made by a
proper setting of the pin S. This setting is effected by adjusting the screw K, Fig. 165, until the correct latitude reading on the horizontal scale M is on the correct speed curve engraved on the face plate N, Figs. 156 and 165. The speed curves are obtained empirically.
By thus shifting the lubber line to the proper amount, the ship will point correctly but the compass will not. In taking bearings of heavenly bodies, or of points on the shore, it is necessary to know true directions. True directions can be Qbtained by means of a repeater compass electrically connected to a transmitting device mounted on the lubber ring of the master compass (Art. 127).
124. Avoidance of the Ballistic Deflection Error. - In the Sperry gyro-compass models designated Mark V, Mark VI, Mark VII and Mark VIII, the period of vibration of the sensitive ele-