gyroscopic

gyroscopic, or gyro, compass, an electrically driven compass that owes its directional properties to a perfectly balanced wheel, or rotor, that spins at high speed symmetrically about an axis. The operation of the gyro compass depends on four phenomena: (1) gyroscopic inertia which enables the rotor to maintain the direction of its plane of rotation unless an external force of sufficient amplitude alters its direction; (2) gyroscopic precession which causes movement at 90° to any applied force; (3) gravity; and (4) the rotation of the earth. Unless subjected to any external force the perfect gyroscope will continue to point in the same direction in space. Gravity and the rotation of the earth are used in the gyro compass, with gyroscopic inertia and precession, to give the gyroscope its north-seeking properties which have given the instrument its unique advantage.

The gyro compass has now replaced the magnetic compass in virtually all commercial shipping. It is not affected by magnetism so that compass adjustment is no longer necessary, nor corrections from compass to true bearings. Repeaters are normally driven by the master gyro compass for use on the bridge and to feed electronic equipment such as radar and electronic dead reckoning instruments. A minor disadvantage of the gyro compass is that it takes, typically, 75 minutes to settle down after it has been switched on.

The first successful gyroscopic compass, which was introduced in 1908, was invented by the German engineer Dr Anschütz- Kaempfe for use in an underwater vehicle. In 1911 the American Dr Elmer Sperry patented his gyroscopic compass, and some five years later the British scientist and inventor S. G. Brown introduced a similar compass.

Mike Richey