Gyro Compass On Ships: Construction, Working, And Usage

 

A Gyro compass is a form of gyroscope, used widely on ships. It employs an electrically powered, fast-spinning gyroscope wheel and frictional forces, among other factors, to find the true north, utilising the basic physical laws, influences of gravity, and the Earth’s rotation.

Construction of Gyro Compass

The marine gyro compass has become an indispensable instrument in almost all merchant ships and naval vessels, as it is capable of detecting true north rather than magnetic north. It is comprised of the following units:

• Master Compass: Discovers and maintains the true north reading with the help of a gyroscope
• Repeater Compasses: Receive and indicate the true direction transmitted electrically from the Master Compass.
• Course Recorder: Makes a continuous record of the manoeuvring on a moving strip of paper.
• Control Panel: Governs the electrical operation of the system and ascertains the running condition by means of a suitable meter.
• Voltage Regulator: Maintains a constant supply of power to the motor-generator.
• Alarm Unit: Indicates failure of the ship’s supply.
• Amplifier Panel: Controls the follow-up system.
• Motor Generator: Converts the ship’s DC supply to AC and energises the Compass equipment.

Gyro compasses are linked to the repeater compasses via one transmission system. The fast-spinning rotor attached weighs from 1.25 pounds to 55 pounds.

It is driven by thousands of revolutions per minute by another electric motor. However, the most essential part of a Gyro compass system is the spinning wheel, known as the Gyroscope.

Working of Gyro Compass

External magnetic fields which deflect normal compasses cannot affect Gyro compasses. When a ship alters its course, the independently driven framework called ‘Phantom’ moves with it, but the rotor system continues to point northward.

This lack of alignment enables it to send a signal to the driving motor, which moves the phantom step in with the rotor system again in a path where the phantom may have crossed only a fraction of a degree or several degrees of the compass circle.

As soon as they are aligned, electrical impulses are sent by the phantom to the repeater compasses for each degree it traverses.

The Gyroscope in the Gyrocompass is mounted in such a way that it can move freely about three mutually perpendicular axes and is controlled to enable its axis of spin to settle parallel with the true meridian, influenced by the Earth’s rotation and gravity.

The Gyrocompass system applications are based upon two fundamental characteristics, which are:

• Gyroscopic Inertia: The tendency of any revolving body to uphold its plane of rotation.

• Precession: A property that causes the gyroscope to move when a couple is applied. Instead of moving in the direction of the couple, it moves at right angles to the axis of the applied couple and the spinning wheel.

These two properties and Earth’s natural forces of rotation and gravity allow the Gyrocompass to seek true north.

Once settled on the true meridian, the rotor will indefinitely remain there as long as the electrical supply of the ship remains constant and unaffected by external forces.

 

Usage and Errors

Gyro compasses are preeminently used in most ships to detect true north, steer, find position and record courses.

But due to the ship’s course, speed and latitude, there could be some steaming errors. It has been found that on Northerly courses the Gyro compass north is slightly deflected to the West of the true meridian, whereas on Southerly courses it is deflected to the East.

Modern ships use a GPS system or other navigational aids to feed data to the Gyrocompass for correcting the error. An orthogonal triad of fibre optic design and ring laser gyroscopes, which apply the principles of optical path difference to determine the rate of rotation, instead of depending upon mechanical parts, may help eliminate flaws and detect true north.

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