Gyro Compass on Ships: Construction,
Working, and Usage
A Gyro compass is a form
of gyroscope, used widely on ships employing an electrically powered,
fast-spinning gyroscope wheel and frictional forces among other factors
utilizing the basic physical laws, influences of gravity and the Earth’s
rotation to find the true north.
Construction
Gyro compass has become one indispensable instrument in almost
all merchant ships or naval vessels for its ability to detect the direction
of true north and not the magnetic north. It is comprised of the following
units:
§
Master Compass: Discovers and
maintains the true north reading with the help of 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
constant supply of the ship 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 energizes 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 thousands of
revolutions per minute by another electric motor. However, the most essential
part in a Gyro compass system is the spinning wheel, which is known as the
Gyroscope.
Working
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 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 so that it can move freely about three
mutually perpendicular axes and is controlled as to enable its axis of spin
settled parallel with the true meridian, influenced by the Earth’s rotation and
gravity. The Gyro compass 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. But instead of moving
in the direction of the couple, it moves at right angles to the axis of the
applied couple and also the spinning wheel.
These two properties
and the utilization of the Earth’s two natural forces, rotation and gravity,
enacts the Gyrocompass seek true north. Once settled on the true meridian the
rotor indefinitely will remain there as long as the electrical supply of the
ship remains constant and unaltered and unaffected by external forces.
Usage and Errors
Gyro compasses are
pre-eminently used in most ships in order to detect true north, steer, and find
positions and record courses. But due to the ship’s course, speed and latitude,
there could appear 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 feed data to
the Gyrocompass for correcting the error. An orthogonal triad of fibre optic
design and also ring laser gyroscopes which apply the principles of optical
path difference to determine rate of rotation, instead of depending upon
mechanical parts, may help eliminate the flaws and detect true north.
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