Due to magnetic storms and any number of other causes the magnetic
compass may at any time be distracted so that it does not indicate
correctly. Disturbances are extraneous and their direction and
magnitude cannot be determined. The navigator is constantly subject to
the feeling that his compass may not be accurate—that he cannot depend
on it.
About the only thing that will cause an error in the Gyro-Compass is
the failure of the electrical power supply. Should this contingency
occur an electric bell warns the navigator. Any disturbances must
originate with the master compass and can be quickly and accurately
located.
* * * * *
The Sperry Gyro-Compass unfailingly points True North under all
conditions of weather, ship or cargo. It relieves the navigator of
calculation of errors, and tiresome compass compensations. It makes a
great saving in time required to “swing ship.” The Sperry Gyro-Compass
is, therefore, the Ideal Compass.
[Illustration]
[Illustration: The Great Eastern laid the first Atlantic cable.]
_Advantages Attending the Use of the Sperry Gyro-Compass_
During the construction of a steel ship it is usual to build it on ways
the direction of which lie in the East-West line. Should the ways be
placed in a North-South line the riveting on the keel and plates tends
to help the molecules of metal to place themselves parallel to the
magnetic lines of force, and magnetize the metal. When placed in the
East-West line the molecules of metal in the plates are at right angles
to the magnetic lines of force, and are not as easily magnetized. The
use of the Gyro-Compass eliminates the necessity of placing the ways in
the East-West line.
After a large ship has been launched, and during the fitting out
period, it is often necessary to have it swung end for end in order to
neutralize or equalize the magnetism induced by the earth’s magnetic
field. To swing a large ship end for end costs anywhere from one
thousand ($1000) to three thousand ($3000) dollars. The Gyro-Compass
is unaffected by any magnetic phenomena, and is so dependable that it
makes the swinging of the ship unnecessary.
In constructing a ship it is customary to make all metal parts within
approximately ten (10) feet of the magnetic-compass stand of bronze,
brass or other non-magnetic material. The proximity of magnetic metals
seriously affects the accuracy of the compass. All electric leads are
run so as to clear the vicinity of the compass, as the magnetic fields
set up by such conductors seriously influence the compass needle.
Actual experience is on record that the total installation cost of the
Sperry Gyro-Compass has been saved many times over by the elimination
of special metals and special run of electric leads.
[Illustration: Gyro-Compass School for Training Ship’s Officers and
Men.]
Before starting on a long voyage, especially with a new ship using the
magnetic compass, it is customary to swing the ship through a complete
circle to check deviation. To swing ship it is first necessary to pick
out a suitable object on land having a known bearing to the ship.
This object is used as a reference point. If at sea observations are
taken on the sun. The ship is then swung through 360 degrees, stopping
usually on each 15-degree heading, and noting the deviation. A table
is made up showing the deviation on each of these headings. An attempt
is then made to so adjust or manipulate the compensating magnets to
eliminate the error found. The ship must then again be swung through
360 degrees, stopping at headings as before to check the applied
compensation.
[Illustration: A Stern-wheeler of early steam-boating days.]
On some ships it is the custom to check the deviation by the deflector
magnet method. The ship in this case is put on a certain heading and a
magnet placed to one side of the compass and the deviation noted. The
same magnet is then placed at an equal distance to the opposite side
and the deviation noted. The difference, if any, between the readings
is the deviation on that particular course.
With either method of checking for deviation, considerable time
is used. It is not necessary to check for deviation or apply any
compensation to the Gyro-Compass, as it is not magnetic. In fact the
Gyro-Compass has nothing whatever to do with magnetism.
When at sea the Gyro-Compass affords the means of keeping to the
straight-line, true course. The line A B, Figure 5, shows the
straight-line course from the port of New York to the port of
Liverpool. The line A C E B shows, with exaggeration, the actual course
steered due to compass and other errors. At the point E the ship’s
position was checked by observation of a celestial body. The line E B
represents the new course set to bring the ship to her destination.
This is an occurrence which sometimes happens not once but often during
a voyage.
[Illustration: Figure 5. Errors of Magnetic Compass Cause Departure
From Desired Course.]
It is evident that a loss of time is involved when the ship leaves her
straight line course. The inherent accuracy of the Sperry Gyro-Compass
enables the ship to keep to the straight line course, and also to steer
directly on true courses.
By keeping on a straight line course the ship is enabled to make a
good many more miles on the same number of revolutions or turns of
the propeller. Under exactly the same weather conditions a 16,000 ton
liner made 370 miles in 24 hours at an average of 86.95 revolutions per
minute per mile when steered by a magnetic compass, and the same liner
made 377 miles with 85.61 revolutions per minute per mile when steered
by the Gyro-Compass. This saving amounts to easily $50 per day for this
ship. During her eleven-day voyage she saved $550. At this rate of
saving the Gyro-Compass equipment is soon paid for.
[Illustration: Steering Repeater in Wheel House.]
[Illustration: The Turbinia was the first turbine steamer.]
The Sperry Gyro-Compass does not oscillate with the rolling of the
ship, or in other words, has no heeling error. The use of the helm
is greatly diminished. Records show that on one trans-Atlantic liner
a saving of 24 percent in the revolutions of the steering engine,
when steered by Gyro-Compass, was effected. One of the largest
trans-Atlantic liners reports that but one-third of the helm is used
when the ship is steered by Gyro-Compass.
This saving in the use of the steering engine gives actual proof that
the ship navigated by a Gyro-Compass steers a straight line course.
It further proves that the ship does not divert its slip-stream as
often—the power output of the main engines is thereby reduced.
Records taken on a well-known passenger liner show that in making her
regular trip between New York and Jacksonville, Florida, she saved more
than two hours due to steering by a Sperry Gyro-Compass. A saving of
3,410 turns of her propeller was also effected. These savings were made
even with much greater than the usual draft.
Records taken by means of the Sperry Recording Compass show that when
the helmsman is given a certain course he can keep the ship one and
one-half degrees nearer the course when steering by the Gyro-Compass
than when steering by magnetic compass.
The Gyro-Compass can make great savings in money both in construction
and operation of the ship. These factors are perhaps trivial when
compared with the safety factor introduced by the use of the Sperry
Gyro-Compass.
[Illustration: High Potential Test on Repeaters.]
Due to the elimination of the many uncertainties of the magnetic
compass, insurance companies are favorably disposed toward the use of
the Sperry Gyro-Compass, which ultimately will result in a reduction of
insurance rates.
The use of the Sperry Gyro-Compass eliminates inaccuracies due to
navigation, thereby saving time, insuring the ship, the cargo, and the
lives of passengers and crew.
Sperry Gyro-Compasses are operating on many of the world’s largest
and fastest passenger liners and cargo ships. These ships are making
savings every day of fuel used and time required to make their courses.
The navigators using these compasses find that they can come very much
nearer their calculated positions when steering by the Gyro-Compass.
The Gyro-Compass makes the art of navigation more exact.
The Sperry Gyro-Compass is the only one to pass the service tests in
the world’s navies.
[Illustration: Schooners are economical, needing but small crews.]
_The Sperry Gyro-Compass Equipment_
The equipment which applies the principle set forth in a practical way
consists of: