The Sperry Gyro-Compass. Sperry Gyroscope Company
of dollars are spent each year on charts, lighthouses, buoys, geodetic and hydrographic surveys, and on compilation of notices to mariners. Notwithstanding all of these, ships must ultimately depend upon their compasses for their safety and efficiency of navigation.
Inaccuracies in navigation can be eliminated by the use of a reliable compass. The Sperry Gyro-Compass puts the earth to work. It utilizes a force which is as unvarying as the law of gravity, a force that cannot be interfered with by any other influence.
How the Earth’s Rotation Is Utilized
Any wheel rotating at a high speed about its own axis, and free to place itself in any plane, is called a Gyroscope. The Gyroscope is the instrument which utilizes the earth’s rotation as a force to direct the course of ships.
Suppose you were to place such a small wheel supported by its axis upon a larger wheel which also is revolving. The rotation of the larger wheel would so influence the smaller wheel that its axis would point in the same direction as the axis of the larger wheel. Why this is the case does not concern us here. Let it suffice that the larger wheel will cause the smaller wheel to behave in this manner. This is in accordance with a natural law. This law operates as unfailingly as the law which causes an unsupported body to fall to the ground.
Suppose the larger wheel happens to be the earth, which in reality is a revolving wheel. Suppose further, the small wheel is a Sperry Gyro-Compass. In accordance with this natural law just outlined the smaller wheel, or Gyro-Compass, will point its axis in the same direction as the axis of the earth, or, in other words, to the true or geographical North Pole. This explanation of the principle of gyroscopic motion is necessarily crude. The principle itself has been established beyond any reasonable doubt. It can be proved by mathematics to the satisfaction of the most exacting scientist and has been demonstrated, throughout the navies of the world, to practical seamen.
The final result is that we have a principle which enables us to construct an instrument which will place itself in the true geographic north and south meridian, and that it responds to no influence or impulse other than the earth’s unvarying rotation.
Galley-slaves drove the Triremes of ancient Rome.
The Earth Surrounded By Rotating Wheels As It Appears To An Imaginary Observer Looking At It From The Side.
The Earth Surrounded By Rotating Wheels As It Appears To An Imaginary Observer Looking Directly At The South Pole
A War-ship, “when knighthood was in flower”.
How a Compass is Used
HE purpose of a compass is to indicate direction. The relative position of the North Pole to any point on the earth’s surface is called North. We figure all direction from this conception. This geographical North Pole is called the True North. About 800 miles from this True North Pole is a spot which has a strange magnetic attraction. The needle of the magnetic compass, if undisturbed by local influences, points to this spot, and not to the True North Pole. This spot is called the Magnetic North Pole. This mysterious attractive spot is not stationary. It moves about from year to year within a wide circle.
Inasmuch as the navigator must refer to True North, he must determine the angle or variation between True North and Magnetic North as indicated by his magnetic compass. This determination is made comparatively easy by using charts which express in degrees the difference between Magnetic North and True North for any point on the earth’s surface.
Such a chart is shown in Figure 3. Also on each chart used by a navigator for a particular locality there is marked a compass rose in which is recorded the variation for that exact spot as of a certain date, and in addition the rate at which the variation changes annually, Figure 4.
Navigation along a coast line where sights can be taken on buoys or lighthouses is simple, and is termed “piloting.” This, of course, can be done without the aid of a compass.
Upon getting to open sea the mariner checks his position in a similar manner, by observing the position of his ship in relation to the position of the sun, moon or stars. Between observations the position of a ship is determined by “dead reckoning.” The distance it has traveled from the last known position is measured by the ship’s log and the direction is indicated by the compass. Very often for days at a time, owing to weather conditions, it is impossible to get an observation or sight on a celestial body. During this run the navigator is dependent entirely upon the compass. The slightest error in the compass, due to variation or deviation, in such circumstances will cause the ship to be miles out of its course, and the actual position will be far from the calculated position.
The Santa Maria carried Columbus to the new world.
The Ideal Compass
F you were to conceive of a compass which would be free from all the troubles and errors found in most compasses, which would relieve you of all the worry and care the present compass requires, a compass which would be accurate and reliable, a compass which would be the Ideal Compass under all conditions, you would undoubtedly conceive of a compass that had the following characteristics:
1.It must point True North.
2.It must free you from the necessity of making calculations and corrections.
3.It must free you from compensating the compass for errors.
4.It must free you from the burden of swinging the ship, or otherwise taking the deviation of your compass.
5.It must not be influenced by inherent magnetism of the ship.
6.It must not be influenced by any change in the character or disposition of the cargo.
7.It must not be influenced directly or indirectly by any temperature changes.
8.It must not be influenced by the roll or pitch of the ship.
9.It must not be influenced by any weather conditions.
10.In the event of failure, or error, it should give instant warning.
Comparison of the Magnetic Compass with the Sperry Gyro-Compass