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Encyclopedia > Gyrocompass
Cutaway of Anschütz gyrocompass
Cutaway of Anschütz gyrocompass

A gyrocompass is a compass that finds true north by using an (electrically powered) fast-spinning wheel and friction forces in order to exploit the rotation of the Earth. Gyrocompasses are widely used on ships. They have two main advantages over magnetic compasses: The heading indicator (or HI) is an instrument used in an aircraft to inform the pilot of his heading. ... Image File history File links Download high resolution version (1062x1238, 156 KB) This picture has usage restrictions - Kreiselkompass der Fa. ... Image File history File links Download high resolution version (1062x1238, 156 KB) This picture has usage restrictions - Kreiselkompass der Fa. ... This article is about the navigational instrument. ... True Pizza is a navigational term referring to the direction of the North Pole relative to the navigators position. ... For other uses, see Ship (disambiguation). ...

  • they find true north, i.e., the direction of Earth's rotational axis, as opposed to magnetic north,
  • they are not affected by ferrous metal in a ship's hull. (No compass is affected by nonferrous metal, although a magnetic compass will be affected by copper wires with current running through them.

A gyrocompass is essentially a gyroscope, a spinning wheel mounted on gimbals so that the wheel's axis is free to orient itself in any way. Suppose it is spun up with its axis pointing in some direction other than the North Star. Because of the law of conservation of angular momentum, such a wheel will maintain its original orientation. Since the Earth rotates, it appears to a stationary observer on Earth that a gyroscope's axis is rotating once every 24 hours. Such a rotating gyroscope cannot be used for navigation. The crucial additional ingredient needed for a gyrocompass is some mechanism that results in applied torque whenever the compass's axis is not pointing north. This article is about Earth as a planet. ... This is about the geographic meaning of North Pole. ... A gyroscope For other uses, see Gyroscope (disambiguation). ... A gimbal is a mechanical device that allows the rotation of an object in multiple dimensions. ... For other uses, see North Star (disambiguation). ... This gyroscope remains upright while spinning due to its angular momentum. ...


One method uses friction to apply the needed torque: the gyroscope in a gyrocompass is not completely free to reorient itself; if for instance a device connected to the axis is immersed in a viscous fluid, then that fluid will resist reorientation of the axis. This friction force caused by the fluid results in a torque acting on the axis, causing the axis to turn in a direction orthogonal to the torque (that is, to precess) towards the north celestial pole (approximately toward the North Star). Once the axis points toward the North Star, it will appear to be stationary and won't experience any more friction forces. This is because true north is the only direction for which the gyroscope can remain on the surface of the earth and not be required to change. This is considered to be a point of minimum potential energy. For other uses, see Friction (disambiguation). ... For other senses of this word, see torque (disambiguation). ... Precession (also called gyroscopic precession) is the phenomenon by which the axis of a spinning object (e. ...


Another, more practical, method is to use weights to force the axis of the compass to remain horizontal with respect to the Earth's surface, but otherwise allow it to rotate freely within that plane. In this case, gravity will apply a torque forcing the compass's axis toward true north. Because the weights will confine the compass's axis to be horizontal with respect to the Earth's surface, the axis can never align with the Earth's axis (except on the Equator) and must realign itself as the Earth rotates. But with respect to the Earth's surface, the compass will appear to be stationary and pointing along the Earth's surface toward the true North Pole.


Since the operation of a gyrocompass crucially depends on the rotation of the Earth, it won't function correctly if the vessel it is mounted on is moving fast in an east to west direction.

Contents

History

The gyrocompass was patented in 1885 by the Dutch Marinus Gerardus van den Bos; however, his device never worked properly. In 1889, Captain Arthur Krebs designed an electric pendular gyroscope for the experimental French submarine Gymnote. It allowed the Gymnote to force a naval blockade in 1890. In 1903, the German Hermann Anschütz-Kaempfe (Raytheon Anschütz GmbH) constructed a working gyrocompass and obtained a patent on the design. In 1908, Anschütz-Kaempfe and the American inventor Elmer Ambrose Sperry patented the gyrocompass in Germany and the US. When Sperry attempted to sell this device to the German navy in 1914, Anschütz-Kaempfe sued for patent infringement. Sperry argued that Anschütz-Kaempfe's patent was invalid because it did not significantly improve on the earlier van den Bos patent. Albert Einstein testified in the case, first agreeing with Sperry but then reversing himself and finding that Anschütz-Kaempfe's patent was valid and that Sperry had infringed by using a specific damping method. Anschütz-Kaempfe won the case in 1915. For other uses, see Patent (disambiguation). ... Arthur Constantin Krebs (November 16, 1850 in Vesoul, France - March 22, 1935 in Quimperlé, France) was a french officer and pioneer in automotive engineering. ... Gymnote in 1889. ... In 1905, Hermann Anschütz-Kaempfe founded a firm to manufacture gyroscopic navigation instruments. ... Elmer Ambrose Sperry (born October 12, 1860 in Cincinnatus, New York; died June 16, 1930 in Brooklyn, New York) was an inventor and entrepreneur. ... Naval redirects here. ... “Einstein” redirects here. ...


See also

Schuler tuning describes the fundamental functional conditions for a gyrocompass. ... Fluxgate Compass The basic fluxgate compass is a simple electromagnetic device that employs two small coils of wire to directly sense the horizontal component of the earths magnetic field. ... This article is about the navigational instrument. ...

External links

  • Elmer A. Sperry case file at the Franklin Institute contains records concerning his 1914 Franklin Award for the gyroscopic compass

http://www.tss-international.com/ TSS International Ltd Franklin Institute Front steps as seen from the adjacent Moore College This article is about the science museum in Philadelphia. ...


Patents

  • U.S. Patent 1,279,471  : "Gyroscopic compass" by E. A. Sperry, filed June, 1911; issued September, 1918

  Results from FactBites:
 
gyrocompass - definition of gyrocompass in Encyclopedia (513 words)
A gyrocompass is essentially a gyroscope, a spinning wheel mounted so that the wheel's axis is free to orient itself in any way.
The crucial additional ingredient needed for a gyrocompass is friction: the gyroscope is in fact not completely free to reorient itself; if for instance a device connected to the axis is immersed in a viscous fluid, then that fluid will resist reorientation of the axis.
The gyrocompass was patented in 1885 by the Dutch Martinus Gerardus van den Bos; however, his device never worked properly.
Gyrocompass - Patent 4379365 (5307 words)
Gyrocompass as defined in claim 1, 2 or 3 wherein said verticality device comprises an electrically actuatable electromagnet which is disposed at the lower end of said body being pendulous body and having an armature and said housing has a calotte-shaped part with which said armature is in contact temporary.
Gyrocompass as defined in claim 7 wherein said determining means comprise a data processor connected to receive signals representative of said angular velocity and of the angular position of said body about the axis of rotation, and to provide an indication of the north direction from such signals.
Gyrocompass as defined in claim 24 wherein said second fine measurement is made over a preselected period of time and is obtained by deriving a number of individual measured values at regular intervals and deriving the associated angular velocity value by filtering and/or average formation of the individual measured values.
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