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## The Gyroscope Forum

16 February 2019 00:06

Welcome to the gyroscope forum. If you have a question about gyroscopes in general, want to know how they work, or what they can be used for then you can leave your question here for others to answer. You may also be able to help others by answering some of the questions on the site.

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Subject: how is a gyroscope made north seeking?
Question: hi everyone, i'd like to know how a gyroscope is made north seeking for use in a gyro compass. now i know about the rigidity in space n precession... as in, what they are n what they mean with ref. to a free gyroscope. its the effect that the earths rotation has on the free gyro scope that leaves me scratching my bald pate, particularly when the gyro is placed 1)on the equator 2) at the poles. i've tried searching for pages concerning the same on the net but came up with just the basic stuff (precession etc etc.).i need to know details about damping, top heavy n bottom heavy, their effect on the free gyro and how one goes about damping a free gyro n making it top heavy or bottom heavy. help would be much appreciated!!... a point in the right direction would do just as well... thanks a tonne!
Date: 8 August 2003
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Answer: Steve C - 11/08/2003 10:22:10
in aeroplanes, the directional gyro is alighned with magnetic north after you start the motor, and checked just prior to take off. We then recheck it in less busy or turbulent phases of flight using the onboard compass. You could use a big magnet ( theoretically) strapped to the gymbals of your gyro to make it seek north over a period of time, but that is more complicated than referring it occasionally to a seperate magnetic compass....

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I think the answer is "friction". If device is immersed in a fluid intriducing friction, the gyro will tend to come to a position of minimum friction, ie were gyro does not show anymore apparent movement to observer on the rotating surface of earth, ie when gyro spin axis is parrallel to earth rotational axis, ie when it point north.

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Answer: Brian Turner - 09/05/2004 01:03:30
There are many types of gyrocompasses. The ones used on ships need no magnets to find north and will find it pretty much on their own. The axis of the compass syncs with the axis of the earth. It will also tell you how far north or south you are. The Sperry gyrocompass is a good example. I can't find my engineering book that explained it so I'll describe it from memory. The gyro must be started generally pointing north or else it will take a long time to get accurate and might point south. A pendulum is hung from the gyro and limited so that it can only swing freely north and south. As the earth turns the pendulum will pull on the gyro unless the gyros axis is parallel to the earths spin. It has to be further damped to keep the axis from precessing in circles. It might be possible to do this damping with friction but as I recall it is done with a little spring that pushes the precessional force slightly off of 90 degrees. The Sperry-Marine history web page gives the name of books that describe this.

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Answer: Brian Turner - 10/05/2004 02:41:12
I found my book. Mechanics by J.P. Den Hartog published by Dover ISBN 0-486-60754-2

The pendulum is limited to north and south not east and west. There is no spring. The pendulum is not directly hung from the gyro. The main trick is how it is hung.

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Answer: braine creeper - 18/11/2012 22:26:51
not sufficient

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