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The Mechanics of a Gyroscope

written by: Ashwin Satyanarayana • edited by: Swagatam • updated: 9/2/2008

Do you know what a Gyroscope is? Do you know the Principle of Precession? A gyroscope Literally defies gravity and is based on the principles of Angular Momentum and this article just tells you how it works.

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    The gyroscope is probably the only perplexing device made by man which defies the law of gravity!

    A conventional gyroscope is a mechanism comprising of a rotor made to spin about one axis, the journals (screws) of the rotor being mounted in an inner gimbal (ring), and the inner gimbal being fixed for oscillation into an outer gimbal which is in turn fixed for oscillation to a relative support. The outer gimbal or ring is mounted so as to turn about an axis in its own plane determined by the support.

    The gyroscope is a spinning wheel or disk whose axle is free to take any orientation/direction. This direction changes much less in response to a known external torque than it would without the large angular momentum associated with the gyroscope's high rate of spin. Since external force is minimized by mounting the device in gimbals, its orientation remains nearly fixed, regardless of any motion of the platform on which it is mounted.

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    A Gyroscope

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    This device is used for measuring or maintaining orientation, based on the principles of angular momentum.

    The axle of the spinning wheel defines the spin axis. The inner gimbal possesses a rotation freedom of two degrees and its axis possesses one degree of rotation freedom. The rotor is made to spin about an axis which is always perpendicular to the axis of the inner gimbal. So, the rotor possesses three degrees of rotational freedom and its axis has two degrees.

    The special properties of a gyroscope are extremely important and are used in an assorted number of other instruments ranging from a normal bicycle to the advanced navigation of a space shuttle.

    The ability of a gyroscope to defy gravity is baffling!

    The special property of a gyroscope that defies gravity is called as precession. Precession refers to the ability of the gyroscope to resist motion about the spin axis.

    This can be observed when the bicycle wheel is made to hang with a string tied to the axle of the wheel as shown below:

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    Bicycle Wheel

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    And by spinning the wheel, the most amazing thing happens which can be watched in the following video link provided at the end of this article.

    This odd behavior displayed by the bicycle wheel appears very irrational which makes us think the logic behind the axle of the bicycle hanging in mid-air like that. The same logic is applicable to the gyroscope which when supported loosely at one end would describe a circular motion, instead of just falling under the influence of gravity.

    The logic of precession can also be observed in a spinning top. Once the sting of the top is let loose, the top instead of falling, as might be expected, appears to defy gravity by remaining with its axis horizontal, when the other end of the axis is left unsupported and the free end of the axis slowly describes a circle in a horizontal plane, the resulting precession turning.

    Another distinguished property of the gyroscope is called as nutation. Nutation is a minor irregular motion (etymologically a "nodding") in the axis of rotation of a largely axially symmetric object, such as a gyroscope or a planet. It is this property of the nutation that gives a slight wobble to the spinning object.

    These distinctive properties of a gyroscope make it a very unique and puzzling object. The simple gyroscopic properties are made use in aircrafts and space shuttle for navigation purpose.

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    Videos and Further Reading

    Watch Video Here

    Other Content You could Read

    HowStuffWorks -- How GyroScope Works