Welcome to the NavList Message Boards.


A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Add Images & Files
    Re: Gyro sextant
    From: David Pike
    Date: 2019 Jan 31, 02:39 -0800

    Bill.  I’ve tidied up my original explanation.  This is my final attempt (well, until my gyros arrive from eBay)

    If the nominally vertical spin axis of the spinning gyro is displaced out of the vertical for any reason, gravity doesn’t cause the gyro to topple further or swing back into the vertical as might be expected from either a top heavy or bottom heavy gyro.  Instead, the gyro precesses like a child’s top such that its spin axis follows a path akin to moving around the outer surface of a cone with the apex of the cone coinciding with pivot point of the gyro. This conical movement awakens fresh forces upon the gyro.  Typically, the pivot point will attempt to follow a circular path of small radius within its cup, as opposed to the zero radius of a gyro with a perfectly vertical spin axis.  Therefore, there will be a tiny frictional force in the opposite direction to the one in which the pivot point is trying to walk.  This is akin to pulling at the bottom of the spin axis, and due to the same process which causes a spinning gyro to precess when disturbed from the vertical, will cause the gyro to gradually re-erect itself. 

    Put more simply, vertical force, gravity, can only cause a spinning top to precess in the horizontal plane.  For the gyro to precess in the vertical plane, you need to apply a force which is both in the horizontal plane and in the correct direction, e.g. friction at the pivot point due its attempt to travel around a tiny circle inside its cup. DaveP

    Browse Files

    Drop Files


    What is NavList?

    Join NavList

    (please, no nicknames or handles)
    Do you want to receive all group messages by email?
    Yes No

    You can also join by posting. Your first on-topic post automatically makes you a member.

    Posting Code

    Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.

    Email Settings

    Posting Code:

    Custom Index

    Start date: (yyyymm dd)
    End date: (yyyymm dd)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site