Mystery Clock Suspension.

Discussion in 'Clock Construction' started by Drummerboy, Jul 12, 2016.

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  1. Drummerboy

    Drummerboy New Member

    Jul 20, 2014
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    Hi All
    my first post (and my first clock) so please go easy.
    I am making a mystery wall clock.
    basically a seconds pendulum (swinging on the wall with no visible means of impulse) but with the clock movement and dial as the bob.
    Breguet did it with a Mechanical movement but I can't do that so I am using a quartz insert movement driven by a coil, magnetic repulsion and bbc micro bit.

    For simplicity I am reversing the usual arrangement of coil under the pendulum and magnet on the rating nut, so I need my pendulum to swing fixed in one plane. The coil will be behind the bob and the magnet hidden in the backboard.
    My question is - can I replace the usual pendulum suspension spring with a ball race or will the friction be too great? I think the magnetic repulsion will cause a suspension spring to wobble as it will be pushing it away from the wall.
    thanks for any help and advice.

    Kester Sims
     
  2. Allan Wolff

    Allan Wolff Moderator
    NAWCC Member

    Mar 17, 2005
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    Tulsa, OK
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    I think a ball bearing would work fine. Probably run it dry so the oil does not add friction as it dries over the years. Get a good quality bearing; ABEC 5 or better. Some of the cheaper bearings seem to be rough or have a lot of slop.
     
  3. tok-tokkie

    tok-tokkie Registered User

    Nov 25, 2010
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    If you do go for a bearing then conventional chrome steel bearings are the cheapest. However it is best to remove all the grease as that makes them rotate MUCH more freely. To keep dust out of the bearing it is best to use shielded bearings. I have degreased many bearings and the best way is put them in neat engine degreaser then flush them in running water. Repeat a few times. I left them overnight.
    The problem is the bearing is then liable to get surface rust. So instead use stainless steel ball bearings. Better still is stainless steel races with ceramic balls. Top of the class is pure ceramic bearings (races and balls). Boca bearings is an excellent source for small bearings.
    Note that bearings are not recommended for small angle oscillating movement. I have the pallets on the clock I have made running in stainless ball bearings without any issues as yet and they oscillate just a few degrees.
     
  4. Tinker Dwight

    Tinker Dwight Registered User

    Oct 11, 2010
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    Calif. USA
    How about a second pendulum behind the backboard
    that is loosely coupled at the suspension to drive the front
    one with sympathetic oscillation.
    It can be a compound pendulum to make it shorter.
    Another thought is to have the sense coil behind the board
    but drive the pendulum with a coil above or near the suspension.
    Tinker Dwight
     
  5. Drummerboy

    Drummerboy New Member

    Jul 20, 2014
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    I really like the idea of a second pendulum...
    It wont work behind my backboard as it is hanging on a wall.

    So now I am picturing a four glass mantel clock with a piece of decent polished wood dividing the middle, two 1/2 second pendulums hanging either side of the wood from the same suspension, drive pendulum on the back with coil and magnet in more traditional place, the sympathetic pendulum on front with the Quartz mvmt as the pendulum bob.
    The first problem that springs to mind is how to get the wires from the electronics under the drive pendulum to the bob of the display pendulum.
    this may be my second clock!
    thanks Tinker

    Kester Sims
     

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