Terry Style Verge Project

Discussion in 'Wood Movement Clocks' started by gleber, Mar 25, 2016.

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  1. gleber

    gleber Registered User

    Jun 15, 2015
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    I just finished a gear repair and reassembly of a Terry Style movement. The next step to get it running is to replace the verge that was missing when I got the clock. The escape wheel has 32 teeth and is about 1.3" diameter.

    Here is my movement:
    20160325_100738.jpg

    And here is a photo of a Terry movement I took at Merritt's.

    20160311_133708.jpg

    It also has a 32 tooth escape wheel and it looks like the verge spans 7-1/2 teeth. I have three questions.

    1. Is spanning 7-1/2 teeth correct for a 32 teeth escape wheel?
    2. Are the angles of the pallet cuts correct - entry on the cut, exit on the reverse of the cut?
    3. It looks like the length of the crutch is to the bottom pillar. Is this correct?

    Thanks,
    Tom
     
  2. Tinker Dwight

    Tinker Dwight Registered User

    Oct 11, 2010
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    #2 Tinker Dwight, Mar 25, 2016
    Last edited: Mar 25, 2016
    Optimum adjustment is when the lock surfaced are at a tangent
    angle of 45 degrees. A straight line across the face should be
    at the same distance to the arbor when the tooth is about to
    drop off the pallet. Start with a drawing of the escapement wheel.
    Draw lines to show the angle with each one crossing the wheel
    at a tip and half way, with one to be the exit, at a tip, the other should be
    45+ the amount of swing expected. ( 5-8 degrees? )
    This would be such that that tangent line was higher, away from the
    arbor, not closer. The entrance surface should be real close to
    the tip of the next tooth but the end of the pallet should be slightly
    longer than to a center span.
    The span should be about 1/4 the circumference, as it is in the picture.
    Start out with a slightly longer entrance pallet as the only way to
    adjust the entrance drop would otherwise require changing the angle
    of the exit pallet. ( for fine tune OK but not for main adjustment )
    Constantly check the depth. If you over trim the length of the entrance pallet,
    you'd need to start over. Exit drop is set by the depth.
    Tinker Dwight

    PS please excuse any typos. I broke my wrist last weekend so that now
    my two fingered typing has been reduced to one finger.
     
  3. gleber

    gleber Registered User

    Jun 15, 2015
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    Ouch! Sorry to hear about your wrist. Hopefully it won't affect your clockworking ability and you won't be laid up too long.

    That is quite a mouthful. I've read it at least 3 times and I'm still having a hard time picturing it all, but I think I have the gist of the key points. I also found this: http://www.nawcc-index.net/Articles/Headrick-EscMechanics.pdf, which I think explains the concepts including the 45 degree logic and has some nice diagrams.

    If you have any pictures or other references, I would appreciate them.

    Thanks,
    Tom
     
  4. Tinker Dwight

    Tinker Dwight Registered User

    Oct 11, 2010
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    There are a number of books that show this but few
    go into the details of fitting the pallets.
    Buy a couple of blank pallets.
    It is always best to make drawings. You can then make
    paper cutouts and use pins for arbors. It is easier to
    play with paper, pencil and scissors than bending and grinding
    metal.
    Recoils are quite forgiving. The trickiest part is getting the
    entrance drop right, since that can only be adjusted by
    the length of the entrance pallet or a tiny change in the
    angle of the exit.
    Once drawn, you can bend the pallet and have it close to
    right. Remember you can't cut it longer, only shorter.
    Tinker Dwight
     

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