Size and number of teeth on gears

Discussion in 'Clock Repair' started by JayRs, Mar 25, 2014.

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  1. JayRs

    JayRs Registered User

    Mar 17, 2014
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    I need to dissemble a Seth Thomas 89c to replace a broken mainspring. I've study and photographed the movement, but to make sure to make sure I understand the operation of all the components and document their placement I want to make a 3d model (another hobby of mine) of the complete movement before I proceed. Being the somewhat anal person I am, I want to make the model as accurate as possible so I'm looking to find a list of the size and number of teeth on each gear. Does such information exist?
    Thanks, Jay
     
  2. shimmystep

    shimmystep Registered User

    Mar 5, 2012
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    I know not of such a list, however I am intrigued by your thoughts of making 3d model of the movement, can you explain in more detail, materials, detail, methods etc etc, have you an e.g/picture of another?
     
  3. JayRs

    JayRs Registered User

    Mar 17, 2014
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    It is not a physical model, but a virtual model done with a computer which can be animated. I did something similar for a steam locomotive I was interested in.
     
  4. eskmill

    eskmill Registered User
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    Aug 24, 2000
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    I do not believe such a list exists. Obviously, such specifications and drawings did exist within the Seth Thomas engineering department but it was over a hundred years ago. Too the 89 movement underwent many versions and improvements over several generations.

    Consider too, that the Seth Thomas company has been sold at least twice in the past 40 years or longer and at the last sale, all records were said to be destroyed. Fortunately, the records of all Tower clocks was preserved by diligent members of NAWCC.

    My advice is to seek a "junker" model 89 movement for your project....disassemble it and count the teeth....that's what our "Cog Counter" members do.

    Yours is a formidible undertaking and I would advise you to attach your signature to all your drawings.

    Many years ago, R. E. Swan created accurate drawings of many, many American made spring driven clock movements and published a book with the drawins. Fortunately for Swan, his work is copyright and is used only for reference.
     
  5. Jay Fortner

    Jay Fortner Registered User

    Feb 5, 2011
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    Take the movement you've got,let the power down and use a fine line sharpie and mark each wheel at every fifth tooth then count them all up. When you disassemble the movement just wipe away the ink marks with acetone or carb cleaner. Sounds like you're a mechanical engineer so you know to get diameter multiply radius times two. You can get the radius with a set of dividers. Once you get the tooth count you can multiply it by the module and get the circumference then divide by pi for the dia.
     
  6. Willie X

    Willie X Registered User

    Feb 9, 2008
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    JayR,

    I can save you a lot of trouble!

    After you completely let down the springs into a clamp or wire, carefully remove the back plate and then pick out each wheel (top to bottom) and stick each wheel into a large block of Styrofoam. Keep the wheels oriented in the way you pulled them out and there can be no problem putting them back where they came from.

    Actually you are worrying about something that is rarely a problem. The wheels (with rare exception) will only go back in the right position ...

    Good luck, Willie X
     
  7. David S

    David S Registered User
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    Dec 18, 2011
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    Hi Willie i think you may not have comprehended Jay's post. He wants to make a computer 3D model as I understand it.
     
  8. JayRs

    JayRs Registered User

    Mar 17, 2014
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    David, that is right, but only as a precursor to working on the actual movement so I can be sure I fully understand it's working and minimize my mistakes on the real thing.
     
  9. harold bain

    harold bain Registered User
    NAWCC Member Deceased

    Nov 4, 2002
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    Spend more time studying your movement, until you understand what each part does. Make notes, and take pictures as you take it apart.
     
  10. Tinker Dwight

    Tinker Dwight Registered User

    Oct 11, 2010
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    The actual modulus of the wheel is from a diameter slightly
    less than the tips of the teeth.
    Once you have the number of teeth, you can measure the distance
    between arbors.
    The ratio of the teeth is the same as the ratio of the modulus
    radius calculation.
    As an example, say the wheel was 42 teeth and the pinion was
    8 teeth.
    Now say the distance between the arbors was 2 inches.
    2/(42+8)= x/42
    solving for x=1.68 inches, the radius of the 42 toothed wheel,
    for modulus calculation.
    Tinker Dwight
     
  11. Willie X

    Willie X Registered User

    Feb 9, 2008
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    Yes I "comprehended" what was written. Trying to figure out the why, the unwritten part. Ha

    Willie X
     

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