Differences in long vs short drop wood movements?

Discussion in 'Wood Movement Clocks' started by spxer, Nov 26, 2019.

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  1. spxer

    spxer Registered User

    Jun 20, 2016
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    What are the differences in long or regular length pendulum wooden movements and the shorter wooden clock movements? Obviously the escape wheel tooth count and verge. Generally 32 vs 42 teeth on those I have seen. Are there other differences in the gear train or cable barrel etc? Can they be interchanged by substituting a different escape wheel?
     
  2. salvtrinny

    salvtrinny Registered User
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    Sep 13, 2012
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    In the short drop wood movements, the winding barrels are smaller in diameter. The escape wheel has more teeth as you mentioned. I'm not sure of the tooth count of the gears. The access holes (4) are smaller and early short drops have a squared hour hand mounting hole.
     
  3. spxer

    spxer Registered User

    Jun 20, 2016
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    Thanks for the info. I am getting educated!
     
  4. jboger

    jboger Registered User

    Jan 7, 2019
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    I'm going to go out on a limb with the hope that someone will correct my error. It's been along time since I actually looked at this. Here goes. One can calculate the number of beats per hour (or length of pendulum) by taking a ratio of the number of wheel teeth to pinion leaves. (I believe the equation has a number of terms in it, one for each wheel/pinion combination. This equation can be looked up.) I suspect the shorter the length of the pendulum, the greater the number of beats per hour. Or simply put, the clock beats faster than a clock with a longer pendulum, all other things being equal. You could probably interchange the escape wheels between the two clocks and have them run, but probably one of the cases couldn't accommodate the longer pendulum that would be required. What would be the motivation for having long- and short-pendulum clocks? Overall size would be one consideration. Probably another would be that the long pendulum (i.e.slow beat) clock would experience less wear and have a longer shelf life. I'll leave it at that. Perhaps my post will induce someone to be more quantitative than I.
     
  5. R. Croswell

    R. Croswell Registered User

    Apr 4, 2006
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    The only short drop for which I have records (Terry), ratios are:
    Esc 42/8 32/8 36/8 ctr 40

    A couple long drops ( Riley and Barns), the ratios are::
    Esc 32/8 32/8 36/8 ctr 40

    I have one long drop with 42 tooth center wheel.

    So yes, changing the escape wheel would from 42 to 32 would allow the clock to run a longer pendulum, but the time keeping ratios are from the center wheel to the escape wheel, As I believe has already been mentioned, the lower train and spool diameter determine if the weight drop will be long or short. Simple physics says the amount of weight that drops a given distance is the energy given to the clock. If you shorten the weight drop you will need a slightly heavier weight for the same amount of energy transfer. Over the universe of American wooden movements there may be some that short drops that differ from long drops in more than the number of EW teeth and spool diameter.

    RC
     

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