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  1. #1
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    Default Using just one weight on a two weight Seth Thomas movement

    I am designing a clock to go into a display cabinet for a customer. The movement is a Seth Thomas time and strike weight driven movement from a case that is unusable. I have the original face and suitable hands and the client likes all of that. But, they have asked if I can use just one nice looking brass covered weight that hangs in the middle instead of the usual two lead weights that hang to each side.

    The rough drawing below shows what I am thinking of trying. During a short sequence strike it should not be a problem. But on a high hour count strike I suspect the effective weight on the time side might drop enough to slow or stop the pendulum as the weight falls rapidly to power the strike.

    This could be overcome by using a somewhat heavier weight, but I am concerned with putting too much weight on the movement. I know some of these work fine with as little as 6 pounds each side and most run closer to 8 pounds. Any idea what a safe upper limit might be for the weight on each side of one of these?

    thanks
    Attached Thumbnails Attached Thumbnails OneWeight.jpg  
    The purpose of a discussion is to learn something, not to prove who is right. Dalai Lama

  2. #2
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    Default Re: Using just one weight on a two weight Seth Thomas movement (By: THTanner)

    What is the model of the seth Thomas? I am working on a T&S Seth Thomas 30 hour that has 3 lb on the time and 2.5 lb on the strike.

    David
    David S

  3. #3
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    Default Re: Using just one weight on a two weight Seth Thomas movement (By: David S)

    This is an 8 day Seth Thomas Lyre movement that has 8 pounds for the time and 8 1/2 for the strike. But they are the rectangular lead weights. The display case has glass sides and a mirrored back so they will be able to see the movement and don't really care for the look of the old weights.

    Quote Originally Posted by David S View Post
    What is the model of the seth Thomas? I am working on a T&S Seth Thomas 30 hour that has 3 lb on the time and 2.5 lb on the strike.

    David
    The purpose of a discussion is to learn something, not to prove who is right. Dalai Lama

  4. #4

    Default Re: Using just one weight on a two weight Seth Thomas movement (By: THTanner)

    Sure, but you will need a weight around 16 pounds and you probably won't have enough room (about 3") for a cylinder shaped weight, unless it is very long.
    You will also need around 18 inches of extra case height for an 8-Day runner and the pendulum is going to be way to short for this case length.
    I think the weight cord will pull off the outside of the drums.
    Willie X

  5. #5

    Default Re: Using just one weight on a two weight Seth Thomas movement (By: Willie X)

    I don't understand how you wind it, do you just do equal winds on each greatwheel? I have lots of single weight clocks using the Huygens continuous drive system but the weight drops 5-6 feet in 24 hours.
    Nick, lots to learn, late starter.

  6. #6
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    Default Re: Using just one weight on a two weight Seth Thomas movement

    The plan is to add the little lever that follows the cable as it is wound onto the drum to indicate when each side is full.

    Quote Originally Posted by novicetimekeeper View Post
    I don't understand how you wind it, do you just do equal winds on each greatwheel? I have lots of single weight clocks using the Huygens continuous drive system but the weight drops 5-6 feet in 24 hours.
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  7. #7
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    Default Re: Using just one weight on a two weight Seth Thomas movement (By: Willie X)

    Yes - about 16 pounds. It is a tall, floor display case so the extra height is there. It may look funky though with the 15 inch pendulum which will have to swing between the cables so the weight will not be wound up too close to the movement. I am trying to convince them to use two 8 pounders in brass sleeves hanging on either side as usual.

    Quote Originally Posted by Willie X View Post
    Sure, but you will need a weight around 16 pounds and you probably won't have enough room (about 3") for a cylinder shaped weight, unless it is very long.
    You will also need around 18 inches of extra case height for an 8-Day runner and the pendulum is going to be way to short for this case length.
    I think the weight cord will pull off the outside of the drums.
    Willie X
    The purpose of a discussion is to learn something, not to prove who is right. Dalai Lama

  8. #8

    Default Re: Using just one weight on a two weight Seth Thomas movement (By: THTanner)

    Separate weights will be much less problematic, especially if you have that extra height. It's not that hard to change the escape wheel to one with fewer teeth to get the pendulum length you need.
    Willie X

  9. #9
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    Default Re: Using just one weight on a two weight Seth Thomas movement (By: Willie X)

    It is a fun project, but getting out of hand. It is a lighted case with glass shelves and mirrors. Either way I go the glass shelves will need to be cut for the weights and pendulum. I think I have that figured. But, they also want me to put a mirror on the back of the face so that the front of the movement is reflected in the mirror at the back of the case. Sadly their clock went through a fire and the veneer was totally ruined and the glass broken during the fire fight. Their rebuild is a lot more modern than the original interior and they love the clock. Soooooo, we proceed.

    Quote Originally Posted by Willie X View Post
    Separate weights will be much less problematic, especially if you have that extra height. It's not that hard to change the escape wheel to one with fewer teeth to get the pendulum length you need.
    Willie X
    The purpose of a discussion is to learn something, not to prove who is right. Dalai Lama

  10. #10
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    Default Re: Using just one weight on a two weight Seth Thomas movement

    This is a picture of the display case. The top glass shelf will become a seat board of sorts with holes and cut outs and a brass mounting U shaped plate for the movement with knurled through bolts and nuts. A rather sad change of life for a Lyre.
    Attached Thumbnails Attached Thumbnails IMG_2887.JPG   IMG_2888.JPG   IMG_2889.JPG  
    The purpose of a discussion is to learn something, not to prove who is right. Dalai Lama

  11. #11

    Default Re: Using just one weight on a two weight Seth Thomas movement (By: THTanner)

    Would be best if the cables were parallel. If you are going to modify the movement for a long pendulum, perhaps you can modify the bottom of both trains to drive from a single main wheel and spool?

    RC

  12. #12
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    Default Re: Using just one weight on a two weight Seth Thomas movement (By: R. Croswell)

    Perhaps - but I am hoping to keep the movement as original as possible and modify the case to make it work and appear pleasing. Since the cables come off the outside of the drum if they go down instead of up to the top pulley, I am thinking I can use a little less weight since there should be less friction loss. The movement goes onto a mock up seat board later this week for testing some ideas. Right now I am planning to leave the pendulum and EW alone, but that might change.

    Quote Originally Posted by R. Croswell View Post
    Would be best if the cables were parallel. If you are going to modify the movement for a long pendulum, perhaps you can modify the bottom of both trains to drive from a single main wheel and spool?

    RC
    The purpose of a discussion is to learn something, not to prove who is right. Dalai Lama

  13. #13
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    Default Re: Using just one weight on a two weight Seth Thomas movement (By: THTanner)

    It is also possible that they do not understand the difference between
    the weights and the pendulum. We have seen that confusion quite
    often on the MB.
    If you go with the single weight, the Geneva stops should be enough.
    ( assuming it still has them ).
    Tinker Dwight

  14. #14
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    Default Re: Using just one weight on a two weight Seth Thomas movement (By: Tinker Dwight)

    No Geneva stops on this weight movement. I suppose I could conjure one up, but I rather like the lever that tracks the cable instead.

    Quote Originally Posted by Tinker Dwight View Post
    It is also possible that they do not understand the difference between
    the weights and the pendulum. We have seen that confusion quite
    often on the MB.
    If you go with the single weight, the Geneva stops should be enough.
    ( assuming it still has them ).
    Tinker Dwight
    The purpose of a discussion is to learn something, not to prove who is right. Dalai Lama

  15. #15

    Default Re: Using just one weight on a two weight Seth Thomas movement (By: THTanner)

    Quote Originally Posted by THTanner View Post
    No Geneva stops on this weight movement. I suppose I could conjure one up, but I rather like the lever that tracks the cable instead.
    Or simply attach (crimp on) some sort of brass sleeve or little ball that would contact the seat board when that spool is full. You may have issues with driving force when the weights are at the top and angle between the cables is large. If the cables were directed over pulleys under the seat board such that they were parallel you will have more constant power over the run cycle that will be a greater advantage than any thing gained from not having the friction of the pulleys.

    RC

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