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  1. #1
    Registered User Scottie-TX's Avatar
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    Default Movement design wheel placement

    I'm considering skeletonizing a Vienna 1 wt. movement. For the purpose of esthetics - sculpting the plates - am also considering moving the third wheel to align with the same vertical center as others.
    Before I move this wheel however, am interested in knowing why the third wheel is ALWAYS off center from the others, and what problems might be encountered if it were on the same center.
    Whaddya tink? Howcum that third wheel is ALWAYS off center and - OH, YES - and always off to the same side of center.
    Attached Thumbnails Attached Thumbnails AWIENER.jpg  

  2. #2
    Forums Administrator harold bain's Avatar
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    Default Re: Movement design wheel placement (RE: Scottie-TX)

    Hope this makes sense. I think it was engineered this way so that the wear of the bushings is AWAY from the next driven gear, instead of into it.
    Or, could be just to make a smaller movement?
    harold bain, Member ch 33
    "If it won't "tick",
    let me "tock" to it"

  3. #3
    Registered User Jeff C's Avatar
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    Default Re: Movement design wheel placement (RE: harold bain)

    I'd say smaller movement which would save on the amount of brass used to produce the plates. Appearance could also play a roll.

  4. #4

    Default Re: Movement design wheel placement (RE: Jeff C)

    They had to calculate the ratio of the wheels to each other. Here's the issue:
    With the existing wheels, the only place they can function is where the circles cross. In order to do what you propose, the entire train has to be recalculated and repositioned. Not impossible, but you might as well just build a new movement
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  5. #5
    Registered User Scottie-TX's Avatar
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    Default Re: Movement design wheel placement (RE: shutterbug)

    If for example, all bushing center spacings are maintained - can the third wheel not be moved upward, to the right, and on center if the EW is moved straight upward on the same vertical center, retaining same bushing spacings?

  6. #6

    Default Re: Movement design wheel placement (RE: Scottie-TX)

    Quote Originally Posted by Scottie-TX View Post
    If for example, all bushing center spacings are maintained - can the third wheel not be moved upward, to the right, and on center if the EW is moved straight upward on the same vertical center, retaining same bushing spacings?
    Can't see why not, if there's room to do it. It would have to be on top of the circle around the bottom pivot, so quite a bit of movement. Lots of skeletal clocks are vertically centered like that. Looks like you could also move the first wheel if you needed the room, and could probably reshape the plates for a cool hour glass look, or similar shape.
    Last edited by shutterbug; 11-09-2009 at 10:21 PM.

  7. #7
    Forums Administrator harold bain's Avatar
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    Default Re: Movement design wheel placement (RE: Scottie-TX)

    No reason it wouldn't work, Scottie. Other movements have been designed with straight line trains. Just needs to be taller
    harold bain, Member ch 33
    "If it won't "tick",
    let me "tock" to it"

  8. #8
    Registered User Scottie-TX's Avatar
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    Default Re: Movement design wheel placement (RE: harold bain)

    OK then; No surprise that we agree it can be done if done properly. We agree all wheels can be on the same vertical center.
    Now: Back to the related question - was this off center design made for reason of efficiency? Reduced cost? Reduced size?
    See, I'm not wanting a skeletonized wiener that requires twelve pounds power!
    Apparently it wasn't a concern between the winding drum and centerwheel.

  9. #9
    Registered User Scottie-TX's Avatar
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    Default Re: Movement design wheel placement (RE: Scottie-TX)

    See, here's another example when I wasn't even hunting one.
    Decided to lean into this little BUCO miniature when first thing struck me was wheel placement! Here, ALL wheels are off a vertical center when I find no space or money saving reason. I gotta believe there is a mechanical reason.
    Attached Thumbnails Attached Thumbnails AWIENER 001.jpg   AWIENER 002.jpg  

  10. #10
    Moderator leeinv66's Avatar
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    Default Re: Movement design wheel placement (RE: Scottie-TX)

    Quote Originally Posted by Scottie-TX View Post
    I gotta believe there is a mechanical reason.
    Yea, I would have to agree Scottie! I've seen plenty of movements where there would be enough room to plant the train vertically, yet they didnít. I have all ways assumed it must have something to do with leverage, but I have never read anything that backs up my thoughts. On the one occasion when I made a movement out of parts, I found it ran easier with an off set train than it did initially when I set it out vertically. I also found that if you moved the off set wheel to the other side of the centre wheel the train would only run smoothly if you turned it anti clockwise. Why? I donít know, but I would like to!
    Cheers
    Peter R Lee: AKA (Pee-Tah) from Australia

  11. #11
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    Default Re: Movement design wheel placement (RE: leeinv66)

    I think that some of you are reading something into this that's more complicated than the real reason.

    You will see that most movements don't put the pivots on a given train in a straight line, and the reason is just to save room, and the amount of brass for the plates.

    It's nothing to do with the mechanical design; that would make no difference at all.

    Some three-train clocks are really bunched together just to allow a smaller case and plates.
    Mike - banned member of the throwaway society.

  12. #12
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    Default Re: Movement design wheel placement (RE: Mike Phelan)

    Scottie, your photo is of a clock with wooden plates. You wouldn't put the train in a straight line with wood plates, unless the grain of the plates ran the opposite way because cutting holes in wood weakens it. You wouldn't want all the holes to be in the same grain line, becasue it would increase the risk of cracking. By the same logic, you wouldn't want the grain horizontal, because the pressures on the wheels tends to push them apart, so the risk of the plate cracking is still there. Therefore, unless the plates are a very closed-grained wood, and fairly thick, relative to the hole diameters, a straight line train isn't practical. Thicker plates means more frictional surface on the pivots, which requires more power, which increases the stresses on the plates, and so on.

    On the other hand, I can think of no good reason for not building a straight line train on brass. I should think it would be relatively easy, if you already have a movement you don't mind changing, to measure the distance between pivots, and, using a compass, to lay them out on a straight line, and drill two straight pieces of brass sheet to construct a vertical - or horizontal - or diagonal straight line tain. The biggest problem that I can think of with a straight line train is there may be some tendency for the brass sheet to buckle, if it is too thin, and all the stresses are in one direction. But if you used fairly thick plates, that shouldn't be an issue.
    Last edited by Dave B; 11-10-2009 at 09:00 AM.

  13. #13
    Forums Administrator harold bain's Avatar
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    Default Re: Movement design wheel placement (RE: Dave B)

    Scottie, here is a straight line designed movement:
    harold bain, Member ch 33
    "If it won't "tick",
    let me "tock" to it"

  14. #14

    Default Re: Movement design wheel placement (RE: harold bain)

    For the other question, I can't imagine a straight line train requiring any more power than an offset one. It would however, as Mike explained, require more room vertically. Conversely, it could be made much narrower, hence the idea of altering the plate shape

  15. #15
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    Default Re: Movement design wheel placement (RE: shutterbug)

    Seems to me the minimum width of a straight line movement would be dictated by the diameter of the largest wheel. That sucker 'uld sure be a long one, if time and strike were all in one line, though.

    Actually, I spose it could be reasonably done, if the time train were mounted above, and you used a one-second pendulum.

    Gee - I wonder if a hammer striking sideways, at about the same position vertically as the pendulum bob, would create sympathetic vibration problems? Where are all those budding young physics graduate students when we need them? Seems like a good subject for a Masters thesis. If the hammer strike were timed such that on one cycle it increased the swing, but decreased it the next cycle, over the course of twelve hours, they would balance out, and the clock would keep time?

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