Large Pendulum, Mostly Useless/Art

Discussion in 'Clock Construction' started by Greg A, Aug 8, 2018.

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  1. Greg A

    Greg A New Member

    Aug 8, 2018
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    I have an idea for an object I'd like to make, and I'd like to get some clock expert perspective. I'd like to make a large wall mounted pendulum. There wouldn't be a clock, just a large pendulum driven by a mainspring. It would be mostly for art. Ideally, it would utilize large brass gears that are needlessly oversized, for aesthetic purposes. For example, the winding point could be a 1" diamater hex bolt, that you need a huge wrench to turn. Since the pendulum and all the gears would be so beefy, I imagine I'd need a stout mainspring.

    My initial thoughts were really simple. I'm not well versed in gear terms, but I was thinking a coil type main spring on a shaft that has a ratchet type interface with the escapement, so you can add tension to the spring. So, with the escapement wheel on the same shaft as the mainspring, the only other parts would be the anchor-y part that interfaces the escapement teeth, and regulates movement, and the pendulum.

    I think I could be overlooking some huge design flaws. Would this design allow for the safe release or storing of energy if the pendulum is interrupted? If the mainspring is under tension, but the pendulum was at rest, is it possible for the escapement wheel to skip the anchor-y part on the pendulum, and spin out of control releasing all it's energy at once? Would a slightly more involved design with some extra step up/down gears in between the escapement and the main spring be more recommended for controlling energy release and preventing run-away scenarios.

    I'm sure the answer to all these questions is maybe, and it depends. I know this isn't a conventional thing, but I'm just hoping for some extra insight. Any ideas would be appreciated, even though this whole idea is crazy.
     
  2. Phil Burman

    Phil Burman Registered User

    Mar 8, 2014
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    #2 Phil Burman, Aug 8, 2018
    Last edited: Aug 8, 2018
    I think there is a fundamental miss-match in connecting a coil spring directly to a pendulum escapement. A coil spring may rotate something like 5 to 10 revolutions from fully wound to unwound, whereas an escape wheel controlling the beat of a large pendulum will rotate many thousands of revolutions between windings. You will need something similar to a clock movement to convert the high power short travel of the coil spring to the low power long travel of the escapement wheel. You would have the same issue with a weight driven pendulum.

    A small constant torque electric motor directly connected to the escape wheel arbor might be a solution.

    If your main interest is in the aesthetics then a purpose design drive train with oversize wheels and pinions would look pretty good and might be a solution, either spring or weight driven.

    Phil

    PS: Your first paragraph mentions brass gears but you proposed design doesn't include and gears?
     
  3. Greg A

    Greg A New Member

    Aug 8, 2018
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    You're right, I meant gears in the colloquial sense, referring to the escapement wheel and the ratchet wheel; but I had to google those terms, because I don't know the real names for gears. I figured it couldn't be as simple as a one shaft system, but the actual gears of the movement would make it better. I probably can't build such a contraption, but I think I might give it a shot. There isn't a big novelty gear supply store, so I'm not sure how plausible this is anyway. Thanks for your response.

    Also, I've looked into "off the shelf" available large coil style springs, and what I've found that seems the most suitable is a tape measure spring. Would that be outright crazy? Maybe I could stack multiple springs for more power? I'm sorry for all the weird questions. Maybe there is a more suitable spring that I'm unaware of.
     
  4. tom427cid

    tom427cid Registered User
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    Just a thought,use an electric motor (low rpm) to power the escape wheel so that is able to power the verge. Speed is not important because all you are trying to do is establish motion of the pendulum.
    tom
     
  5. Greg A

    Greg A New Member

    Aug 8, 2018
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    An electric motor would probably make the whole thing much easier, but it would mostly negate my purpose, which is a pendulum ran by novelty sized gears, and powered by mechanically stored energy. I've actually got a lot more experience with electrical components, but it just wouldn't be as impressive if a electricity powers the thing. When I say "novelty" sized gears, I just mean the gears are way too big for the intended purpose, like those 10 pound chocolate bars, or a giant comb. In my head I see a pendulum swinging from a large movement that's sandwiched between some exotic hardwood or brass sheeting, and the gears would protrude from the edges, so you can see them in motion. Again, this is all very conceptual right now. Thanks again for the reply

    For a oversized movement like the one I'm proposing, I imagine friction could be a big enemy. I could set all the shafts in ball bearing or bronze bushings. Advisable?
     
  6. novicetimekeeper

    novicetimekeeper Registered User

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    It would be much easier to do with a gravity driven system.
     
  7. Phil Burman

    Phil Burman Registered User

    Mar 8, 2014
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    Again you are describing a clock movement. How long is the pendulum to be and what weight? What kind of size/diameter gears are you thinking of? What duration do you want between windings? What metal working tools do you have available?.

    Frictional losses do not necessarily increase greatly with wheel size. In any case the problem can be solved by the selecting the correct spring.

    Phil
     
  8. Greg A

    Greg A New Member

    Aug 8, 2018
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    Would the mechanism be easier to calculate using a weight because you can more easily calculate the foot pounds of energy being introduced into the system? I would be fine with a weight powered system, since that would include a large weight that descends during operation, making this thing look more interesting.

    It's good to hear that I don't have to worry too much about friction. I've got a full shops worth of regular guy tools, but for precision machining and CNC stuff, I have the best tool of all, cash.

    I'm no where near having a working design, or a prototype, or even a firm grasp on the concepts necessary to accomplish this task. As for dimensions, my rough idea was to mount it to the wall with the mechanism around eye level / 6 foot, and the pendulum would be somewhere in between that and the ground.

    Thanks again for all the insight.
     
  9. Phil Burman

    Phil Burman Registered User

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    This is a good point. As your design is somewhat off piste a degree of experimentation is likely to be necessary. If your selected spring turns out not to be suitable you will need to buy and fit a new spring ..... and so on. If you use a weight driven arrangement and the weight you select is not correct then you just add, or remove, some weight. Once you get the numbers worked out you could switch to a spring drive, in any case I think using the earths' gravity to drive a pendulum is a much more elegant solution that a strip of bent steel.

    Phil
     

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