Poising for zero G - a speculative thread

Discussion in 'Watch Repair' started by karlmansson, Jul 13, 2019.

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  1. karlmansson

    karlmansson Registered User

    Apr 20, 2013
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    Hello!

    I’ve been seeing the George Daniels Space Traveler pocket watch, possibly due to the upcoming 50th anniversary of the moon landing. The latest one was an edited image of an astronaut in space “holding” the watch. It made me think.

    Apart from the extreme changes in temperature (that I’m very doubtful that the pocket watch could handle, see the Omega Project Alaska for an insight into what it would take to handle the shifts), how would you poise a watch for zero G? I assume that the actual moon landing Omega Speedmasters were adjusted in this way.

    Everything we do in dynamic poising is related to gravitational effects on the balance assembly. Would you treat the adjustment of a watch designed to work in zero G as a you would a tourbillion watch? Put it on a winder and see how it keeps time after a day or so?

    As the title implies, this is not a very practical discussion. I just though it would be interesting to consider. Plus, it might give some insight into what havoc, or possibly benefits, we get from the influence of gravity on various parts of a mechanical watch.

    Best regards
    Karl
     
  2. GeneJockey

    GeneJockey Registered User
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    Dynamic poising is really just ensuring that the balance is as close to perfectly mass balanced at every point, because without that, the force of gravity will pull more on the heavier side than the light side. Theoretically, the effect of lack of mass balance on the variation in rate will be directly proportional to the force of gravity. Thus at 2g, poising would be even more important than at 1g, while at 0g, it would be much less important, I think.

    But one thing about gravity on Earth is the direction of the force is pretty much constant. DU and DD, the balance pivots sit on endstones and have very low friction. Pendant positions, the two pivots sit on the side of the pivot holes, and have somewhat more friction, and thus a lower amplitude. At 0g, there's no constant direction of force, so where the balance pivots would be constantly changing, right?

    Mind you, I'm a Biologist, not a Physicist, so this is all handwaving.
     
  3. karlmansson

    karlmansson Registered User

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    And I’m a medical doctor so I feel like we’re in the same boat here, more or less :).

    I dont completely agree with your description of dynamic poising. I think what you are describing is static poising. Dynamic poising will produce a balance wheel with an uneven distribution of mass. The reason being that unevenness will compensate for other imperfections in the balance assembly such as long and short arcs of the hairspring.

    Maybe the answer is simply that you need a perfectly statically poised balance? I would imagine that vibration might become an issue as well. Without gravity keeping at least on part of the balance wheel in firm contact with the jewels the end and side shake might be enough to create a chatter of sorts?

    Thanks for contributing!

    Karl
     
  4. GeneJockey

    GeneJockey Registered User
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    No, really I'm talking about dynamic poise, because static poise ignores the hairspring and all of its mass and where that mass lies, and how the effect changes as the hairspring winds up and down. Dynamic poise still deals with the effect of gravity on mass distribution in the balance. Obviously there are other factors as well, but I'd think a movement that's as close to perfectly poised dynamically would perform better no matter the local gravity.
     
  5. karlmansson

    karlmansson Registered User

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    Well, yes and no. We are certainly dealing with altering the center of mass but the term “dynamic” implies taking other forces into account as well. Dynamic poise demands gravity to be done so a “perfect dynamic poise no matter the local gravity” doesn’t really exist as far as my reasoning takes me. If you poise a balance at 1G that poise won’t be valid at 0G.

    You are taking the weight of the hairspring into account in dynamic poising but also the differences in forces between winding and unwinding the hairspring and positional variations of an non-counterbalanced levers.

    Regards
    Karl
     
  6. GeneJockey

    GeneJockey Registered User
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    True, but I'm thinking that zeroing out positional error, so the rate is constant no matter the direction of gravity, should also work when gravity is zero.

    Did Omega do more than that to the balances on the Speedmaster Pro? They had to work equally well in zero G, 1G, and however many Gs were encountered during liftoff and reentry.
     
  7. karlmansson

    karlmansson Registered User

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    I dont know about the Speedmasters, it would be interesting to know.

    I’m not convinced that they would work equally well in zero G. When we are dynamically poising we are adjusting the gravitational effects IN RELATION to other forces and factors. Adjusting the mass distribution of the balance is the most approachable and predictable way to make the adjustments so that is what we do. But adjusting to six positions is only viable if those positions can be oriented to a gravitational field. A watch that is dynamically poised should become out of poise when the one force that is compensated for is no longer a factor. Then inertia and acceleration of the whole assembly will come into play.
     
  8. GeneJockey

    GeneJockey Registered User
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    I guess the unanswered question is how much of dynamic poising is about the changing mass balance due to the hairspring and collet and the fact that the former is fixed at one end, and how much is about other factors within the movement. That is, some percentage of dynamic poising has to do with mass balance in the balance/hairspring assembly, and some percentage has to do with other factors. But how much of each is it? That's the unknown.

    The thing is, it's a zeroing out of errors in ALL orientations. It's not making the watch accurate in one orientation at the expense of the others.
     
  9. D.th.munroe

    D.th.munroe Registered User

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    These guys may have found out.
     
  10. Ticktinker

    Ticktinker Registered User
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    #10 Ticktinker, Jul 15, 2019
    Last edited: Jul 15, 2019
    This made me interested in the G factors,
    I found by a search the astronauts experienced 4 G's force in lift off, just prior to engine cut off...
    And then 7 G's upon earth re-entry.
    I have to wonder how the watches ran after the two events in the mission.
     
  11. karlmansson

    karlmansson Registered User

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    Well, that was a teaser... :). That’s exactly the sort of experiment I was hoping someone had done!
     

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