Back setting the minute hand

Discussion in 'Clock Construction' started by dandydude, Sep 14, 2015.

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  1. dandydude

    dandydude Registered User

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    #1 dandydude, Sep 14, 2015
    Last edited: Sep 14, 2015
    Hello,

    I wonder how one could be able to back set (set it anti clockwise) the minute hand. I have built a part of the motion work. I decided to make a rigid clutch spring. By rigid i mean a rubber clutch. I have used a 40 durometer rubber piece. However when i try to back set the minute the movement comes to a stop. It even tries to turn the escapement backwards. Is there something iam missing? I know older clocks couldnt be backset... Any information is appreciated...

    Thanks
    Dandy
     
  2. harold bain

    harold bain Registered User
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    The only reason for not backsetting an older clock is if there is a strike train, damage could be caused by running the train past the activation lever. If you are running a precision regulator, having maintaining power would prevent your problem, as you will have the same problem when winding the clock.
     
  3. dandydude

    dandydude Registered User

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    Dear Harold,

    I never thought maintaining power would solve the problem. I thought even clocks without maintaining power could be set anti clockwise?
    Iam not able to figure out how it works though. When winding the clock the maintaining power compensates for the force in the opposite direction. But with the centre wheel is one level above the great wheel right? Arent you by-passing the power by turning the centre wheel anti clockwise?

    Thanks
    Dandy
     
  4. harold bain

    harold bain Registered User
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    I suppose you are right Dandy. Just checked on a clock I have with maintaining power, and either turning the minute hand backwards, or just putting pressure backwards will stop the second bit. Best advice then would be to always move the hands forward to set the time.
     
  5. dandydude

    dandydude Registered User

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    Dear Harold,

    Was the clock you used a time only regulator? Is it an old clock?

    Thanks
    Dandy
     
  6. harold bain

    harold bain Registered User
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    It is a relatively new tall clock with a Hermle movement, time, strike and chime. I know the maintaining power works as the movement keeps the second bit moving while winding, which is its purpose, so no time is lost while winding.
     
  7. Jim DuBois

    Jim DuBois Registered User
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    A clutch on the motion works of a clock should never be so strong as to stop the mechanism when the hand is moved counter clock wise. If it does, it is too tight or has too high a coefficient of friction, or both. The clutch needs to provide just enough resistance to drive the hands without slippage at all times, but free enough to allow setting back of the hands without stopping the mechanism... some true regulator clocks have no clutch as it is understood that moving the hands either direction even using a properly set up clutch will affect precision timekeeping. Errors are allowed to accumulate and noted in the regulator's log book in such clocks. Most such precision regulator clocks run within fractions of seconds of accuracy, or maybe a second +/- a week so resetting the minute and hours hands is not often required. That approach is perhaps well outside this discussion, but worthy of note.
     
  8. dandydude

    dandydude Registered User

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    Dear Jim,

    I just cant seem to figure how much too tight is. This is the reason iam trying to document how much i compress the spring each time i try turning the minute hand. Iam trying to use rubber as a friction clutch now. I want to try urethane next. I guess its going to take me a lot of trial and error to get the right spec.

    Would it have been a lot more precise if one could use keyless work in a clock? A lot more moving parts, yes, but why not? You could 'not disturb' the movement while setting right?

    Thanks
    Dandy
     
  9. Phil Burman

    Phil Burman Registered User

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    Either the clutch spring is to strong, or the material coefficient of friction is to high, or both. Why not use a material with a lower coefficient of friction, possibly brass? Using this material for a clutch mechanism is quite common I think.

    Phil:)
     

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