Gearing effects on mainspring

Discussion in 'Clock Repair' started by ChrisCam, Feb 12, 2018.

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  1. ChrisCam

    ChrisCam Registered User

    Dec 9, 2017
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    Hi, as we all know gearing reduces / increases the power transmitted to each wheel proportional to the size of each wheel (number of teeth). Therefore at the upper end of the train (furthest from the spring) if these gears are forced can they exert enough force down the train to act on the spring to break it. I ask because I had a main spring go shortly after turn a star wheel on its pinion to give more slack to the hammer tail. Possibly I inadvertently forced the gear train is this likely or was it just coincidence the strike train spring broke?

    regards
    CC
     
  2. wow

    wow Registered User
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    Chris, I don't think it is possible to exert that much force from the upper gears. Just coincidence. Is what I think.
     
  3. ChrisCam

    ChrisCam Registered User

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    Yes think your probably right as a slight turn on the star wheel (or its associated pinion) would only produce a fractional movement on the main train wheel? But boy when these springs go...they go!

    Regards CC
     
  4. Willie X

    Willie X Registered User

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    I would answer your question with a 'yes'. But, I can't imagine any normal condition that would result in breakage. You would have to have the spring wound up tight and really force the wheel you mention backwards quite a bit, probably around 1/2 turn on the 3rd wheel.
    Willie X
     
  5. ChrisCam

    ChrisCam Registered User

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    Yes that's what I thought so probably a coincidence.
    CC
     
  6. wow

    wow Registered User
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    Willie, don’t you think teeth would strip, pinions would break, or arbors would bend before there would be enough power to break a mainspring?
     
  7. ChrisCam

    ChrisCam Registered User

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    If it helps.....About 5 or ten mins after I did a tiny adjustment on the star wheel there was an almighty whining and yes a couple of pinions bent one wheel went flying across the bench and I guessed the spring had broken and yes indeed it had (no resistance on winder). Is it usual for wheels to be stripped when a spring goes?

    Regards
    CC
     
  8. Willie X

    Willie X Registered User

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    Maybe you broke a trundle in the pinion, or broke off a tooth when moving that star wheel. That would be more likely that exerting enough force to break the spring. This would also explain the delay and the loud whining noise. Your spring may have survived the mishap undamaged. Willie X
     
  9. ChrisCam

    ChrisCam Registered User

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    Sherlock Holmes A.K.A Willie is right just double ckecked, spring is indeed intact. Moral of story be careful trying to shift star wheel in future, partial disassembly better route than trying to turn star wheel by leverage even a little could be disastrous.

    Regards
    CC
     
  10. shutterbug

    shutterbug Super Moderator
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    Yeah, you don't want to exert too much pressure on small pivots. Some counter force is also needed.
     
  11. ChrisCam

    ChrisCam Registered User

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    Thanks shutterbug, have sucsessfully shifted 2 other star wheels this one was not going anywhere I tried to hold pinion with pliers but fear I must have lost the battle. Do you more experienced guys try to move a starwheel if there is not enough slack? My guess is yes but if in any doubt you partially disassemble:???:

    Regards CC
     
  12. kinsler33

    kinsler33 Registered User

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    I guess it depends on the age and type of clock. On the average Hermle grandfather movement you can usually brace a wooden punch--that is, a stick--against one of the star wheel teeth and give the other end of the stick a good clop with a screwdriver handle to turn the star wheel a bit. A more cautious approach would be to clamp a pair of long-nose Vice-Grip locking pliers onto the star-wheel arbor prior to this sort of insult.

    It sounds like it might indeed have been an old clock with elderly lantern pinions. I believe Mr Shutterbug and others here have designed special pin wrenches that will turn a star-wheel far more gently, and if I wasn't so lazy I'd have made one or two by now.

    I've been lucky enough thus far that disassembly hasn't generally been necessary, though on some clocks that star wheel simply doesn't rotate.

    M Kinsler
     
  13. ChrisCam

    ChrisCam Registered User

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    Thanks Kinsler, very helpful, Shutterbug good kind Sir can you suggest anything:???:

    Regards
    CC
     
  14. David S

    David S Registered User
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    All of the star wheels I tried to adjust took way too much force for my liking so made a couple of crude wrenches, one hooks into the star wheel the second grabs the crossings of the wheel so all the reaction forces stay local.

    star wheel adjusting wrenches.jpg

    David
     
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  15. wow

    wow Registered User
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    Great idea, David. Gonna make me a set. Thanks.
     
  16. Jay Fortner

    Jay Fortner Registered User
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    Get the timing right during assembly and you don't have to move,twist,bend and break stuff.
     
  17. ChrisCam

    ChrisCam Registered User

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    Thanks David took 5 minutes to see exactly what you mean. Yes a great idea so will make some. It certainly reduces risk but always a chance if to much force was applied now I have broken one I will endeavor to be more careful.
    Regards CC
     
  18. ChrisCam

    ChrisCam Registered User

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    Thanks Jay without doubt you are right can you run through or point me in the direction of reassembly to get it right. Baring in mind at assembly the train has no power to it is it in practice possible to get it spot on and if not would you go for a partial disassembly or the leverage method. There are obvious concerns if its a customers valuable or sentimental clock. I would tend towards try gently using the spanners David suggests otherwise disassembly.

    Regards
    CC
     
  19. Jay Fortner

    Jay Fortner Registered User
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    It varies by design. On most German clocks the first thing to time is the star wheel and hammer lever. Set the timing on that where the lever is just falling off the tip of the star point. The next point up the train is the gathering pallet. On some clocks the train is locked by the gathering pallet,others lower a locking lever to arrest the train. When the hammer drops,set the locking point of the GP. The final timing point is the warning wheel. With the train locked the warning pin on the wheel should be 90-180deg. advanced of the warning lever.
    Always run the train manually to check timing before applying power and if it's not right take it apart and do it again.

    Like I said,designs vary. It's best to slowly run the train using finger pressure on the mainwheel before disassembly and note where the hammer drops and where wheels and and pins come to rest. Make mental notes or take clear pics of those three areas.

    Remember,the clock was timed when you took it apart,it can be timed again without bending and twisting.


    Once everything works like it is supposed to you can oil it up and your good to go.
     
  20. shutterbug

    shutterbug Super Moderator
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    Quite often the star wheel position can be controlled at the gathering pallet. When I have to move the star wheel, I use the sharp tap method rather than a steady pressure. It seems to move things easier :) The newer German made clocks are less prone to issues because the friction fit is not so tight.
     
  21. ChrisCam

    ChrisCam Registered User

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    Thanks Jay and Shutterbug, I will note and apply your comments.

    Regards
    CC
     
  22. Jay Fortner

    Jay Fortner Registered User
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    Tapping has the same effect as a mainspring blowing,sudden shock load.

    I'm sure this mans clock is now destroyed because he read here on the MB that the star wheel could be rotated after the movement is assembled and in some clocks this is true. Not the case this time.

    Well done guys!
     
  23. shutterbug

    shutterbug Super Moderator
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    Well Jay, it's been used hundreds of times successfully. This one is the only exception I can remember.
     
  24. kinsler33

    kinsler33 Registered User

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    It's generally fairly obvious when the star wheel has been assembled such that it'll allow rotation on its shaft because the star-wheel will be mounted on a sleeve that's a press fit on the arbor.

    The few clocks I've seen that do not allow external strike timing have been round-movement time/strike models that flip the hammer with a pin-wheel rather than a star-wheel. Just about everything else I've seen either allows ex post facto strike timing or is engineered so that the timing will always be correct when it's assembled. I don't think I've ever seen a chime clock in which the chimes couldn't be post-adjusted, either.

    If you're at all concerned, however, it's not a huge deal to let down all mainsprings and with the use of a plate-spreader tool to un-mesh whichever strike wheels are handiest to get to and then turn the star wheel where it's supposed to be.

    As to the position of the gathering pallet affecting the strike timing, I always hope it will help but it seldom does because of the gear ratios in a clock whose gathering pallet has but a single pin. However, the Korean clock I just did--the one that was sent by Kim Jung Un to destroy the west and teach me more clock repair--has a three-pin gathering pallet, and this one's strike timing is affected in interesting ways when you adjust said gathering pallet. (I learned a lot from that clock: always bush the gathering pallet arbor so the g.p. doesn't dig too far into that little tin rack and make sure that the g.p. isn't rotating on its shaft when you aren't looking.)

    When you've got the clock in question apart next, carefully clamp the star-wheel arbor in a vise and see if the star wheel rotates on its arbor. It'll be a tight but moveable friction fit.

    Mark Kinsler

    It's apparently fighting season here in the Forest of Brass. Sheesh.
     
  25. ChrisCam

    ChrisCam Registered User

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    Thanks Jay, If any of you have experience of lawyers and seeking their advice you would probably have came to the conclusion that some are good some are decidedly not but they all think they know what's best. I as of a certain age listen to advice sometimes act on it but at the end of the day its my judgement to go with it or not and certainly would not hold free well intentioned advice accountable. If I learned a valuable lesson on applying force even as I believed controlled to the upper end of a train can cause this effect then prudence should kick in obviously in line with one's experience and downside risk. Obviously turning the star wheel works most times unfortunately I threw it away but not before clamping the gear wheel in pliers and testing the star for rotation...it was stuck very tight and I could not move it. It was a very old clock, not worth a been or even attractive. That's why beginners should learn on old clocks (preferably their own) as hands on experience is a large factor in horology. I am a human being and will make mistakes but hope to reduce such incidents as my knowledge improves. Score to date 3 clocks including a balance wheel escapement repaired and have kept going and one disaster......probably not to uncommon for a beginner.

    Regards
    CC
     
  26. Jay Fortner

    Jay Fortner Registered User
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    Your average will get better with practice.
     

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