Beat adjustment mechanism

Discussion in 'Clock Construction' started by dandydude, Nov 15, 2015.

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  1. dandydude

    dandydude Registered User

    Nov 30, 2014
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    Hello,

    I have supported my pendulum suspension spring from a threaded rod which is supported on V grooves on a Stainless bracket. The bracket is mounted on the back of the case as is commonly done in a lot of precision clocks. I have made a mechanism to 'beat' adjust the crutch pin (threaded rod going through a 8mm crutch pin). This again is the common detail that i have come across in a lot of precision clock literature. However the mechanism is too heavy and is sagging backwards (towards the movement, not towards the pendulum.) i could make it a little lighter, but i was wondering whether the beat adjustment is required at all? cant the threaded rod (supporting the suspension spring) on the 'V' grooves of the bracket be moved left or right a wee bit for the beat adjustment?

    I hope the image attached makes sense...

    Thanks
    Dandy crutch-beat-adjustment.jpg
     
  2. Phil Burman

    Phil Burman Registered User

    Mar 8, 2014
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    Sketch?

    Phil:)
     
  3. dandydude

    dandydude Registered User

    Nov 30, 2014
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    Dear Phil...
    There is sketch attached to my post. Don't know if its very clear.
    Thanks
    Dandy
     
  4. harold bain

    harold bain Registered User
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    Nov 4, 2002
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    The beat adjuster should be on the crutch, not the pendulum rod/suspension.
     
  5. Tinker Dwight

    Tinker Dwight Registered User

    Oct 11, 2010
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    The only issue I see is that as you move sideways, you reduce
    the gap to the crutch and the crutch will slide up and down
    more as it swings. May clocks had different length arms
    on the crutch and pendulum that worked without too much loss
    so, as long as it doesn't bind it should work.
    Tinker Dwight
     
  6. dandydude

    dandydude Registered User

    Nov 30, 2014
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    Dear Tinker,

    Iam using an assymetric crutch. So i dont think binding should happen. Whe i tested it with 3D printed plastic rod, it seemed ok, but the metal crutch seems to be be too heavy. I dont want to the stress the palet or the palet arbor with too much weight. The sketch is as per your suggestion. There is a threaded rod. the ends of the rod would also be threaded so that the suspension can be locked with nuts once the pendulum is stable. Cant this system be used for beat adjustment? move the rod a little and then tighten the nuts. its a bit less user friendly though.

    Thanks
    Dandy
     
  7. dandydude

    dandydude Registered User

    Nov 30, 2014
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    Dear Harold,

    I was testing a beat adjuster on the crutch. It is getting a little heavy with my design. This is why i thought why have a beat adjuster, why not just move the threaded rod that suspends the pendulum a little to the left or right and tighten it with the nuts.

    What do you think?

    Thanks
    Dandy
     
  8. tok-tokkie

    tok-tokkie Registered User

    Nov 25, 2010
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    There is a principle in engineering called 'inversion'. What you are proposing is a very good example of it. Instead of adjusting the pallets and leaving the pendulum as is to set the clock in beat you are wanting to do the inverse = leave the pallets as is and instead adjusting the pendulum. It should work just as effectively for adjusting the beat.

    Problem is for precision timekeeping you want the top of the suspension spring to be really rigidly anchored. I think you are going to compromise this aspect.
     
  9. dandydude

    dandydude Registered User

    Nov 30, 2014
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    Dear Tok Tokkie,

    I have already been warned by Tinker to not do the inverse. However what iam trying to do is still a rigid support for the pendulum. Only that the nuts securing the suspension rod on the bracket are going to be loosed when beat adjustment has to be done. once adjusted the nuts at the ends of the threaded rod are tightened to hold the pendulum firm. This was i can avoid over engineering the crutch adjustment. In fact iam trying to avoid the beat adjustment itself... is that ok to avoid it?

    Regards
    Dandy
     
  10. tok-tokkie

    tok-tokkie Registered User

    Nov 25, 2010
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    I realised I had written pallets where I should have written crutch but you have got my meaning.

    Normally the upper chop of the suspension spring is a snug sliding fit into a slot in the cock. It can not rock from side to side. The pivot point of the pendulum is the flex point of the spring.

    If the upper chop is not properly constrained on its sides it will tend to rock from side to side. The pivot point of the pendulum is then the sum of the side to side movement plus the flex point and that can be variable so the precision of the timepiece will be somewhat variable too.

    If you are happy that your system will not allow any rocking then it should be fine. However accurate clocks are remarkably precise. 1 second a week is much less than 1 in half a million. That gives you an idea of how precisely consistent the pivot point of the pendulum needs to be. You seem to want to keep the crutch simple by eliminating the beat adjustment from it. You have not 'avoided the beat adjustment itself' for you have moved it from the crutch to the suspension - you will still be able to adjust the beat. I like your idea but I fear it will be at the expense of the precision of your clock. Let's see what the well informed have to say.
     
  11. GregS

    GregS Registered User

    Sep 4, 2008
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    When the movement is cased and the dial installed, will you be able to reach it?
     
  12. dandydude

    dandydude Registered User

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    Dear Greg...

    Good point... I dont have much of a dial... its a very skeletal clock i have in mind. The suspension point (point of flex) is the same height as the palet arbor. This is right on top. I guess you could slide in your hand and adjust. You just got me a little concerned though about whether i could see what iam doing once i access the adjustment. Thanks for pointing out.

    Regards
    Dandy
     
  13. Allan Wolff

    Allan Wolff Moderator
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    Mar 17, 2005
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    Here is a photo of an adjustable suspension bracket for beat adjustment that I'm told was invented by James Condliff. Might give you some different design ideas.
    Allan
    mp5a.jpg
     
  14. dandydude

    dandydude Registered User

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    Dear Allan,

    Thanks for that image. At least i know iam walking the trodden path...

    Regards
    Dandy
     

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