Barr & Poole More Barr Clock Trouble

Discussion in 'Electric Horology' started by Ledminer, May 31, 2010.

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  1. Ledminer

    Ledminer New Member

    Apr 22, 2010
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    I recently acquired a Barr battery clock. It was somewhat dirty and not working. Examination revealed that the roller on the gravity drop arm was contacting the spigot on the pendulum crutch even when in the raised position. There is a small coil spring restraining a moving part of the locking system on the bottom of the drop arm. This seemed to be over-stretched allowing the arm to "sag". Replacement of this spring by a tie of sewing cotton (!) cured the problem and the clock worked. The cotton has since been replaced by a newly wound spring. This seemed to be a critical area and several springs have been tried as I thought some "sag" was probably advantageous here. Not so - the strongest almost immovable spring gave best operation.

    However, the clock did only 4 or 6 swings between impulses.

    Cleaning is suggested as the answer to all ills so this was done: solvent soaking, ultrasonic clean, pegging out holes and polish pivots.

    Still only 6 swings!

    Motion work removed leaving only the escape wheel and ratchet arm. 6 swings!
    Removal of the escapement leaving only the pendulum and drop arm gives 60 to 70 swings.

    It seems the escapement system is at fault. The wheel revolves very freely but there is quite a shock noticeable as the escapement operates. Some reduction of depth might be advantageous but there is no obvious way of doing this.

    Where do I go from here?

    I am also puzzled as to the principle of operation of this clock. The pendulum is given an impulse by the fall of the drop arm, which is apparently re-set electrically. But it is not! Fall of the arm completes the circuit causing the armature to be attracted to the horizontal position between the electromagnet arms. There it stays until the circuit is broken. As soon as the circuit is broken the 2 coil springs return the armature and it is this which lifts the arm and re-sets the toggle mechanism. How is the circuit broken? When operated by hand in slow motion the break occurs when the pendulum hits the roller on return swing. This is counter-productive as it takes energy back from the pendulum. Observation of the clock in motion (difficult) seems to indicate that the circuit breaks before the pendulum returns. Perhaps the natural resonance of the arm and contact springs cause a bounce?

    Any information?
     
  2. RickB

    RickB Registered User

    May 28, 2010
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    It looks like none of the experts are going to reply, so I will.

    I had a Barr a few years ago, it worked fine so I never really learned to troubleshoot it.

    I know mine didn't like oil, it ran well clean and very little oil. I was told not to use any oil at all but I didn't want to run it dry.

    They came with a level for a reason.

    I did save a few links about the Barr and Poole clocks, maybe you will find something that might help. Sorry I could be of any real help to you.

    http://www.davewestclocks.co.uk/BAR%20Electric%20clock.htm

    http://nawcc-glar.com/2003exhib/04.html

    http://uv201.com/Clock_Pages/poole.htm

    Good luck, I hope you figure it out. :cool:
     
  3. antiekeradio

    antiekeradio Registered User

    Mar 1, 2010
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    the 'no oiling' part obviously only applies to the parts that move on impulse.

    you might be able to set the depthing of the pawl that hits the wheel, just like on ATO clocks.
     
  4. Ledminer

    Ledminer New Member

    Apr 22, 2010
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    Thanks for trying chaps. I knew the links RicKB suggested but no extra info there. I was hoping for a magic bullet.
    Oil or no oil makes no difference. Well, it wouldn't at just 6 swings between impulses would it.
    I have repeated the test several times. Just the pendulum (nothing to oil there except the roller on the drop arm) nearly 70 swings. Add the escape wheel (with or without the pawl!) brings it down to 6.
    Must be the escapement causing the trouble. I shall closely examine the arms which operate the wheel but I am reluctant to start bending anything.
     
  5. Ledminer

    Ledminer New Member

    Apr 22, 2010
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    The end of this story - perhaps!
    After several months of experiment I now think I know more about what makes this clock tick!

    First; the “depth” of the arms which move the ratchet wheel were excessive. One arm was trying to move the wheel on while the other was still obstructing it (figure 1). Judicious bending of the tabs on the pendulum crutch arm (figure 2) solved that one. I haven’t got this quite right as the clock sounds slightly out of beat when levelled and I think this is due to uneven depths but it is very difficult to get right.

    Second: all the springs in this mechanism are critical. Several on my model looked over-stretched and experiment proved this to be the case.
    The tiny spring on the locking mechanism (figure 3) certainly was no good as it allowed the drop arm to sag so that the roller hit the stud on the pendulum arm every swing. I am not sure of the purpose of this spring as I first replaced it with sewing thread, which had almost no “give”. I have since replaced it with a much stronger spring, again with little give, and it works fine.
    It then became clear that the spring which helps pull down the impulse arm (figure 4) could be stiffer to give the pendulum a stronger impulse. That then revealed that the two springs on the front of the plate which hold the armature in its rest position were stretched, allowing the armature to move and again letting the drop arm touch the stud on the pendulum arm. Stronger springs there too.

    I now have a working clock, which keeps time and does 48 or more swings between impulses.
     

    Attached Files:

  6. darrahg

    darrahg Moderator
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    Dec 22, 2006
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    Thanks for sharing. Good trouble shooting!
     

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