Pendulum weights
  • How critical are the weights in the pendulum bobs? I used discs made from lead but didn't measure the weight of them. I get the 50 second swing OK but can't get the clock to run for more than about thirty seconds. I have found I have had to increase the weight of the bob on the end of the left hand pallet to get it to move clear of the escapement wheel.
  • As I understand the construction, the weights in the pendula bobs control the period of the pendulum and should have nothing to do with the lenght of time the clock will run.
    I too had to add weight to the left hand pallet to get it to swing back and release from the escapemwnt wheel cleanly.
    When I set my Sextus up it was a case of adjusting one variable at a time.
    Friction in the rest of the train could be an issue.
    I found the position of the counterweight arms on the pendula to be quite critical and, and they are not as suggested in the build manual, mine area actually very close in.
    Drive weight could also be an issue, mine wouldn't run for long, so I increased the weight, no joy, ended up with 5kg on there, no joy, ended up with less than 2kg in the end....reducing the weight made it run longer!
    Do try concentrating on one variable at a time!
    My Sextus has been running for some time now, but will occasionally stop and require a tweek of something!
    Fustration but rewarding!

    Good luck.

    Chris.
  • Finished the clock and, of course,it does not work at all. The pendulums each swing for more than 50 seconds so that is not the problem. All the cogs move smoothly before attaching the pendulums.Weight is exactly 2.0 kg so that is not the problem.

    Do the pendulums have to be straight at a 90 degree angle to the frame to start? Is that the problem? When the pendullums swing the escarpment cog does not advance at all. Is that because the pallets are too tight or too loose and the springs need to be adjusted?

    I expected the clock not to run accurately without a lot of adjustments, but I did not expect it to not run at all. The I attached the weight and swing the pendulums and they swing for about 3 seconds before stopping completely.

  • Correction. I meant to say 2.9 kg weight..although I suppose that it really doesn't matter since nothing moves anyway.
  • DavidN

    You write "Finished the clock and, of course,it does not work at all" what went seriously wrong during the build that it is a foregone conclusion that it would not work?

    As Chris mentioned above concentrate on one part at a time.

    Please also watch and follow the advice given in the Ball Bearing tutorial as mentioned here :-
    Elusive Tick


    You will also find a post from RichardD who mentions that one of his pinions had a small remnant of a holding tab on one of the teeth, which binded with the cog and blocked the gear train, which goes to show that attention to detail is paramount as it can sometimes be the smallest thing.

    There is no magic solution, as any clock relies upon the fact that each "component" does its job, which is why it is important to thoroughly check each part, as mentioned in my Tutorial :-
    The Elusive Tick



  • DavidN

    Your pendula are coming to a halt in a few seconds because the pallets are not releasing from the escape wheel and essentially holding the mechanism back.

    This could be for 2 reasons :-

    1) Friction. If you watch the pallets, they only release from the escape wheel when the amplitude of swing of the pendulum exceeds a minimum. Friction in the drive chain will restrict the drive force exerted by the escape wheel on the pallets, and the amplitude of the pendulum will fall too low. Your pendulum swing figures are not great, and you may also have friction elsewhere in the drive train. Going through the mechanism polishing all the rods and gear teeth will pay dividends. With a good polish, it is possible to get the pendula to swing as a pair for over 2 minutes without the escape wheel in place.


    2) The pallets do need adjustment for them to engage the teeth properly and release when they are supposed to. The clock will only work when the point of the escape wheel tooth engages perfectly in the angle of each pallet. Dave's instructions show how to carefully file the pallets to achieve this. The left hand pallet is sometimes reluctant to clear the escape wheel, and this can be corrected by adding a small counterbalance weight such as a blob of blu-tack.

    Best of luck.

    Paul