Decimus - Finished but problems - catch arm
  • Hi,

    i finished my Decimus today and tested it.

    I put it on the Base Stand, adjust it, so the Pendulum and the Base pillar are in a plumb line.

    Power it, the coil pushes the magnet and the pendulum and it starts to swing.
    The swing ends about 2-3 cm away from the base edges (sounds all good)

    But the catch arm can´t get to the next tooth of the ratchet geared wheel, about 1,5mm are missed to the next tooth.
    If i push the pendulum by hand, it works.....

    A other thing i have seen, i algin the base pillar to stand square/plimb, put the clock on the pendulum hook and it is not in a plumo line, it is not 90 degrees. it looks like the right side is heavier.... and i think so the back swing (pendulum from left to right) is to short for the catch part to get the next tooth.

    Here a link to a actually recorded video from my decimus:

  • Hi Markus,

    I couldn't actually get your video link to work, but you described your problem very well.
    I finished my Decimus about 6 months ago, and have good experience of correcting problems. It is, without a doubt, my most accurate and reliable wooden clock.

    Firstly, to get the catch engaging properly, the catch arm must swing quite freely. A point which I missed when building mine, is that the left hand counterbalance weight is larger than the right hand one. This is to compensate for the drag when the catch pushes the gear wheel around. I have been experimenting by adding different weights to the left hand side, and you definitely get a larger amplitude of swing with a heavier weight, and a more positive action.

    I also added a small counterbalance weight to the catch itself, so that it pushes upwards more positively against the gear wheel.

    Hope this helps

  • Thanks Paul,

    i don´t know why, but if you copy the line with the video and past it to the browser, you can watch the video.

    And thanks for your hints....
  • So i disassemblemy decimus, only frame and inner gears.... and test a bit.

    1. polished again the brass arbor from the catch arm, add graphite from a pencil.

    Not better...

    But in the instructions of dave, he has written that also a 9 V battery can work with the decimus, so i think the voltage is not a big problem to increase.

    So i connect a universal power supply (5-12V) and set it to 7,5 V.... and it runs good! The magnet drive kicks the pendulum a bit more and the catch gets the next gear tooth.

    So i will assamble the clock again now... stay tuned....
  • I am pleased you now have a working clock.

    I am now able to open your video, and I notice that the pendulum swing is not sufficient, and the catch arm movement needs to be much more vigorous. Something I did not mention before is that the end of the pendulum needs to be very close to the base for maximum energy transfer. My support is a friction fit on the main post, and with care I can make fine adjustments to the height and the angle of swing.
  • Glad to read that you got your Decimus running and at the end of the day that is all that counts.

    But a couple of things I would like to add, when the Decimus is not "plugged in" the magnet will be repelled by the drive coil, so it will always hang to one side or another, but never straight, turn the hands to 9.15 and the pendulum will come to rest on the right side, 3.15 and the pendulum will rest on the left.

    The clock is powered by the pendulum so on its right hand stroke it will pull the pawl back to a position where it can catch the ratchet wheel on the return stroke, this swing uses as good as no energy. On the left hand stroke however, the pawl will advance the wheel and also the whole gear train, which is why the catch arm hangs slightly to one side. What is important to realise is that it is not enough to have a good swing, but it must be strong enough to not only advance the ratchet wheel but also be able to deliver the energy consistently so the gear train can advance.

    It is vital that the pendulum magnet paces over the dead centre of the coil, if not it will not only be pushed left-right but also backwards/forwards which will lose a lot of energy.

    And just as important, as Paul as already mentioned, the closer the magnet to the coil the more energy will be transferred. If you followed the instructions on page 23 then you should have a gap of 2 mm , now by adjusting the fulcrum pins you can reduce the gap and therefore increase the energy.