Why your Nonus could be stopping after 2 or 3 cycles.
  • The crucial phase with the Nonus is when the drop weight hits the pendulum pallet.

    In order for it to work correctly the first point of contact when the drop weight rollers hit the pallet has to be on the top of the pallet.


    The pendulum continues to advance slighty with the rollers pressing down on the pallet then gravity kicks in and pulls the pendulum into its return swing, this is when the rollers slip off pallet top and run down the pallet impulse face giving the pendulum the necessary momentum for the next 60 seconds.


    Instead of the first contact point being pallet top it can be pallet impulse face.


    What happens here is that the pendulum is still continuing its swing but is braked by the rollers hitting the impulse face, the pendulum continues its swing but loses a lot of its momentum by lifting the drop weight slightly before it starts on its return swing.


    Then the drop weight impulses the pendulum as normal, but as the drop weights impulse force is only enough to keep the pendulum swinging it can not compensate for the lost momentum, and the Nonus stops.

    You can see this happening in the following video.


    It is in slow motion and if you look closely, and I mean really closely as it is only a couples of frames, you will see the drive weight hit the impulse face and then be pushed upwards slightly by the pendulums momentum before completing its impulse cycle.


    One cause could be a lack of pendulum momentum, if the pendulum is moving too slow at swing extreme it will not have the time to move under the rollers after the triggering of the drop weight, lack of momentum can of course come from the count wheel absorbing too much force over the 60 second period.

    Another cause is that the drop weight is being triggered too soon, the reason for this is that the trigger arm is not correctly aligned to the count wheel, easily done as the alignment is a bit of a hair trigger.
    If it is only a small amount the trigger arm faces as well as the pawl face could be sanded back so that they connect slightly later, but be cautious as too much sanding reduces the length of both parts, which could result in them not contacting at all.
    Another method would be to increase the length of the pallet, by simply gluing on a thin piece ply/wood onto the impulse face.


    The best but slightly more adventurous method would be, with a fine saw, cut through the spacer (10B) between trigger arm and count wheel, and re glue with the trigger arm turned slightly in an anticlockwise direction, causing the drop weight to be triggered slightly later.

  • I have that timing perfect (as far as I can tell). I cut and re-glued the trigger mechanism twice. Still not enough energy to get the clock to keep moving. I tried adding weight to the stop mechanism (as someone mentioned) and even tried using more drive weight. Still it fails. Someone must have gotten this to work, right? What did you do?