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Full Version: Improving pendula swing times.
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A critical part of the Sextus are its pendula, as they are at the end of a long gear train they receive the least amount of drive force and if they are not swinging as efficiently as they should then it will prevent your clock from running.
A major source of friction can be the rear bearing on the pendulum arbor, a simple way of reducing this is to shorten the arbor and chamfer the end so that it just about sits in the bearing but can easily move around.
The main weight of the pendulum is supported by the front bearing and the rear bearing is merely to keep the arbor in position.
You can test this by simply comparing the swing times of the pendulum in its original position and when you have moved the pendulum forward by
loosening the ring stops so that the arbor at rear just about sits in the bearing, you should notice some improvements.
I first built my Sextus a bit over three years ago and after some tweaking and adjusting had it running fairly reliably. I spent quite a lot of time playing with the pallet tooth shape to get the pallets to properly lock the escapement wheel and then release it; as part of this I also added a very small brass weight to the LH pallet to get it to swing away from the wheel teeth more cleanly. However, it was hanging in a temporary location on the back of a door and one day I forgot it was there and shut the door, catching the pendula on the door frame. After that, it did not run for more than a few minutes at a time!

It was put to one side and I have just started getting it running again. I think the frame had become very slightly twisted which was adding too much friction to one of the pendulum pivots. I seem to have now fixed that and it runs for a day or so at a time; it does not stop by itself, only when I need to stop it to tweak the timing adjusters. I am now running it with about 3.2kg although it seems to be gradually running in and the pivots are easing up. Testing just now with the pendula geared together but with pallets removed gives a swing time of 65-70s, which seems reasonable. I don't want to disturb the pivots to test the pendula individually!

It's a fun clock to watch in action although it took a bit more work than I expected to get it running. Still, I seem to be almost there now - just trying to get the time-keeping about right. I agree with the above comments about ensuring that the pendula swing freely - this was at the heart of my problems but it took a while to get to the real issue.