I thought you might like to hear more about my experiences with the stopping problem.
I built the 10 day clock in August, and had it run reliably for around 5 weeks, after which it began occasionally stopping. Eventually it got to the point where it was stopping twice or more per day. We discussed this a bit at myminifactory and on discord, and I decided to reprint everything using regular hatchbox PLA instead of silk PLA. When I rebuilt the clock, I also re-cleaned the bearings and lubricated them with dry PTFE, and picked the best ones by spinning them on a 3mm shaft and counting how long it was until they stopped.
After reassembling the clock it ran with less weight than before (down from about 7.5 pounds to 5.5 pounds). The pendulum swing was +/- 3 degrees most of the time, occasionally a little less. It ran reliably for 14 days. This morning I noticed the swing was only +/- 2 degrees. From when I set the beat originally, I know this is about the minimum that will work. This evening, the clock stopped. I noticed that if I restarted it with the pendulum swinging ~5 degrees, it decayed back down to 2 within a minute or so.
I've just tried removing the pendulum+anchor and its arbor and reseating the bearings. Spinning them on a 3mm shaft as before showed they still run for as long, so I don't think they need further cleaning or lubricating. I also noticed the dial had a little (tiny amount) play due to some unevenness in the top of the base, so I sanded the top of the frame to smooth this out. Too early to tell if I've fixed the problem, but after an hour the pendulum is still showing a healthy 3 degree swing without quickly decaying to 2 degrees.
Not sure what to make of all this. It eliminates silk PLA as being the problem for my clock. I've noticed that bearings are a loose fit in their hole (likewise the arbors), and this is something which can vary from one printer to another. We'll see what happens over the next few days (weeks? hours?). I did rewind the clock just 2 days ago, and it makes me wonder if this might shake the bearings out of alignment causing extra friction. It would only take a little extra to cause problems. The first half of this video (https://www.youtube.com/watch?v=FKpRrlZuuZo&t=88s&ab_channel=woodentimes.com) has some observations about the effect of misaligned bearings.
If it stops again, I think I might try putting a little shim round the bearings to hold them in place better. I've done this on other projects by sticking a tiny piece of tape round the rim. Maybe polishing the arbor more would also help.
I'm interested in any thoughts about all this.
Thanks for the detailed writeup. Misaligned pendulum bearings can certainly add friction and reduce the swing. I deliberately made the mounting holes slightly oversized to let the bearings settle into position. Adding a piece of tape and aligning the bearings as shown at woodentimes is a great solution. You would have to use a shortened arbor.
I have tried finding a pendulum support that has lower friction than bearings. Good (and well aligned) bearings work great, but they can be problematic. A music wire suspension spring is a possible alternate solution. I also might try using two pairs of rare earth magnets to let the pendulum hang.