It looks like I have finally found a fix for the "sticky gear" issue that has been causing the easy-build clocks to stop. A clock can be running perfectly and suddenly the escapement stops rotating when the pendulum is moved back and forth manually. The clock can be made to operate again by pushing on the escapement, but the problem has not been fixed so the clock will only run for a short time.
The root cause is gear 3 pushing against the escapement and preventing it from rotating. It takes very little sideways pressure to stall the escapement since it very lightly loaded. Straight spur gears should not have any sideways motion, but it seems like they do. The cause could be frame sag, not perfectly level walls, or gear 3 tilting so it gets pushed sideways. This problem has been particularly difficult to debug because the symptoms do not change when the drive weight is increased. Now it makes sense because a heavier drive weight will apply a proportionally larger pressure against the escepement.
The fix is to add a gentle helical twist to gears 3 and 4 to push gear 3 away from the escapement. Gear 4 has five different runtime options, so the complete fix requires a new gear 3 and the appropriate runtime option of gear 4. Both the 32 day and the larger 21 day easy-build clocks are affected by this issue.
Here is a picture showing a small helical angle on the large portion of gear 4 in the front and the pinion on gear 3 in the back of the image.
This solution was prompted by a series of questions on MMF by Felix. I ran some tests to confirm the hypothesis. A previously buggy clock was brought back to life with a large pendulum amplitude. A clock with a reverse helical angle to exaggerate the issue will typically stall within 5-10 minutes.
The new gears have been uploaded to MyMiniFactory for both sizes of the easy-build clocks. I will try to post a video describing the solution soon.
I am trying this fix now. I built the 10-day version last August and get a consistent pattern of about 4-5 weeks of reliable operation before I saw the pendulum swing getting less (on average, as there is always some variation), before it stalled. Restarting might get a few more hours or a couple of days further running. Each time I disassembled the clock and fiddled with it in various ways, only to have the pattern repeat after 4-5 weeks. In February I switched the escapement to ceramic bearings, and it ran until June before stalling. After a restart it ran fine until the start of July since when I have had two stalls. I've now replaced the two gears with the new variants and we'll see how it does.
Yes, silk PLA should be perfectly fine to use now.
Glad to see a fix! Does this put silk PLA back on the table? I've been wanting to build an EB for a while, but had kind of been set on the look of silk/metallic PLA before you posted about the issue, and haven't been able to find a "regular" PLA I was happy with for this application.