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Just Wondering....

I have built just about all the wall clocks especially my favorite one the moon phase clock. They've all been running fine for months up until a few weeks ago. Now not one but every clock is stopping on me. I've taken them all down taking them apart re clean the bearings dusted off anything checked every gear put it all back together put it back on the wall. Started it up again and again in a few hours they all stop. Has anyone else been having this problem? Also I've noticed the hands on the clock have become very loose some of them falling off and just hanging at the 6:00 hour. Push them back on but they seem to wiggle off again. This is just a little disheartening when you put so much into making these. Any ideas or help would be appreciated.

3 comments

3 Comments

kicksnj2

18h

Steve, I have already cleaned the bearings again. Even bought ceramic bearings in one of the clocks. Cleaned and checked all the gears grease them. I'm going to do what you're thinking of doing. I just went and ordered a load of PETG PLAIN AND SILK and I'm going to redo one of the clocks entirely in PETG. Maybe I should try and test the new gears you created in PETG? Also I'll have pictures for you soon. After months of tinkering with the SP7 electromagnetic desk clock I finally made a lot of modifications to it and the clock now runs on a 4.7 volt battery with a built-in recharging system USB-C port in the back of the clock so the clock can now run either electric or battery and if you run it off electric it automatically will charge the battery for whenever you want to not use the cord. It seems that this higher boost and power created a much more stable magnetic field. And the clock is very accurate now. Also I re-did the pawls and added rubber bumpers that hit the gears so there's barely any noise from it and also the rubber bumper keeps the gear dead still from moving backward so that the second hand has that back and forth motion. That has completely stopped now. Let me know if you want me to try the new gears with the PETG. I'm getting all the filament tomorrow.

Steve

16h

Replying to

PETG is worth a try. I also have some on order that will be here Wednesday.

My suspicion is that involute gears have more engaging friction than cycloidal gears. This is where a new tooth starts to engage. If it engages before the line of centers, it pushes into the other gear and friction can be higher. Any engagement after the line of centers is pushing away with low friction. This effect can be seen in the ratchet that often sticks in one direction but easily slides in the other direction. A thin layer of lithium grease solves the problem in the ratchet.

I believe the same engaging friction issue is happening with the involute gear tooth profile used in many of the clocks. A brass gear with steel pinions does not dig in like softer PLA. That is why I have been trying new gear tooth profiles. If it works, then I will populate the gears to some of the other clocks. The initial results look promising.

The pendulum free-swing test will quickly determine if the bearings are good. I have never seen less than 98% of the cheap bearings pass the free-swing test. Ceramic bearings probably work better but should not be required.

Steve

18h

I see the same thing. Several clocks that were working great will stop running after a few months. Knowing how they stop helps to debug the issue.

Does the escapement still have good energy? Or is it sluggish?

If the escapement still looks good, then the bearings may need cleaning again. There may be the last residual grease still left in them. Cleaning the bearings again brings the clock back to life. This problem occurs about half of the time.

The remaining cases are from changes in friction. I usually drill out the arbor and frame holes again. It may also be that the PLA changes over time. All of my clocks use silk PLA because it looks so good. Does it get sticky after a few months? My oldest continuously running clock was printed with bronze PLA. It is probably from before silk PLA became common and it ran for over 5 years without any change in performance. Greasing the pinion teeth reduces friction considerably with silk PLA. Just a tiny bit on each pinion tooth is enough. It works its way around the gears.

I am also trying out new gear tooth profiles that might help. I re-built the 32 day clock with the new gears. The clock is running in 32 day mode with 6.4 pounds of weight. I will keep it running to see if it changes over time. PLA supposedly creeps. I may also try a clock using PETG for the gears to see if there is a difference. I am also open to any other suggestions.

The hand tightness may also be due to PLA creeping over time. They are small enough to print again.

Steve