Debug Hints

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Moon Dial Moving Too Fast

The rest of the clock seems to be working perfectly, but the moon dial is FLYING compared to how fast it should be going. Honestly, closer to a quarter turn each day. I haven't had the time to check, but I'm guessing that clutch set is too tight or maybe I have too strong a spring in it or something. Is it possible to have too strong or too weak of a pen spring? What are the optimal specs of the springs that should be used in the clutches? I've been using 0.5x5x20mm in the past without any noticeable trouble, so I never thought that they might be putting too much friction into the system. Now with adding the additional gears for the moon phase, it's made me think about that potential. I also have 0.3x4x25mm that I use for ratchet assembly.

Edit: After pulling things apart and taking a closer…

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Steve

4 days ago

The normal operation of the moon dial is powered by the hour hand gear. Two stages of gear reduction turns the moon dial with a 59 day cycle. The moon phase friction clutch passes through gear 5 where there is room for the spring. Gear 5 sits between gear 9 and the moon phase friction clutch. The moon dial sits between gear 6 and the front frame. There is a lot going on in a very small space.

If the moon phase is rotating too fast, then the moon phase friction clutch is slipping. That alone doesn't indicate if it is an issue with the friction clutch or the gears binding up.

The easiest way to debug this would be to remove all the gears except the central arbor and the gear 5/9 arbor. This allows you to only the gears of interest. Rotate gear 4 to move the minute hand while observing the rest of the gears. There should be minimal resistance if all the downstream gears move freely as intended. If there is any binding, then rotating gear 4 would need enough force to allow a friction clutch to slip.

Steve

March 4, 2026

SP5B Weighting

After some minor tweaks, my 12-day clock ran for 2+ weeks including a winding or two and was keeping excellent time. It's using 4.4 kg of weight with the fishing line loop as designed. Although the weight is a touch heavy, I was just happy it was running so well. Then I woke up one morning and it had stopped. I was able to get it to run again for anywhere from minutes to hours by making minor adjustments but then it would stop.

I took the fishing line loop out and suspended 2.2 kg directly planning to run it without the escapement but before I could do that, it's back to running like a champ again--16 hours straight. I tried the loop with 4.4 kg and it stopped again. As I write this, it's running great with 2.2 kg direct hang.

Any ideas what could be going on?

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Steve

Mar 04

If the clock works with 2.2kg direct and stops with 4.4kg plus a pulley, and nothing else changed, then the pulley must be the problem. More likely, something else changed. It is easy to check the pulley just in case.

Two things to check after the clock stops are the escapement and the pendulum. It's even better if you can observe the clock just before it stops. Does the pendulum slowly lose amplitude? Or is the escapement losing energy?

Move the pendulum back and forth slowly while observing the escapement. Does it have the same energy as before? Then check the beat. Does the escapement tick and tock at equal amplitudes from side to side?

This clock has a friction sensitivity with gear 3 and the escapement. Sometimes when the clock is being adjusted, the frame can be squeezed and the escapement shaft collars get moved. This can push against the escapement. The slightest amount of side thrust against the escapement can stop the clock.

Hopefully, this provides some help.

aleitner

March 2, 2026

Clock used to run reliable, but no more

Hi Steve! First of all, thank you very much for these clocks! They are amazing!

I printed and assembled a SPB5 with the 15 day option. After a bit of tuning and reducing friction using your awesome debug hints I got it to work reliably. I went on vacation and even after a week it was still ticking just fine.

Then I decided to take off the weight shell (for an inspection) and put it back on. I didn't change anything else. Ever since then the clock is not running reliably anymore. It runs for a few hours at most, sometimes maybe just for a few minutes. The pendulum amplitude gets smaller and smaller till it completely stops. (I can restart it very easily though with just a gentle push of the pendulum)

Since then I tested the gears in isolation (without the pallet) and the weight (of ~6kg) drives…

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aleitner

Apr 26

So now the clock works and i don't know exactly why. But it has been working reliably for a few weeks now. My kids kept restarting it and eventually it just kept going. I don't know for sure what the problem was. One hypothesis would be that the finishing line was not wound up well. But it is just a hypothesis. In any case now it works and after some adventures with a broken printer I am trying to print a second one now.

Thanks again for your support and for this awesome design!

Andreas

February 18, 2026

Gears Not Moving With Weight Attached

Hi Steve!! I love all your designs! I built the easy-build wall clock, but the gears won't move freely when the weight is installed. I reversed the Pendulum just to see if the gears would budge with no interference. No luck. I have taken the clock apart and rebuilt it several times now. All the gears on the left side work great on their own. All the gears on the right side work great on their own. When all together, it takes a ton of force to get anything to budge. Please help! I look forward to having your other clocks built. But need this one working first.

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Steve

Feb 18

It takes a surprisingly small amount of friction near the escapement to stall the gear train when there is around a 500:1 gear reduction. My guess is to look on the right side close to the escapement.

The debug steps should be listed in the assembly guide. Here are the important ones:

Every gear must be drilled to be loose on the arbor.

Every gear needs to have some end shake after assembly into the frame.

The gears that pass through the frame need to rotate freely. This would be gears 6 and 9 on this clock.

Gear 3 behind the escapement is connected solidly to arbor, so the arbor must rotate freely inside the frame.

If all of these checks pass, then start removing gears one by one to see if you can identify the trouble spot. Start with the escapement, then gear 2, 3, and 5. You may need a spacer to hold some of the gears in position along the arbor for some of the steps.

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