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Hi Chris,

It seems like there are two issues here. SP4 received the same upgrade as SP5 to improve reliably considerably. You can download the updated SP4B design as long as you can still log into MyMiniFactory using the same account used to purchase SP4. Unfortunately, I believe it is mostly a complete rebuild. The new gears have to be completely replaced. The new gears and winding key require a new frame. So the entire clock needs to be reprinted. The weight shell and pendulum might be the only re-used parts.

Getting SP4 running again often requires finding what may have changed regarding friction. Sometimes the bearings need to be cleaned. Also check for end shake on the central arbor and escapement arbor. A very tiny bit of side thrust can stall the escapement. It may help to add grease to the pinion teeth. Only a tiny bit is needed and it will work its way through the main gear teeth. PLA seems to be resistant to most greases and solvents. The only other advice is to do the debug checklist that you have already completed. Double check that all gears spin on their arbors and all arbors spin in the frame. This is especially true for the gear 3 arbor since gear 3 is attached to the arbor (or at least it is in the SP4B implementation).

Since you also have the new SP5B, maybe it would be best to focus on debugging that clock. If the pendulum swings for 10-12 minutes, why does the clock stop running in less than 2 minutes? Is the escapement rotating freely? Or is it getting in the way of the pallet and slowing down the pendulum? Move the pendulum back and forth manually. The escapement should start spinning immediately when the pallet clears the escapement teeth. Any lag in the escapement starting to spin will prevent energy from being transferred to the pendulum. Check for end shake on the central arbor, the gear 3 arbor, and the escapement between gear 3 and the shaft collar.

The easy build clocks do not suffer from frame sag like the other vertical oriented clocks. You probably don't need to worry about it as long as the frame was printed with 3-4 walls for strength.

Steve

I read lower down that you use Turbocad man did that bring back memories and make me feel old. I have not used turbocad in decades. I am South African so have some memories of being proud that it was developed there haha. I will probably invest time in the new kid on the block then Fusion 360 :P

The 3mm arbor is supported by 623 bearings at both ends.

I did a series of experiments allowing the pendulum amplitude to degrade from +/-8 degrees down to 4, 2, and 1 degrees to measure the decay time. The assumption is that if this follows an exponential decay, then each reduction by 50% should be approximately equal.

Generic 623 bearings with the seals removed and grease removed would typically swing for 15-20 minutes. Metal shielded bearings would only last 8 minutes and rubber sealed bearings measured 6 minutes. Removing the factory grease is critical.

Larger 608 bearings were pretty bad at 7 minutes.

Simple 1.5mm music wire in PLA bushings lasted 5 minutes. 3mm stainless steel rods only lasted 1.3 minutes.

A 3d printed knife edge was pretty bad at 2.5 minutes.

Suspension strings created from sewing thread or guitar strings were all very good with times around 25 minutes, but they would require a pallet with a crutch that would add some additional friction.

I also tried a few rolling suspensions. A 3mm rod inside a 22mm round hole swung for 30 minutes. It lasted less than 20 minutes in a 10mm hole, so I suspect there was some sliding friction instead of simple rolling. These solutions are all susceptible to misalignment difficulties and they would need a crutch that would add some friction.

My intuition regarding pendulum decay time is that the kinetic energy of the swinging pendulum needs to be restored every time the pendulum stops swinging. A pendulum with a 10 minute decay time will need twice as much restoring energy compared to a 20 minute decay time. This energy needs to come from the drive weight through the gears and escapement.

Another side note is that the pendulum is supported between bearings on SP5, while it is cantilevered behind the bearings on most of my other clocks. The cantilevered design would have a load greater than the weight of the pendulum on the back bearing. The front bearing would have an upward force. SP5 is my most efficient clock design, possibly due to lower friction in the pendulum support bearings.

I have had great results using bearings for pendulum supports. My oldest clock has run for 5-6 years and still has a strong pendulum amplitude. There is some variability due to manufacturing tolerances and some people seem to have trouble finding good bearings. I think they work incredibly well. The bearings do need to be allowed to float somewhat. An older experiment with wooden gears using two bearings pressed into position would barely rotate. The bearings need to be able to find the proper alignment. Larger spacing helps as well.

I keep looking for alternatives to bearings. A knife edge that I see in many wooden gear designs had horrible performance in my 3d printed test case. Classic suspension springs are hard to find and often quite delicate. Guitar strings seem like a potential solution that can be easily built by anyone. And there may be a rolling solution as well.

Great question.

The classic design with a 30 tooth escapement and gear sets of 64:8 and 60:8 has a one second pendulum. The 39" pendulum looks great in a grandfather clock but seems out of place in a small wall clock. I wanted the pendulum length to be proportional to the size of the clock.

The only options in a two gear train would be to add extra teeth to the escapement or the 64 and 60 tooth gears. Switching to a three gear train made it much easier to design the entire clock. Now there are three gear sets plus the number of escapement teeth all used to determine the pendulum length. The pinions can have 12 teeth and the main gears would still have less than 60 teeth.

Many of my clocks have a large and medium size variation. The large version often has 1 or 2 fewer escapement teeth to increase the pendulum length slightly. And the horizontal format of SP5 adds more teeth to shorten the pendulum length.

The extra intermediate gear is used for both reasons you mention. I want the pendulum length to be proportional to the clock, and I try to use 12 tooth pinions. Switching from 8 tooth to 12 tooth pinions should more than make up for the increased friction from the additional arbor.

One downside is the escapement rotates counterclockwise and faster than 60 seconds, so the second hand is not available.

Steve

Hole sizes vary all over the place depending on filament diameter, extrusion rates, and different printers. Small holes are almost always smaller than the CAD model. However, sometimes they end up close to the desired size.

If The CAD model was upsized to work for most people, then a few clocks would end up being way too big. It is easy to drill out small holes to fit, but oversized holes have no solution to make the parts fit. So, the only solution that works for everyone is to drill out the holes. Every arbor should be loose except for parts with set screws to hold onto the arbor.

That's understandable.