I made the previous iterations of SP5 a couple of years ago, and I recently tried out SP5B. I want to try some experiments on ways of reducing friction and hence the drive weight, so I am running it very close to the point of stalling. If the experiments prove interesting, I'll write up the results. One thing I noticed is variation in how strong the tick is. You can hear it, and also when running close the lower limit on the weight, you can have a weight which works for a while and then stalls.
I think the reason, or a part of it, is the set screw for gear 3. I could see that gear 3 was not quite square on its arbor. When I loosened the set screw, it became square and the tick became much more consistent. It also requires less weight overall, as you don't need extra weight to power it through the points where the tick is weak.
Possible remedies are to be much more careful in drilling out the hole so that it is a close as possible to the shaft size. I was using a 1.6mm drill bit, as you suggest, and maybe I can get by with 1.5mm and a bit of brute force to insert the arbor. Secondly would be to have a set screw on either side of the arbor to balance out the forces. Tightening the set screw just enough and no more helps, but it still imperfect. Another is to not use your approach of opening up the arbor hole to a larger diameter in the middle portion (p27 of the manual - a really good idea, BTW), but keep it at the narrow diameter the whole length so that it might hold the arbor in position better.
Interested in your thoughts on this.
(Note: tried posting this through the groups page. But it seems to time out. Not your fault, I know, but groups in general seems much less usable than forums.)
Clocks have one of the most challenging gearing applications. The start/stop action means that the gears have no momentum to push through a high friction position. The drive weight needs to be large enough to start up again when the gears line up in the worst possible orientation.
Gears cycle through three distinct phases as they rotate. The initial tooth contact has engaging friction with some sliding. A rolling action occurs during the sweet spot. Finally, there more sliding friction when the tooth disengages. Engaging friction is the highest of the three modes and the most troublesome for clocks. Cycloidal gears have less engaging friction compared to involute gears. Switching this clock to cycloidal gears allowed a reduction in drive weight by reducing the engaging friction positions where the tick is the weakest.
Cycloidal gears might be more sensitive to misalignment errors in the center position. The set screw tilting the gear or bending the arbor could be an issue. The screw only needs to touch the arbor. There is very little sideways force, unlike the friction clutch screws that need to hold back the spring pressure.
The gear 3 center hole stays tight inside the arbor up to the top of the screw. Maybe the narrow portion could be extended further upwards to help prevent the screw from tilting the gear on the arbor.
Thanks for the heads up about the groups. Wix is forcing the change by closing down the forum feature. I may have to look into external forum software.