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Extending the soundscape of a hexaphonic guitar pickup
sorveltaja:
Today, after finding this video, I got stuck in the idea for printing the reduction gears for the pot, after all:
As can be seen, fewer and bigger gear teeth are used. There is a link to Thingiverse for the 3d model in the video description.
There seems to be quite a lot of slack between them, which could probably be adjusted in the slicer settings. Haven't got much into that, so I rather redraw/modify the gears using 3d software.
When there are sun- planet-, and ring gears involved, trying to figure out the gear ratios makes me feel dizzy, so it's better to just print out some samples, and see, how it works.
Nothing critical about the gear ratios, so any result, that 'feels' good enough for the purpose, is worth testing with actual potentiometer.
At first, I'll be using simplified tooth shapes for sketching:
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This will be a short sideproject, to see, if the concept is relatively easily implemented, as I don't feel like delving into it too deeply at this point.
sorveltaja:
The "potentiometer gear reducer" -side project goes on: I noticed, that gears with straight teeth don't work so well in this case, so helical ones would be better.
Test setup for gears with 45 degree angle:
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Idea came from this:
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Printed parts:
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So far, it seems to work as expected. For now, tolerances are bit tight, but it's just a matter of playing with the offsets of the gear profiles.
Also, as the gears are helical, they tend to 'climb' up or down, while turning back and forth. Some sort of support structure needs to be added to keep them in place.
Currently the footprint, or outer diameter of whole thing is 30mm.
Sea.dog:
I'd suggest printing them as Herringbone gears which have no side thrust. The downside is that the outer would need to be split so that it could be assembled from each side and then joined at the separation line. Or maybe the gears could be printed as two halves that come together with pegs to engage them. They'll still require some means of gluing or a snap-together fitting so that they don't part company in one direction.
sorveltaja:
Seadog, thanks for the idea! I tested it and it works very well to keep the gears in place.
Assembling the thing, yes, it's a bit of dowside, but somehow I managed to cram the gears together.
With the gear sizes, that I've tested do far, the reduction ratio is close to 4(by eyeballing, while rotating). Sun gear has 5, planet gears 8, and ring gear has 22 teeth.
To simplify the thing, I guess only one planet gear(blue one) might be enough, as there aren't much of forces involved. With small, printed gears, there seems to be always hideous tight spots, so reducing the gear count is an attempt to minimise that:
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If more gear reduction is needed, there would be room for that also:
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To get less wobbly action, the sun gear should probably use a metal rod(2mm in this case), attached to the green part.
As an alternative for using gears, plain friction based one, as on a picture on the previous post, should make the desingn a lot more easier to build. Using the steel balls would require very tight tolerances, and is therefore beyond the scope.
Again, one possible option could be to use something like rubber as a material for the planet gear, which otherwise causes the tight spots.
Joules:
I think you are getting confused with the ball bearing pot. They are no more precise to make than a 3 legged stool, the use of 3 bearings (the items of precision) allow the shaft to self centre, a bearing pot can slip. It relies on two conical surfaces to work, the shaft is tensioned to maintain friction. As the shaft and cone wear, the ratio of turns also changes, slightly. Do you want repeatable location (geared) or high resolution of motion, the two are not the same.
The tight spots in prints will always be present in a cartesian printed part, they can’t produce accurate round components. The best you can hope to achieve in extruded filament is using a delta printer as they have no XY backlash, but plenty of other setting issues. Resin printers seem to produce some of the most accurate gears I have seen as they have such high resolution and consistent blob size.
Reducing your nozzle diameter, will also allow more accurate parts to be printed, but a higher level of printer tuning is also required.
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