Jared Fenster- Made Wave Generator Separate from planetary gears so it can be optimized faster.
After playing around with the shape of the wave generator, I found that it controls everything. after a few attempt I was able to make the Joint Back drivable once fully assembled. I have modified the shape of the wave generator to optimize of tooth contact. I believe I have found the perfect shape, but currently when using this shape there is too much friction for the ball bearings to move. I will be working to fix.
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Is there anything more to it than the eccentricity of the ellipse? Normally that's determined by the tooth count. The ring is 2 teeth larger, so the ellipse needs to increase the diameter of the flexspline by 2x pitch to get it fully engaged, and decrease by 2x pitch in the other axis to maintain equal circumference.
It is possible to cheat and use less eccentricity by clever tooth design, but it results in fewer teeth engaged because the flexspline teeth have to be narrower than the gaps between ring teeth, so the ones at the center of the engaged area are not actually touching anything.
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The solution to my issues was to have one axis equal the flexspline + 2x tooth height, but on the other axis it actually worked better when I just subtracted 1.75mm from the flexspline diameter. For reference, the tooth height was something like 2.55mm.
On the first few attempts I did exactly what you said (subtract 2x pitch), but for some reason that did not give optimal tooth contact. At that time, the non-engaged teeth of the flexspline where quite far from the teeth of the circular spline.
So yes, from my work I found that the eccentricity of the ellipse determines everything, but for some reason (probably the fact that its plastic) the normal way does not work.
Are you sure? yes | no