Daren SchwenkeModel a spring loaded split planet to eliminate backlash. The split will be across the diameter and provide force in one direction. This will spring it against the rotation of the other two planets, eliminating backlash.
<EDIT> Little problem here. The other side of my split planet would be meshing with the sun gear. I would like to keep the sun gear full height as it keeps the forces nicely aligned so I don't need bearings for them.
@Simon Merrett has a decent idea for making the planets slightly 'springy' themselves all the way around their circumference, and then ultimately making them slightly oversized to keep the tight fit. I could probably just print them in nylon and make them have an empty center and get the same effect, but over-torque could make them bend too much and slip. Perhaps a ring connected to a solid center by spiral arms...
</EDIT>
The challenge is coming up with one I can laser cut. A 3D printed version will be pretty simple.
I would also like to try to *lower* the gear reduction a little. 66:1 is a little excessive and prevents fast motion without really high speeds.
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Hey Daren, what about drawing inspiration from the kerf-bending approach? I did so for my strain wave gear designs, to try and emulate some of the give that a thin-walled steel cup would exhibit and assist the timing belt as it flexed.
https://i.imgur.com/EqIR3IU.png
https://i.imgur.com/lg8Eid6.png
You could do what I did around the circumference in a different orientation, such as in a line across the gear, but doing it concentrically made for consistent springiness around the whole rotation.
Should be totally laser-able.
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That's a pretty good idea.. I'm not sure it would work quite as well meshing with two rings, but I will give it a try for sure.
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A photo of a rough pencil sketch would be really helpful to understand the aim better - text is a tricky medium for this stuff! E.g. a sketch of the gear as a disc and lines to show where the split and forces are.
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@Simon Merrett What I was thinking was to make two planet gears, each half height so one interacts with the stationary ring, and the other with the output ring. Pin them in the middle so they stay concentric. Then make some way to generate a little constant rotational force between them, like using a pen spring inside a circular half-moon channel cut in both. It eliminates me needing to handle force across small areas joined only by layer lines in the 3D printed version and would ultimately be a lot stronger because of it.
Problem is that won't scale to smaller planets, which is something I'll need to make the sun bigger to reduce the ratio somewhat. Your version would scale better I think..
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