Daren SchwenkeSorted out the pitch changes needed to make #MPRT - Modified planetary robotics transmission mesh without interference. Two layers, two different gear pitches.
Added it.
I think I may still add a carrier for the planets as I actually do have room above them here to do so.
Here is what a pseudo cross section looks like.
The rim is printed with what is the up here, down. I actually needed that big conical shape to print this without needing supports. As a bonus, this puts the bearings right in the center as well.
I'm still debating if I want to add an o-ring to that gap between the motor ring gear and the rim. If I did, then I would actually have a sealed transmission here. That is a huge o-ring though and would definitely need to be lubricated if it was rubber, which may actually attract dirt more than just running it dry or using graphite lubricant. Then again, I could spring for some Teflon o-rings, or perhaps wrap the regular o-ring with Teflon tape? Actual sealed ring bearings of that diameter start at about 80 McDonalds cheeseburgers, so I won't be doing that.
I think I'll add the slot for the o-ring anyway, just so I have that as an option later. Sealed sounds pretty nice.
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Nice design, push the star gear through to the top layer, it will provide additional support for the top layer planets (the PD of the sun will be that of the top layer).
You can even add a roller bearing layers each side that supports the sun and planets, and locks the gears into place (magic!).
AlanX
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That cylindrical empty space above the sun is sized to contain two ball bearings which will support the wheel by riding on the motor shaft.
I had a nice 20mm shaft with a cross pin near the base, and a threaded end to work with here. So that works out to be: 6mm sun gear, 1mm space for bearing seat, two 6mm thick bearings, 1mm more for clearancing. and it's all retained by a 3mm bolt in the end.
The motors have really nice bearings as well, so I'm not worried about loading them.
I preemptively ordered the bearings for this, so they will be here Tuesday probably. :)
I was still thinking about adding a carrier for the planets which I can cut a ring out of the solid space above to hold it. I just really don't want to consume another 12 bearings though (4 wheels), so I'm going to try one without I think and see how it does.
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Actually I am in error. The design I was looking at used an idler in that space.
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