by hka, published
This is a wheel that is able to drive in all direction in a plane without having to turn (with som limitations). The idea for the design isn't mine, I stumbled across this [ http://www.youtube.com/watch?v=BTp2UAaihaI ] video a couple of years ago and thought, I want one of those!
And now I have a 3d printer. I've made a model in openscad and printed a version of it that seems to work to some extent. I wanted to make it all printable but was unable to manage the gears (I'll have to spend some more time on them as of now I use some I got of ebay ( http://www.ebay.com/itm/BEVEL-GEARS-PAIR-2mm-BORE-12mm-DIAMETER-BLACK-NYLON-66-/290844724436 )), the bearings was another part I were unable to print. I tried making a bearing using cylinders instead of printed balls but it didn't work well (seen some designs here using BBs I want to try though).
The problems I've thought of this far are mostly ones concerning how to drive the wheel and control the motion. As long as you only turn the thick axis (the one that makes it turn around the y-axis in the picture) there isn't really any problems. The thing that is hard to control is the behaviour when you turn the thin axis (which makes it turn aroun the z-axis). This motion depends on how the other axis is turn.
I will update this when I have time to work on it. Hopefully I'll get a working design and some control circuit for it.
The none printed parts I used were a pair of bevel gears, these should not be more than 12mm in diameter unless some changes are made to the scad file.
I used two 608zz for bearings, some more bearings might be nice when actually mounting it to something.
As inner axel I used a straw I had laying around, it might be possible to print but is quite long and thin.
For buildning one ball you need to print two of "halfsphere.stl" and one of each other stl. And you also need the pair of bearings and gears.
I'd be happy for any suggestions for improvements of the design, I've seen some printed tank treads here on thingiverse, if someone has an idea how to make one that fits these balls I'd be very happy.
The openscad file is a bit messy but should be possible to navigate atleast. different views and how to separate the parts are at the bottom, and some notes about the different parts.