They are being welded over the weekend and we will get some up when we return to school on Tuesday. I am working on getting my students up to speed with a CAD file as well, but we only have 14 kids and only two of them have interest in CAD.
Basically picture a cheap ten inch tire like this
one
the other side of the hub has a extension that spaces out the pressed in bearings. We cut a 3/16" thick ring using our CNC plasma cutter that is being welded flush with the end of that hub extension. We will drill the proper holes and bolt the andymark sprockets from the kop to that ring.
A lot of posts have come up recently about these wheels and using spacers to make use of the 4 bolts that hold the hubs together. We looked at that option but didn't like the size required and cost associated with using a sprocket that would fit around those four holes.
Here is a really bad representation that I just threw together in Inventor