The above linked instructable is awesome. It's cool, and the joints it uses (holes drilled in box tube) will egg out very quickly and degrade with time.
So, I decided to beef it up, so mine wouldn't end up crippled. I followed the instructable pretty well, but used different motor mount configuration, used the wheelchair's motor controller, and made my eccentric drive plate out of steel (free) instead of aluminum.
The theory in my telescoping sleeve bearings is that there is strong steel in the middle (bolt), and less strong steel on the outside (pipe/box tube), with brass and grease inbetween. This brass/grease will decrease wear on the steel components, and take up the slop.
This is a work in progress, to be updated as progress comes along.
Step 1: Measure Your Bolts.
Your top end bolts will probably be smaller, I used 3/8th up top, and 1/2 for main drive.
Step 2: Get Some Pipes!
i got lucky with my top end, and have 3/8th bolts, with 13/32nd or 27/64th inch brass tube, and a 1/2 inch OD steel tube that fit really well. At this point of buying things, go around with your bolts, and just try different combinations to see if you can get lucky. If you don't get lucky... Well then.
I didn't get lucky with the main drive. I got the 1/2 inch bolts, I found some weldable steel pipe with supposedly 1/2 inch ID, (which was a good bit larger, around 1/8th or 3/16th larger), and then got some brass pipe with a 31/64 ID, and a large OD. Measure accurately with some calipers, chuck that brass on the lathe, and go to town.
Step 3: Drill/overbore the Holes, Insert Pipe, Weld.
Wash everything, then weld away. I TIG'ed everything, because the tolerances were tight, and I wanted it to be strong. A very good welder could use MIG... I don't think I could. If you don't have tig, perhaps gas welding or stick would be the next best? It comes down to you wanting a good weld with minimal excess fill sticking up top to grind off, then sand it smooth so it doesn't interfere with the washers.
If you get much metal slumping inside the pipes, you may need to bore out the holes. If so, i'm sorry, because that will suck. Just use a lot of cutting fluid.
Step 4: Add Offset
Step 5: Make the Brass Inserts.
This is somewhat of the moment of truth. As it turns out, truth wasn't good for me. My 31/64th id (.485ish) didn't jive well with the .480 bolts, so I lubed them up, and pressed them together with a vice. All the wear is going to be on the outside, apparently.
Step 6: Get a Lift.
Step 7: Nylock Is for Suckers.
Also, don't be like the original hexabot dude. Put your bolts from the outside in, so that you have minimal clearance past the legs themselves. The caveat is the center bolt, which must be facing out. I'm thinking about chopping, drilling, and safety wiring that one.
Step 8: Assemble, Refactor, Rework.
Current theory is to re-use the banks (8 per motor) of IRF3205 MOSFET's to change a