I made some changes to Joakim's original parts, giving the wheels a hub and set-screw, as well as implementing small pressure pads to hold the roller shafts in place, instead of requiring glue. This allows the rollers to be changed in the event that one breaks. My set is printing at the moment, I'll get some finished product pictures when they finish! EDIT: For the first few people who downloaded this, I got the cores mixed up, but I fixed it now, so you should re-download.You will need 2 of each different kind of core for a simple 4-wheeled robot. Each core needs 11 rollers, and 11 pin clips, so for a full set of 4, that's 44 rollers, and 44 pin clips. You will also need some screws to fasten the pin clips, and the set screw. The shafts can be made out of pieces of 3mm printing filament, but since I don't have that on hand, I will need to think of something else. PROTIP: Although it'd probably fit on your bed, don't try and print all 44 pin clips at once. That's what I did, but it was the scenario of: 43 printed correctly on the first layer, but the last one didn't adhere... kill the print so it doesn't mess up other layers, then scrape off 43 perfectly good first-layer parts. I don't even have the energy to clean up the mess right now, those little bits fell like SNOW when I hit them with the putty knife.