This is a section of tread for a RC Nerf Tank I'm designing.

Sprocket Idler: http://www.thingiverse.com/thing:35909 Smaller Idler: http://www.thingiverse.com/thing:35950

These are being used on my RC Nerf Tank: http://www.thingiverse.com/thing:36305

These were printed on Tiny, my overly large 3d printer. Details and updates on my printer can be found on https://ottersoft.ca/blog

Print lots of these then use peices of 2mm wire bent up at either end to tie together. I also ran a drill bit through just to make sure the fit was a little loose.