Treads to try out my own TPU filament... worked great :-) For this proof of principle design I used long M6-threaded screws (the hubs/wheels were screwed onto them) and ball bearings. The fuselage is not in any way a good design, only a fast base to test the hubs/wheels/tread... the drive-wheel was fitted directly onto the geared-motor axis. Different flexible filament would perhaps work, make sure its not too stretchy since it might not stay on the wheels/hubs. I used my own: http://www.creativetools.se/pi-etpu-95-250-carbon-black-1kg-se It has only 250% stretch and also 95 Shore A. It is also conductive and if you make both the hubs and thread in this material you will be able to handle the static electricity that is built up when plastic moves... Follow me on Instagram and twitter: http://instagram.com/rubber3dprinting https://twitter.com/rubber3dprint http://rubber3dprinting.com/ http://www.palmiga.com http://youtu.be/5eNIRqblpPA http://youtu.be/Hq7a0xfTBuk https://www.youtube.com/watch?v=O9NCSGdXK8U