Okay, I skipped the Blender software.. too complicated to learn quickly
Above is part of the tracked wheel system designed in Alibre, didn't take me long to do it. If you have learnt CAD software before, Alibre is relatively easy to understand. You can download it for free
HERE, but you'll need to register first. Its a 30 day trial of the full software before it disables some features (like assembly). I think theres a register-free edition
here.. am downloading it now to check it out.
I think I need some more time to learn the Blender software.. its not really a CAD software, rather a modeller and animator of some kinda. But you can get really awesome looking outputs with it!