Tetrahedral Roller Car

This `tumble proof' vehicle is ideal for rough terrain. Designed simply by adding four ball bearings to a tetrahedron yields this new vehicle design. No matter how this vehicle falls, it can still travel along the ground.
`copy_of_tetbaball3.stl' is the simple version. The other version has added spikes etc. that hold the ball bearings still, and can be broken off after 3D printing (this is more reliable, but requires cleaning after printing).
Youtube video:
https://www.youtube.com/watch?v=Xr4J9NCTPvA&index=3&list=PLCTMeyjMKRkrhMSOf0SD677liIG6aaZ_3
My Shapeways shop:
http://www.shapeways.com/shops/croco
My website:
https://sites.google.com/site/richardsouthwell254/home