This was based on Eccentric Sphere Gears (http://www.thingiverse.com/thing:6499). I modified the SCAD files so that it would use pins instead of screws to secure the gears to the center piece and instead of a sphere a tetrahedron is used. Also, this one is not eccentric so that the gears spin without the object dramatically changing shape.

I have included the SCAD files for the gears (tetra.scad) and the pins (pins.scad). Note in the gears file - the function eightflatgears() shows all components laying on the same print plane - and eightgears() shows the item assembled minus the center.

Gears