[UPDATE 1: Sorry, I just realized, that I accidentally used 80034 ball bearings, not 624 ball bearings for this design. I'm already working on a updated, new, better, nicer and prettier design, using "real 624" ball bearings. I'll publish this new design on thingiverse shortly. For more information on this, see
http://pleasantsoftware.com/developer/3d/2010/04/22/the-power-of-reading/.]

[UPDATE 2: The new design is now available: http://www.thingiverse.com/thing:2473 ]

Ok, RustySpoon1121 beat me on this one ( http://www.thingiverse.com/thing:2318 ), but since my design is different (only 8 rollers, centrally mounted) and already finished anyway, I publish it as an alternative approach.

I use 624 80034 ball bearings to mount the 8 rollers on the center wheel.

For more information on the project (and more detailed build instructions), please see my blog post at
http://pleasantsoftware.com/developer/3d/2010/04/18/the-power-of-vacuum/

For one Mecanum wheel, you need to print:

• 1 center wheel (either a left "Felge-links.stl" or a right "Felge-rechts.stl")
• 8 holder parts ("Lager.stl")
• 16 half roller parts ("Rad.stl")
• 8x M4x60mm bolts (alternatively, 8x M4 threaded rod, each 60mm long)
• 8x M4 nuts (16x if you use threaded rods instead of bolts)
• 32x M4 washers
• 8x 624 80034 ball bearings
• 1x M3 nut
• 1x M3 bolt, e.g. 15mm or M3 set screw