3mm shaft vacuum turbine
This is basically the same thing as the one by RichMac without spacers and resized. I ported the files over to AlibreCAD, and resized it all for a 3mm shaft. I also made the rotors use hex insets, so 3mm locknuts provide the torque. This may not provide useful amounts of power, but it sure is effective in just making it spin. No spacers needed, just three or four 623 bearings two or four 3mm locknuts, and at least 35mm of 3mm socket cap screw - but that short and nothing sticks out. 50mm+ recommended.
http://www.youtube.com/watch?v=K5l5G1aihk
I had a smaller vacuum too so now it fits on a 28mm wide hose.