On request, here's the current design of my printed Tricopter.I'm still working out some problems with the current design. It might have to do mostly with my terrible piloting skills, but the current Tricopter center plate get ripped in pieces much too easy. I never had that much problems with my Quadrocopter design ( http://www.thingiverse.com/thing:4812 ), which seems to be much sturdier. Of course, the Tricopter design is foldable, which means that the construction is a bit more complex. Also the Tricopter has a much larger diameter and is heavier than the Quadro, which might also cause problems with my (very) rough landings :-/The motor plates are designed for 2213N 800Kv Brushless motors http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=8622 but they probably work also with other motors.Use 10x10mm aluminum or wood profiles for the arms. I used 40cm long arms and 10" props.The servo is a BMS-385DMAX Digital Servo http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=8761I first used KKMulticopter controller electronics for the Tricopter (also visible on the photos below). Meanwhile, I switched to a MultiWii controller. Both work great, but the MultiWii controller also supports an accelerator chip (auto leveling), barometer and magnetometer...See the pictures in the following image gallery for more details on the assembly https://picasaweb.google.com/ZaggoPS/Tricopter?feat=directlinkYou'll need a 624 ball bearing a M4 x 20 mm bolt, some M4 washers, a M4 nut, 2 M3 bolts, washers and nylock nuts for the servo assembly.For more information on the snap-in hinge, please see section "2. Snap-in, not snap-off" in my "Two tricks" blog post at http://pleasantsoftware.com/developer/3d/2011/04/07/two-tricks/