I made this derivative from JJShortcut's files ( http://www.thingiverse.com/thing:2415 ), but the original gears were giving me some grief, so after the second micro-servo broke I redesigned the thing with involuted gears. Operation should be much smoother now.

This is designed to be routed with a 1.5 mm straight cutter. Do not use tool diameter compensation on the gears, they have been rescaled and modified taking into account the tool radius. Do use tool diameter compensation on the other parts.

Use 6 M2x16 bolts to fasten the gears to the arms, the counterbored side of the gears holds the m2 screwcaps and should be placed against the plate, arms on the other side. Otherwise assembles just like previously described.