Hi Shapeways fans, Spinor Gears are a response to Bram Cohen's challenge when he saw my Fractional Gears, which features one gear with "half-fold" rotational symmetry. The question was whether it would be possible to design a gearing system with two identical half-fold gears, where the system returns to its starting state after 720 degrees of rotation, instead of the usual 360 degrees. The answer to the question is "no", as illustrated by the prototype. Even though the gears can rotate by more than 620 degrees, by far exceeding the 360-degrees mark, 720 degrees is not possible. The problem is that there will always be a "cross-over point", where there is ambiguity in which "track" the gear set is, and hence teeth bump into each other. Watch the YouTube video. Buy the puzzle at my Shapeways Shop. Read more at the Non-Twisty Puzzles Forum. Check out the photos below. Enjoy! Oskar