Hi Shapeways fans, Double Fractional Gears is a spin-off of my Fractional Gears. Whereas the latter features a gear with "half-fold symmetry", this gear system also features a gear with "third-fold symmetry". That gear needs to complete three full turns (1080 degrees) for the gear system to get back to its starting position. So the gear system as a whole has a half:third gearing ratio at average. It was quite a challenge to develop this gear system, with six virtual prototypes and two 3D-printed ones. The biggest problem was to prevent the gears from bumping into each other. The gear-on-gear approach of Fractional Gears did not work. The working solution was to have the teeth spiral around their axle two or three times. 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