Hi all, Just over a year ago I presented version 1 of this MOC. It is a purely mechanical device that draws a fractal curve - I believe it is the first time such a thing has ever been done, in Lego or otherwise. It uses a single L-motor, a series of Geneva mechanisms, and a stepped transmission mechanism to draw a Heighway twin-dragon, a space-filling curve that never intersects itself. (No Mindstorms here!) One problem with version 1 was that the final curve was huge - about 2m by 3m. Consequently I never found a big enough piece of paper and enough space to run it to completion - it just wasn't practical. In the new version I have managed to solve this problem. I filled the one remaining space with an add-subtract mechanism comprising two differentials. The previous version made a 90 degree turn by turning one wheel by a full turn while holding the other fixed. In the new version, one wheel makes 2/3 of a turn while the other makes 1/3 of a turn in the opposite direction. Consequently, the final drawing is 3 times smaller, about 0.7m by 1m. In addition, I redesigned almost every part of the mechanism, and made it far more robust and reliable. I think it is now at a stage where it would be reasonable of other people to make it - I am working on an LDraw file... The full drawing takes 256 turns and just over an hour to complete. It is accurate enough that the curve never intersects itself, and is within a few cm of joining up to itself at the end. Not bad for pure mechanical dead-reckoning! Here is the actual drawing, compared with a mathematically perfect computer generated version. More pictures and LDraw file on brickshelf and bricksafe