aeh5040 Posted February 17, 2014 Posted February 17, 2014 (edited) Here is by far my most ambitious project. It is a purely mechanical device which draws a fractal curve, driven by only one motor. So far as I know, this is the first time such a thing has ever been done in any medium, Lego or otherwise! Specifically, it draws a Heighway Dragon Curve, a space-filling curve that never crosses itself. It in fact draws a "twin dragon" which would in principle join up to form a loop, given enough time, floor space, and paper. (In practice, slight inaccuracies mean that it would not quite join up). I actually made this over a year ago (and it was the result of about a year of hard work), and showed it at BrickCon 2012. The long delay is partly due to the difficulty of filming it! The "brain" on the top layer consists of a series of Geneva mechanisms. These required many designs to get the motion smooth and precise enough - they also require a 45 degree offset. Each Geneva wheel is connected to two cams, one on the left side, and one on the right. The cams lift the two levers running along the sides in a particular sequence, related to Gray code (a variant of binary counting). When translated to left and right turns, this gives the Dragon Curve. The bottom layer contains two identical mechanisms controlling the two wheels, to enable precise turns. When one side is triggered by a cam, the wheel on that side needs to make exactly one turn. After many failed attempts, I was able to do achieve this using a variant of the "Tomy Armatron" mechanism (which was discussed here before), combined with a Scotch Yoke linkage. A worm drive ensures that the wheels are locked and cannot turn when not triggered. Enjoy! Here is what it would theoretically draw, after 256 turns, given enough space: Edited February 17, 2014 by aeh5040 Quote
JGW3000 Posted February 17, 2014 Posted February 17, 2014 I am totally flabbergasted; so intricately beautiful, clever and unique. Love the concept of a plotter machine running over paper, reminds me of HP plotters from the 1980's - you are using a similar type of pen. Would love to see building instructions or an lxf. What size paper are you using? Quote
Gilbert Despathens Posted February 17, 2014 Posted February 17, 2014 Wow, that's brilliant. Since I've never attempted anything like that, I'm curious - did you plan a machine that could draw the fractal and then find out how to build it with Lego, or did you start with the Lego and build the machine through a system of experiments? If the former was the case as I hesitantly suspect, which part of the process is more time-consuming - finding out how to draw the fractal, or making the Lego fit with the plan? Quote
legolijntje Posted February 17, 2014 Posted February 17, 2014 That looks cool. And it is amazing you made this 100% mechanical, no mindstorms at all. Great work! :thumbup: Quote
Mestari Posted February 17, 2014 Posted February 17, 2014 I was supposed to have my first post here on EB with my MOC but couldn't resist to start here by saying this is awesome! Mindstorms are great but real difficulty and challenge is in making it mechanical (and here with 1 motor only!). Congratulations :) Quote
Kumbbl Posted February 17, 2014 Posted February 17, 2014 For me a frontpage candidate and also a member of the new Technic Hall of Fame - Jim, what do you think? ;-) Quote
Philo Posted February 17, 2014 Posted February 17, 2014 Excellent! I was curious to see the relationship between Gray code and Heighway Dragon Curve, fortunately Wikipedia provides some enlightments... aeh5040, the string of Geneva wheels directly counts Gray code? Quote
TinkerBrick Posted February 17, 2014 Posted February 17, 2014 I just watched the video and i am amazed. Fantastic creation. The geneva wheel (or Maltese Cross) is brilliant. I wonder if it would be possible to "program" the device to draw other curves as well. This goes in the same category as PG52s Auto Spirograph. Instructions would be great . And yes. definitely a candidate for the Front Page and Hall of Fame! Quote
vmln8r Posted February 17, 2014 Posted February 17, 2014 This is excellent, and totally over my head. Great stuff! Quote
D3K Posted February 17, 2014 Posted February 17, 2014 This is amazing! Fantastic work! The only thing I don't like is the sound of the Lego motor Quote
robuko Posted February 17, 2014 Posted February 17, 2014 Maths is beautiful and this is excellent engineering. Love it. Quote
dhc6twinotter Posted February 17, 2014 Posted February 17, 2014 I saw this in person at BrickCon, and this thing is amazing. The amount of figuring that went into this is mind-boggling. Quote
Zerobricks Posted February 17, 2014 Posted February 17, 2014 This is top notch mechanical engineering... Just...crazy! Quote
Jeroen Ottens Posted February 17, 2014 Posted February 17, 2014 Wow, combining of two great hobbies in one masterpiece I remember programming these dragon curves in my youth, the merest possibility of the thought forming in my mind that this could be done with lego hadn't even started to materialize until I saw this video. Very well done. Quote
VKTechnic Posted February 17, 2014 Posted February 17, 2014 Wasn't this at BrickCon 2013? I remember seeing it there... Great work nonetheless! Quote
Blakbird Posted February 17, 2014 Posted February 17, 2014 I remember seeing this at BrickCon and talking to you a bit about it, but I don't think I fully appreciated what it does until now. It is hard to demonstrate without a lot of space! Quote
Splat Posted February 17, 2014 Posted February 17, 2014 Great creation you have there I'm always impressed by these types of mechanisms. Quote
captainmib Posted February 18, 2014 Posted February 18, 2014 How do you even start building something like this. Would be very interesting to read about the thought and building process. Awesome creation. I like mechanical stuff without dozens of pf or switches... Quote
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