You must have seen the domputer: https://www.youtube.com/watch?v=OpLU__bhu2w. All it needs is a huge number of dominoes. A few years ago I built the PAPAC-00, a "2-register, 1-bit, fixed-instruction binary digital computer", out of card and pins. It was very fiddly and not at all tolerant of errors in the cutting-out. I first saw it at http://longstreet.typepad.com/books/2010/11/item-mayer-rollin-p-papac-00-a-d..., though there's another reproduction in "IRE Transactions on Electronic Computers" at http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=5222708. Papy's Minicomputer is a very exploding dots-ish idea: it's a square board divided into 4, and you "calculate" by moving counters around - a counter on the 2s square is worth two counters on the 1s square, and so on. Frédérique Papy wrote a paper about it: http://www.rkennes.be/Papy-Minicomputer/minicomp-anglais.pdf I note that while gmail was spamming math-fun emails for me, someone else pointed you to Chalcraft and Greene's train sets paper (and on my site, no less! I never expected it to actually be *useful*!) On Tue, 21 Mar 2017 at 14:33 James Propp <jamespropp@gmail.com> wrote: In conjunction with the Global Math Project, I'm putting together a list of videos showing interesting forms of binary calculation, using water in cups, trains on tracks, etc.: http://mathenchant.org/binary.html I'm aware that the categorization of the links is a bit inconsistent; I plan to fix that before I publicize the webpage broadly. For now I'm mostly looking for more interesting links, and I figure that some of you will know about things I'm unaware of. I also am chasing the idea (mirage?) of a robust, cheap, easy-to-build binary calculator that could be taken on as an in-class project by students around the world. (Call it the mathematical equivalent of the penny-a-shot rotavirus vaccine.) I have no idea how to build such a thing, but maybe some really clever person has already figured it out. Thanks, Jim Propp _______________________________________________ math-fun mailing list math-fun@mailman.xmission.com https://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun