Cryptex 300 Combinations!

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Yes, even this design can be a free download once I am fully funded for my RoboGuts S.T.E.A.M. Education Program Kits; IF each viewer donates just $5 I'll be funded almost overnight and then all my designs become free downloads! The fastest and cheapest way to get all my .STL files free is to donate $5 to help fund school materials, once I have $3,500 I'll convert all these files to free downloads. https://www.gofundme.com/roboguts-kits-lessons Somebody asked for a Cryptex, so here's a simple Cryptex with only 300 combinations; I think the math is right for one ring; programming the combination is the little key tabs that slip into one of three positions for each of the five circular positions on a ring and there are five rings, with five choices each. N P K = n!/(n-k)! = (5!/(5-3)!) = 60 and with five rings = 300 combinations; so much confusion on the math I'll look into it more; just realized that if I use more rings easy modification to this kit just make it longer with more coding cylinders then it could be words or phrases standard size paper could result in over a dozen letters at this oversized design. If I spent a little more time on this all the rings could be the same width but this is enough to do the job and get the concept across. Alas, there's no place for acid in a glass to break; this is intended as a toy for children smart enough not to eat the programming keys. The storage cavity is 50mm x 100mm all these parts are MakerBotable too! If I had access to a MakerBot to actually build and test my creations that would help. This is another of many entries to the makezine.com/go/makerbot contest blog.makezine.com/archive/2010/04/makerbot_giveaway.html Instructions: MakerBot all the parts and figure out how to put the puzzle together! If you successfully make this with a 3D printer please send me the build-file and machine type so it can be uploaded here for others to use.