Three-Sided Cylinder Coins

Today we 3D printed some cylinder coins for students and classrooms to experiment with after watching Matt Parker’s video How thick is a three-sided coin:

These “fat coins” can land on their edges as well as their faces. Try out different thickness-to-diameter ratios and search for the fairest three-sided cylinder coin!


We made coins for five popular ratios with Tinkercad: the two ratios tried in the video, plus three inbetween:


We also made a parametrized version in OpenSCAD so you can try any ratio you like:

Screen Shot 2018-03-06 at 4.59.27 PM

If you don’t have access to a 3D printer, you can purchase 3D printed sets of coins from our Shapeways shop, in the same ratios as shown in the Tinkercad photo above, or as a set of 10 coins that range in ratio evenly between the 1:2*sqrt(2) and 1:sqrt(3) ratios shown in Matt Parker’s video. To save on per-part costs, the 3D printed coins print in a cage which you can break open after shipping:


Here’s what the 10 variable-ratio coins look like after removal from their cage:


Students, educators, and experimenters: if you want to get involved and add data to Matt Parker’s collection, check out Matt Parker’s follow-up video Help me find the thickness of a three-sided coin!..

Happy flipping!