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In point of fact, I don’t think the particular rounded triangles built by Instructables user sherrycayheyhey to show off this unconventional Lego technique are quite convex enough to be proper Reuleaux triangles. But the general idea—exploiting the small play in each of a large number of individual joints and, to a small extent, the flexibility of the bricks themselves—could probably be used to make very close approximations. You’d just have to make each side longer by the right amount.

Sean Michael Ragan

I am descended from 5,000 generations of tool-using primates. Also, I went to college and stuff. I write for MAKE, serve as Technical Editor for MAKE magazine, and develop original DIY content for Make: Projects.



  1. kennedy2 says:

    Now THAT is a cool build!

  2. William Crawford says:

    If you made the sides longer, they would actually be less convex, not more.  The longer they are, the less each joint has to bend to make up for the square corners on the end of the triangle.  

    1. Interesting point.  Of course, if you make them too short, they may not be able to bend far enough at all.  Longer sides are at least capable of greater curvature, although you are absolutely correct that they will be under less tension and will not naturally assume a more convex shape. 

      1. I think.

        So, assuming that the sides of the triangles in the picture are at or near their practical limit of curvature, I think that, to build a triangle with more convex sides (e.g. a Reuleaux triangle), you’d have to A) make each side longer and B) apply some radial force, ideally inwards at each corner, to make them bulge out.

  3. Adam Brucker says:

    Check out Jeff Sanders’ work at for this idea taken to the extreme.

  4. oooooo pretty colorses. I wish I was smart enough to make them. Or had friends to help me. Forever alone.