I posted about Reuleaux Triangles in 2017, and here’s another video about them. Like a circle, a Reuleaux Triangle is a shape with constant width. In other words, you can rotate a reuleaux triangle in a square with all four sides touching. In this video the Action Lab Man demonstrates Reuleaux Triangles and explains why they aren’t good as wheels – they don’t have a fixed center of rotation like a circle does.