Reuleaux triangle
This week Angus on Makers Muse (1) presented a really interesting shape, that roles like a sphere but was a triangle, cool eh. This really messes with convention, so much so, you really need to try it for yourself.

We form the Reuleaux triangle by using three intersecting circular disks, each having their centre on the boundary of the other two(2). This produces a curve of constant width, normal we would think this should be a circle, but in this case its a triangle(3)!!! So, what can you do with this constant width triangle, well you can roll them between two flat surfaces like they were ball bearings... Take a look at Angus' link below, and have a go for yourself:-)

I would suggest printing at least three.

Definition of constant width is when two lines have the same Euclidean distance from each other.

Reference:-

1. MakersMuse YouTube - https://youtu.be/2eUWT9cI23o
2. Wikipedia - https://en.wikipedia.org/wiki/Reuleaux_triangle
3. Leonhard Euler - 1781- Paper on De curvis triangularibus.

I used Grey PLA from https://rigid.ink but you can use any colour you wish:-)