If you think this looks like just another useless desk, toy, you are sooo wrong! It’s actually a sample to demonstrate  my plastic cutting capabilities. I was perusing Thingiverse looking for inspiration, and found this version, which at number 1082 appears to be a pretty early thing.

I liked the Reuleaux triangle because it incorporates some interesting geometrical concepts. Here’s a diagram to illustrate:

It just so happens that this shape rolls around nicely inside an appropriately sized square, as the following animated gif illustrates:

It’s a  principle which has actually been utilized to drill square holes. Click here to see the Wikipedia entry. Reuleaux, in spite of his French-sounding name, was actually a German engineer who did pioneering work in kinematics.

Here’s one last macro shot of my sample, showing the chamfer cut on the recesses where the nuts fit:

The nuts which fit in these recesses are 10-24 thread size, and are 3/8 of an inch across. Those toolmarks on the bottom are from an eighth inch diameter bit.

The plan is to put promotional engraving on these, check back for examples!