A 2x2x1 puzzle in about a day

The "Impractical Geometry" in a previous post was a visualization model for a puzzle that had been conjectured on a puzzle forum, here. Yesterday I was suddenly inspired by a practical, simple mechanism by which that particular puzzle could be built. When I came home, I threw together a model, exported it to Solido's SDView application, sent it to the printer, and let it build overnight.


I expected the parts would need additional work to make them practical, so I didn't bother with fillets and tolerances. I just wanted something I could look at while refining the model. They look nice, though.


The premise is that one part has a truncated spherical shell exposed on one side. The other three parts have spherical cavities that fit over the exposed shell and a spherical hook that reaches inside. I was surprised to discover how well they fit together.


With very little effort, all four parts snapped together and stayed together. It turns a bit like a truncated Rubik's cube. It's shown below halfway through a turn, and the parts move smoothly enough to confirm this mechanism is practical. Talk about instant gratification!