Puzzles by George W. Hart

This puzzle is a 5-inch diameter spherical jig-saw based on a Goldberg polyhedron. I chose the (5,3) polyhedron, which has 492 faces, which is divisible by 12, so it can be divided into twelve congruent sets of faces.

These are its twelve parts. Each contains one pentagon surrounded by 40 hexagons. Because these parts are identical, it is not a difficult puzzle conceptually. But it is still fun to manually assemble. I was mostly testing the concept, to make sure everything stays together with friction alone.

Here they are again, this time in a stack, which is how I built them in the rapid prototyping machine.

And here's the puzzle with all but one piece put together. At this stage it is a bit tricky to get the final part in place because there is nothing to push against. I do it with the aid of a long bamboo skewer that I insert through holes in the other side.

If you would like to make your own copy of this puzzle, and you have acess to a 3D printing machine, the stl file to print is available here. Based on the success of this puzzle, I later made a more difficult variation on the concept with twelve different part shapes.