Erik Demaine and Martin Demaine's Puzzles:

CSAIL Annual Meeting 2009 Puzzle

In what has become a regular event, Erik Demaine and Martin Demaine give out puzzles each year at our lab's Annual Meeting in June. Here is the 2009 edition.

While most of our puzzles are made from paper, this one must be made from rigid (flat) material. The official version is made from acrylic with a laser cutter, but we have made some in wood also. If you're working by hand, you could cut wood with a scroll jaw. Otherwise we would recommend a laser cutter (or water-jet cutter).

This puzzle is inspired by a similar (classic?) puzzle we first saw in Japan in summer 2008. We'd appreciate learning its full origin.

[150dpi] [300dpi] [EPS] [PDF] [AI] [DWG]


This puzzle is unusual: instead of taking it apart, your goal is to put it together. You are given two flat pieces and a ball. Your goal is to assemble them so that the ball is trapped in the central hole of both pieces, as shown:

rendering by Kenny Cheung

In an easier puzzle, you are given the pieces assembled, and your goal is to take them apart. This works well for thick material (especially wood) with the notches sized very close to the material thickness. But for thinner material this puzzle becomes a bit too easy.

Manufacturing Notes

If you're cutting by hand, try printing out the PDF file, pasting it onto a sheet of plywood, and cutting with a scroll saw. If you're cutting with a laser cutter, choose the vector format that your software can best handle (likely EPS or DWG), and set the color red to cut vector and the color cyan to score raster.

The files above are sized for material approximately 3mm thick. If you use any other thickness, you'll need to adjust the width of the two thin rectangles to approximately match the thickness of the material.

The files above are sized for a golf ball in the center. Golf balls can vary slightly in size, though. Any rigid ball (e.g., hollow plastic) would work well too, but you'll need to adjust the size of the central holes. We find the results are best when the hole is only slightly larger than the ball, so that the whole construction rests snugly when built.

Last updated June 27, 2014 by Erik Demaine.