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Wooden "Burr" Puzzle

All > Other > Toys > Wooden "Burr" Puzzle by tsmaster

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A friend of mine had a birthday party recently with a "childhood" theme, including giving away gift bags to the guests, filled with candy and cheap toys. One of the toys in my bag was a plastic burr puzzle - the sort of puzzle where you pull out one piece, and all the other pieces fall apart in your hand, never to be reassembled, and one piece ends up in the couch, dooming your best intentions to figure it out anyway.

As this puzzle was designed for small people, I figured I'd be able to solve it quickly, and after a day or two of fiddling with it while watching television, I got frustrated and resorted to writing a Python program to analyze the puzzle and report solutions.

As it turns out, there are two independent solutions, after you remove rotations and reflections. The plastic pieces are definitely made to have an 'inside' face to them, and I was wondering if my program might find a solution where the inside faces were exposed, but it turns out that both solutions have all the inside faces concealed.

Giddy from finding a second solution (I don't recall which solution the puzzle was in initially), I wanted to make a larger version of the puzzle for larger hands. The original puzzle was maybe an inch in diameter, so playing with the puzzle was tricky for adult-sized fingers. I went to Home Depot and found 2x2s at 18" long, which seemed like a manageable dimension. I marked out the spaces to cut away and handed the cutting off to my father, who has a band saw.

The finished version isn't as snug as I'd like, so it falls apart if you don't handle it carefully. If I were to make another one, I'd cut more conservatively, and sand down to good puzzle-tolerance.

Later research into burr puzzles indicates that for a "two stick" burr puzzle, there are quite a few puzzles that have two solutions - the more interesting and rare puzzles are the ones with a single solution.

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The original plastic puzzle that inspired my puzzle.

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Two solutions of the plastic puzzle - note that the orange pieces are adjacent in the left solution, and not in the right solution, which means that these aren't just rotations of the same solution.

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The wooden pieces, unassembled - one of the things that had me chasing down a dead end was that the bottom two pieces are reflections of one another. I was convinced, incorrectly, that they needed to be paired up in the solution. Had I reexamined that assumption, I might have come up with a solution right away.

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Final puzzle, one step from completion.

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