The Calibron Twelve Block Puzzle (Updated 4/19/20)

This is a pretty well known story to the puzzler community but if you’ve never heard it before, here’s the condensed version: in 1932 Theodore Edison, youngest son of famous inventor Thomas Edison, created a puzzle of twelve rectangular blocks and named it, you guessed it, “The Calibron Twelve Block Puzzle”. Here’s what his instructions said:

“The problem is to arrange the twelve blocks to form a single large rectangle. Any rectangle, (including the square), will do, provided that all twelve blocks are used … There must be no gaps, overlappings, or projections, and no block is to be set on edge.”

So it’s a packing puzzle where figuring out the dimensions of the rectangular area to be filled is part of the puzzle. That may sound fairly tame but in fact it is a very hard puzzle – which I guess is not really that big a surprise given that Theodore earned a degree in physics from MIT and came up with over 80 inventions.

Although the puzzle came out over eight decades ago, not many copies have survived intact and figuring out the exact proportions of each of the twelve pieces has been a bit of a puzzle in itself. In 2016 for the Gathering for Gardner conference, George Miller and Nick Baxter wrote what I view as the definitive analysis. Based on new information and their analysis, I couldn’t resist trying my hand at making a reproduction:

It’s made from laser-cut acrylic and is 7″ x 5″. Here’s what the back looks like:

The original was made available in three versions. All three came packaged in the same rectangular box and all three held the same twelve puzzle pieces made from red bakelite. The only difference between them was the dimensions of an extra blue bakelite piece. The puzzle wasn’t sold in its solved state so the blue “spacer” piece was included to keep the red pieces sitting snugly inside the box. In my version I have included all three types of spacer pieces so that you can set your mind to solving multiple challenges, in ascending order of difficulty:

1. Getting the twelve red pieces and any one of the blue pieces into the rectangular frame. (OK, it’s true I’ve spoiled one of those challenges by showing the top picture but a) I bet you won’t remember it, and b) the original puzzle provided that information as well.)
2. Each blue piece allows a different way of packing the rectangular frame – and some are easier to find than others. So you have the added challenges of getting the twelve red pieces and a particular one of the blue pieces into the rectangular frame.
3. Mt. Everest: arranging the red pieces per Theodore’s original instructions without using any of the blue pieces.

I’ve made a handful of copies and put them up for sale on my Etsy store if you’d like to get a hold of one.

Anyhow, The Calibron 12 is a great puzzle with a great story behind it. There’s lots of information about it online and at least two reproductions (in addition to mine) are available for sale. Just a heads up, though: George Miller’s and Nick Baxter’s authoritative article includes pictures of solutions to all of the challenges above. Also, the Creative Crafthouse reproduction gives away a pretty major clue: the rectangle that outlines the solution. Pavel Curtis also makes a reproduction in acrylic and gives some additional interesting information about Theodore Edison. From the pictures (which may be out of date) on their websites, both the Creative Crafthouse and the Pavel Curtis versions appear to be using dimensions that differ from those given in the Miller and Baxter paper.

Happy puzzling!

 

July 30th, 2019 UPDATE:

Well, those went quicker than I expected and I am now sold out. If there’s enough interest I will make another batch so send me a message at eye-en-eff-oh at pyrigan dot see-oh-em if you think you want one. I haven’t figured out pricing for the next batch (it depends on how big the batch is) so I’m not expecting a commitment to buy, just an expression of interest.

 

October 13th, 2019 UPDATE:

Made a few more.

 

April 19th, 2020 UPDATE:

Made some more.