My Little 3-Card Burr Saga

Quite a while ago now I was sent a copy of George Miller's 3-Card Burr as a gift from Wil Strijbos. I had an idea of how it went together as I had seen a few copies in other people's collections in the past, however I also knew that it had a rather interesting quirk to it. Once the puzzle has been assembled into it's final burr state it will not be able to come apart again without the cards being destroyed in the process.

Scott Elliott phrased the process involved much more eloquently than I would've in a comment on his blog, so I'll just add it here:

"The one-way feature elegantly balances topology against the limitations of the cards' material properties. You must put the cards under a great deal of stress to assemble the puzzle, but the cards work together to keep that stress under control until you reach a fully-assembled equilibrium. Once it's assembled you can't go back because neighboring cards resist the movement instead of assisting it; the force required to overcome the resistance would exceed the material strength of the cards."

I was worried that there could be a real chance that I could screw up the assembly of this puzzle, and as such destroy it completely. So with this in mind I did something which even I consider to be very sad; I decided to keep the puzzle unsolved until I worked up the courage to put it together.

3-Card Burr DIY Attempt

Because I really wanted to know if I could assemble the puzzle, I asked fellow blogger Allard if he would mind sending me a rough diagram of the cuts needed  so that I could make a copy for myself that I wouldn't mind if I screwed up a few times. He kindly obliged and thus my DIY attempt at the 3-Card Burr was born!
It was made from a cheap set of plastic playing cards that I had lying around. All it took was a few vague guessed at measurements, some pen lines and a scalpel and the job was done. The fit -to put it nicely- is not amazing, but it does work! And for me that was the main thing.

Quite some time passed from this point, and I was content that I had sort of solved this puzzle with my DIY attempt, and this negated the fact that I owned a perfectly solvable puzzle that was still in it's original packaging. During this time I was entering into a rather unusual puzzle exchange with Scott Elliott for a copy of a puzzle that he owned but wasn't particularly attached to (more on that later).

Now I say that this was a rather unusual puzzle exchange because neither myself nor Scott had properly exchanged a puzzle before, so this was new territory for both of us. Somewhere along the line I had mentioned to Scott that I owned an unsolved copy of the 3-Card Burr, and he saw this for the shame that it was. So to add an interesting twist to our puzzle exchange he imposed an 'unconventional stipulation' on my 3-Card Burr. As part of this exchange I was required to properly assemble my copy of this puzzle!

3-Card Burr PVC Practice Copies

Although Scott had put forward this unconventional stipulation, he is not a cruel person. To compensate for this unusual condition (not that he had to of course) he very kindly said that he would send me a couple of PVC samples to practise on that he would make up using his awesome 3D printer. These PVC copies could stand a little bit more force than the card version, so they would be perfect for me to practice on before putting together the real thing. I put these together using the same method I applied to my DIY version, and they went together no problem. I even took them apart again, which is something that cannot be done with the card version, showing that there is indeed more 'give' in the PVC.

Now that the warm up was complete I had no real excuse to hold back any more. I unwrapped George Miller's 3-Card Burr from it's shrink wrap packet and proceeded to put it together.

George Miller's 3-Card Burr

I had a bit of a scare during the assembly process when one of the cards got caught up and had begun to bend a little bit too much, but luckily this was easily corrected with a bit of gentle prying. The tolerances were so tight that I have no problem believing that this puzzle will never be able to come apart again, but now that I have it together I'm not bothered by that in the slightest.

Scott was right, you really do have to put this together and see it for yourself to really appreciate it, and I'm actually very glad that he decided to bring this unconventional stipulation into our already unconventional puzzle exchange.

And here they all are together, my little 3-Card Burr family:

My 3-Card Burr Family

A big thanks to Scott for pushing me into eventually doing the right thing. And also to Allard for his help in making my DIY attempt possible.