Sunday 16 September 2012

IPP32 Exchange Puzzle From Wil Strijbos

Update 26 October 2017 - Dear Reader, please check out my new puzzle blog and e-store at

Wil Strijbos calls his Exchange Puzzle at IPP32 the "Exchange Washington DC". A bit of a mouthful here so I will just term it "The Exchange".

Wil's Exchange can be classified as an "Impossible Object". One look at the puzzle and you can see why. The Exchange is made up of a 60 ml urine sample container, within which there is a lock with key inserted, both suspended at the end of a red plastic rod that runs through the container's cap. Residing at the bottom of the container is a steel ball bearing. The bottom of the container has a cut-out hole, but not large enough for the ball bearing to pass through.

At the top end of the red rod is a screwed-in loop which hangs another key and a rectangular-shaped ring. A rubber bung helps to hold the rod in place and prevents any unnecessary sliding down. The cap has an unbroken seal so you probably wonder how Wil had managed to squeeze the lock and the other contents into the container.

The object of the Exchange is to remove the ball bearing and have the final puzzle looking exactly like the "Solution Picture" (see above photo). There is an additional challenge which is shown on the reverse of the photo below-to get the rectangular ring over the shackle of the lock inside the container.

Solving impossible objects requires logical thinking and a systematic approach. For this one, a fair amount of dexterity is also required. I discarded my usual trial and error method and actually spent some time analysing how to extract the ball bearing.

There are twelve steps to solving the puzzle as intended, at least according to my count. Without giving too much away, firstly there is no need to use force; the laws of physics cannot be defied. Secondly, do not attempt to break the seal and unscrew the cap (I don't think Wil intended it to be solved this way). Lastly, everything you need to solve the puzzle is there and no external tools are required. You just need to think creatively how to use what's been given (in a way, you can think of this like a sequential discovery type puzzle)....and if you happen to have nimble figures, this would certainly help as well.

This is my first impossible object from Wil (who has produced a number of Coke and other bottle creations in the past). I found the Exchange very enjoyable and while the removal of the ball bearing itself is not too difficult, it is the getting everything back into position that is more challenging. For a while I was caught off guard; the way forward for the last two steps was right in front of me...yet I just didn't see it.

What I like about the Exchange is that you can see everything that you are doing - no hidden this or that. Definitely worth getting  for both the fun factor and puzzling aspect. As of this post, I am still puzzling over the second challenge which seems to be a real tough cookie!

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