December 9, 2010

Rik's Egg Balance and Around the World

Rik's Egg Balance and Around the World are two more of the 2010 IPP Exchange puzzles I borrowed from George Bell. Rik's Egg Balanced was presented, designed, and made by Rik van Grol  at Buttonius Puzzles & Plastics. You probably know Rik from his publication Cubism for Fun, a booklet published three times a year with articles written about puzzles.

The goal of this puzzle is pretty classic: to get the egg to balance on its short end. This type of puzzle has been done a number of times and as Rob Stegmann notes, the U.S. Patent Office devotes an entire sub-class to "Balancing Ovoids" (ccl/273/154). This one is made out of plywood that has been laser cut and glued together.

Of course, you can't just stand it on its end by balancing it carefully. You need to first manipulate the puzzle in a certain way to get it to balance. You'll immediately notice that there are a few things rattling around in there. If you shake the hell out of it, you may end up with a ball bearing visible through the hole that the arrow points to (which goes all the way through the puzzle). It takes a bit more of a deliberate method in order to actually solve it though.

I think it took me about 5 minutes of rattling around before I solved it for the first time. What I didn't like about this one is that there wasn't an 'ah hah' moment, it was just some methodical manipulation until it worked. Perhaps there is a more clever way of solving it, but the way I found has only a moderate chance of success. Still, I can solve it in about a minute or two this way.

I tried this one out with my family to see how they found it, and most just rattled it around a bit before giving up. I think this type of puzzle is not as compelling as some other types because you don't really know what is going on. You have to make some educated guesses and go from there, which is how I figured it out.

Around the World is an assembly puzzle presented and designed by Kozy Kitajima. The illustrations on the pieces was done by Miwa Miwa.

This is another laser cut puzzle, but this one is made out of what appears to be fiberboard. The goal is to place the pieces so that the 8 pieces create a closed loop. Not all of them are shown in the photo.

Like a lot of puzzles of this type, I wasn't really sure where to start, so I just started messing around a bit hoping I would stumble upon the solution. However, when I got to the last few pieces I could see that it wasn't going to work out.

There is probably some logical way to figure this out, but I decided to try brute-forcing it by trying every possible combination of pieces. Fortunately, the pieces are numbered, so it was pretty easy to keep track of where I was. If you just look at all the possible permutations, there are 40,320, but since it is cyclical there are only 5,040 different distinct ways of arranging the pieces in a circle. This may seem like a lot, but sometimes you can tell that the first four pieces cannot produce a valid solution if there is no way to get back to the start.

I think I was about 1/7th of the way through the permutations in 30 minutes before I stumbled across a solution that worked. Phew! If that sounds like a lot of tedious work, it was! Assembly puzzles are not one of my favorite types, perhaps it is because I make them laborious by using techniques such as these. Any suggestions for a better approach?

Thanks again to George for loaning me all these puzzles! I've got about 6 left to write about, though two I haven't solved yet. I need to get cracking!

3 comments:

  1. This for sharing this puzzle, my kids would love this..am not a good player and really can't understand the logic!


    Mechanical Maintenance Engineer CV

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  2. For Around the World, I stacked the pieces keeping the notches aligned. I was then able to sort the pieces by "bending angle". In playing with the puzzle, it became clear to me that you don't want to put the pieces with largest bending angle together, nor the pieces with least bending angle together. So I tried various ways of mixing these two types and eventually stumbled on a solution. I'd be interested to see if it is the same solution you came up with.

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  3. CV, your comment looks like spam because of the link, but I guess what you said is fairly on-topic so I will let it stand.

    George, that is an interesting strategy! Probably more efficient than my approach (particularly if I had not gotten so lucky). Note to others: we compared solutions and it looked the same based on my recollection, though I'm not 100% sure.

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