Sometimes it’s not easy to decide which toys, tricks, or puzzles to include in these pages. Of course, any that are new to me seem appropriate, but a little research may reveal that they’re not as novel as I thought. A puzzle I’ve never seen may be dismissed as “old hat” by puzzle collectors; I may even discover that it was commercially marketed. A physics demonstration may cause a teacher to comment, “That one was discussed in one of the physics journals, oh, maybe 15 years ago,” with an implication that every teacher knows it, so it’s not worth discussion.

Magic tricks are often marketed, but seldom patented. Anyone who is a bit curious can find out the secrets of small tricks and large stage illusions with a trip to the library. When you start digging, you discover that very few of these things are new, and many have precedents going quite far back in history.

So I am resisting dismissive reactions from insiders. What’s common knowledge among experts is not necessarily known to the general public, and just might be of interest to quite a few MAKE readers; some may be inspired to make the devices I discuss here, or something like them, perhaps improving the idea in the process. The rest can skip this and move on to all the other good stuff in this magazine.

An Elegant Puzzle

Many puzzles are based only on geometry or topology. A few require a principle of physics for their solution, and these have a special appeal for me. I especially like puzzles that have everything out in the open, with no hidden mechanisms. Naturally I like puzzles that people have constructed with their own hands.

Here’s a beautiful puzzle shown to me by Mary Nienhuis, a retired high school mathematics teacher. It was made some years ago by Paul Hooker, then an industrial arts instructor at West Ottawa High School in Michigan.

The construction is of purpleheart and hard maple (it says so on the bottom), with a transparent lucite cover that allows you to see two marbles inside, separated by a wooden dowel. The marbles can move on curved ramps that have a depression partway up each slope. The object is to get both marbles to rest in those two depressions — simultaneously.Tilting or shaking the puzzle does no good. You can easily get one marble into its hole, but any attempt to get the other one in just dislodges the first one.

The Solution

Close examination reveals that the dowel in the center goes all the way through the maple piece and protrudes just a bit from the bottom. This provides a pivot so that the entire puzzle can be spun like a top, causing the marbles to rise up the ramps and

settle into their respective depressions. The puzzle must be constructed so that it is very well balanced about the pivot point.

This homemade puzzle is the cleanest and most elegant application of this principle that I’ve seen. So far as I know, this particular design has not been marketed. Anyone who enjoys woodworking can easily make one, or use the idea in other designs.

Quite a few classic puzzles employ spinning as part of their solution. Marketed “centrifugal” puzzles of this sort include the original Spoophem, patented by Fred Swithenbank in 1913 and released by R. Journet & Company in 1929; Moses’ Cradle by 1970s game maker Skor-Mor; and the S.S. Adams Co.’s Dipsy Ball. ThinkFun’s All Uphill is still available in a plastic version for just a few dollars.