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Puzzle box

March 31, 2011

2 Min Read
Puzzle box

This episode of Gadget Freak comes, once again, from Instructables.  Over there I found a puzzle box, which is a clever locking box that doesn’t open unless you perform a certain gesture (with the box in your hand).  After that you can press a button and the box will open.

The trick involves a ball bearing trapped in a maze inside the box.  A magnet holds the ball in the starting position, and a small whack will set it free.  The correct series of gestures will move the ball through the maze, finally dropping it into a hole.  In the hole, it completes the unlatching mechanism that allows the button to release the catch that holds the lid shut.

The box is built up from layers of wood 4mm thick.  The maze has both vertical and horizontal paths, with the horizontal ones being cut out of individual plies and vertical ones being holes cut through multiple plies.  It also has multiple dead ends making it tricky to open even when you know the maze.  Since you can’t see the ball, if you fail to open the box on the first try you don’t really know what state the ball is in, and therefore how to get back to the starting point!

I was having trouble envisioning the release mechanism but the photo on step 5 makes it all clear.

The plies that make up the box were cut on a laser cutter, and the burned edges of the wood give a nice antique look to the project.  The author also etched the maze onto the inside of the box so that if it happens to be open, you can refresh your memory of what the maze is!


I can think of one change that would improve the box, or at least improve your chances of not being permanently locked out of it.  The change would be to add an additional ply to the box that implements an open cavity over the entire maze.  This would provide a simple way to bring the ball back to the starting point should you fail to solve the maze and end up with the ball in a dead end.  Just turn the box upside down, tilt towards the starting point, and turn right side up.

This also makes it easier to lock the box.  Currently you have to reverse the maze to bring the ball back to the start where it is held in place by the magnet.  With this modification the same upside down flip allows you to quickly return the ball to the start.

The Instructable includes cad drawings for the box the author made, plus scripts written in Python that allow you to produce cad drawings for other thicknesses of materials, and also to customize the maze.  Some of the comments indicate that the scripts aren’t trouble free, but the author appears very willing to lend a hand.

Steve Ravet

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