Penny Flip Puzzle

This is my spin on the Wooden Nickel Brain Teaser Puzzle produced by Creative Crafthouse. The design is simple - make slots for nine pennies in a row. I made the design more complicated by adding hardwood inlay on the sides and adding a built in compartment for the pennies when the game is being stored.

The object of the puzzle is to remove the coins from the board.

Setup:

• Place nine coins in the slots. The order of heads vs. tails should be random.

Rules:

• The person playing may flip any one coin before starting the game.

• You can only remove coins facing heads.

• Once a head facing coin is removed, you must flip the neighboring coins over. Note that blank spaces (gaps) do not count as neighbors.

• Keep removing heads and flipping neighbors.

• Can you remove all the coins?

The solution is given in the last step.

Tools:

• Table Saw
• Drill Press
• Forstner bit (3/4")
• Sander
• Wood Clamps
• Ruler
• Pencil

Materials:

• Wood: 10" x 2.5" x 3/4"
• Wood: 1/4" x 3/8" x 25"
• Wood Glue
• US Penny (x27)

You will be building to this drawing.

Cut 3/4" wood to 10" x 2.5" as shown. Note that I used a table saw for all cuts on this project.

Add the 3/4" pockets as shown. I used a Forstner bit and went down about 1/16 of an inch. The Forstner bit leaves a center hole that you may want to fill. Note that this picture is out of order (after inlay).

You might have noticed that the holes are shifted to one side. I wasn't sure how deep I was going to place the pockets when I started and wanted to make sure the center of my bit didn't break into the enclosure space. The other reason is that the open space allows for room to mark the instructions on the puzzle. I didn't have a stencil and my handwriting looks pretty bad. Therefore, my instructions are only verbal.

Cut the slots in the sides as shown. I made the cuts on three of the sides by setting the table saw blade height to 3/8" high and making a few passes from both sides. For the enclosure side, the blade was set to 1.25" high. Note that the pennies are 3/4" in diameter. Taking into account the inlay material, this leaves 1/8" of clearance through the slot.

Cut strips of material to 1/4" x 3/8". I used a scrap piece of dark hardwood (type unknown) to give a contrast to the pine base.

Glue the strips into the base on three of the sides. The forth side should be an interference fit (not glued) to provide access to the storage compartment.

A US penny is about 1/16" thick. You will need to be able to grab it so I glued together a stack of three. Ok, before you call the money police on me, I used water based glue that can easily be removed.

If you don't want to blow your $0.27 on pennies, you could make wood tokens to go in the slots. I thought about going that route to add color to the design. I would suggest taking a 1/4" thick (or thinner) piece of wood and painting the two sides - say red and blue. Next use a hole saw or punch to make 3/4" diameter slugs.

Place the coins in the slots. Use a random pattern and try to solve it for yourself. Can you remove all the coins?

Did you solve it? Try a few more times.

Notice that the puzzle has nine coins. Note how many are heads and how many are tails before you start.

Ok, here is the trick:

1. You must have an ODD number of heads facing UP. Note that the first step in the directions allowed you to flip one coin over.
2. You should start from the LEFT most HEAD coin and flip it.
3. Proceed by flipping the LEFT most HEAD coin.
4. If you follow this process, all coins should be removed from the board.

If the process isn't clear, watch the video in the next step.