Farmer, Fox, Chicken, and Corn Puzzle

Farmer, Fox, Chicken, and Corn Puzzle

This is a remake of a fun puzzle that I grew up with as a child.

Here is the puzzle:

The farmer has a chicken, a fox and a basket of corn. He has to get them all across the river but he can only take one item at a time. See if you can have him do this without the chicken eating the corn or the fox eating the chicken while the farmer leaves them unattended. 

I built a physical puzzle (without using an Arduino or other microcontroller) that lets you 'move' each item with the farmer over the river by moving knife switches from one side of the 'river' to the other. If you make a wrong choice a red light turns on to let you know you have made a mistake.

Move the switch corresponding to the item as if you were moving the item. Move the farmer switch and the item switch he will carry over the river together, simultaneously.

You win if you get everyone across the river without the red light turning on.  

If you take a look on the internet you will find this same puzzle called by many different names.

One very informative Wikipedia entry called it the Wolf, Goat and Cabbage Problem:

The puzzle is one of a number of river crossing puzzles, where the object is to move a set of items across a river subject to various restrictions.

In the earliest known occurrence of this problem, in the medieval manuscript Propositiones ad Acuendos Juvenes, [from the 9th century] the three objects are a wolf, a goat, and a cabbage, but other cosmetic variations of the puzzle also exist, such as: wolf, sheep, and cabbage...

The puzzle has been found in the folklore of African-Americans, Cameroon, the Cape Verde Islands, Denmark, Ethiopia, Ghana, Italy, Romania, Russia, Scotland, the Sudan, Uganda, Zambia, and Zimbabwe.^[

An interesting aspect of this instructable is that the basic puzzle implementation uses no Arduino (microprocessor), transistors, relays or other high tech; just double pole, double throw (DPDT) knife switches, a battery, and light. The highest tech item in the puzzle is the LED which let's you know that you messed up and somebody ate something or someone.

There are other ways to build this puzzle, take for instance this extravagant version.

I enjoyed this puzzle as a child and am glad to pass it on to my family. I hope you enjoy it too.

Supplies:

• 4 - Double Pole Double Throw (DPDT) Knife Switches
• LED, Red 10mm Clear Diffused Lens (red lens shown)
• Wire, 22 AWG Stranded, Multicolor
• 8 - #6-32 Machine Screws
• 8 - #6-32 Machine Nuts
• 6 - #2 x 3/8 inch Brass Flat Head Phillips Wood Screws
• 4 - 1/2 inch Self-Adhesive Protective Bumpers
• 17 - Solder Lugs, 2.7mm
• 2 - Plywood, 3.5mm x 3 in x 14 in
• 2 - Select Pine 3/4 in x 2-1/2 in x 14 in
• Poplar 1/4 in x 3-1/2 in x 14 in
• Polyurethane Glue, Clear Gorilla Glue
• Wood Stain, Walnut
• Wood Stain/Sealer Semi-Transparent, 'Very Navy' blue

Not Shown:

• Battery Holder, for CR2032 Coin-cell
• CR2032 3V Lithium coin-cell battery
• 47 ohm resistor
• Heat shrink tubing
• Spackle or Wood Filler (Only needed if midlayer entry cut is visible)
• Black permanent marker or black paint

The design uses 4 DPDT knife switches and I wanted to have the switches arranged horizontally down the length of the puzzle which drives the layout. I also wanted to have the river recessed below the surface of the puzzle to mimic a river so I decided to construct the river portion of the puzzle from three layers; the River top layer to mount the switches to, a Mid-Layer that allowed space for the wire routing and battery, and finally a bottom cover. The three layer River portion has the Riverbanks glued to the sides.

Shown in the photo is the layout of the Mid-Layer with the hollow cut out section lined out along with switch locations.

The Mid-Layer includes a cut out hollow space that provides an area for the wiring, switch mounting hardware, LED and the battery.

I am lazy so I wanted to just use my bandsaw to cut out the opening (hollow) rather than drill a hole and use a coping saw. I placed the entry cut on the end so the thin side would be supported by a wedge the width of the blade kerf when the Riverbanks are glued in place. I just used some spackle to fill the gap since the end grain was intended to be painted. In hindsight I could have run the cut parallel to the river and then taken a 90 degree turn to have a vertical cut run into the Riverbank and the entry cut would have been completely hidden.

The second photo shows the Mid-Layer placed on the top River layer to which it will be glued. Also visible is the kerf wedge made from card stock that keeps the thin side in its original location as if no cut had been made.

Glue the Mid-Layer onto the plywood Top River Layer. I did clamp the side with the entry cut kerf to keep the thin side in place. I used gallon water bottles to 'clamp' the layers in place.

The Cover Piece covers the wiring compartment. I wanted end pieces as I did not want the cover piece to go all the way to the end edge. So two narrow cover layer end pieces were glued on each end of the Mid-Layer to make it so the wiring cover fit between them.

I trimmed the long sides of the center piece so the 3mm plywood River is the same width as the Mid-Layer. This was done in preparation for gluing the Riverbanks to each side of the center piece.

The Riverbank sides are glued to each side of the center piece. The Riverbanks extend past the center piece on each end so they can be trimmed flush later. I used wood clamps to press the assembly together. I also placed water bottles down onto the boards to keep them flat.

Mask the Riverbank sides and paint the River with semi-transparent stain/sealer tinted blue. I used a foam brush and did some scalloped 'waves' in the river paint.

With the center piece glued together with the Riverbanks the ends can be trimmed to even up the ends and make them all nice and flush. The trim cuts across the center piece (Mid-Layer, Top River and Bottom Cover End Pieces) and both Riverbanks on both sides so the end grain is all on one plane, flat and smooth.

I took the layout paper and folded it to fit between the Riverbanks. I then took an awl and marked the holes that needed to be drilled. All eight switch mounting holes as well as the 20 holes for wires to go to the switches. Remember there are three locations that have two wires going to them so these locations need two wire holes each.

Mask the sides of the River (the blue part ;-) and apply stain to both the top and bottom wood of the Puzzle. This step is pretty simple. Make sure to put down newspaper to catch drips.

Although the knife switches had screw terminals on the sides of the contacts I did not want to have the wires exposed. So I used the contact mounting screws on the underside of the switch to attached ring terminals for making the wire connections. It was helpful to write the name of the switch on the bottom as not all contacts are used on every switch.

I think this is the most difficult step. Connecting the switches together CORRECTLY.

I have provided a schematic with colors matching the wires shown in the assembled photo. I found it easier to attach lengths of wire to the switch that had the most connections, the Chicken. I then pulled those wires through the holes and ran the wires to the appropriate contact on the correct switch. I methodically followed the schematic I had created in order to make all the connections.

Each wire (or pair of wires) is soldered to the ring terminal under the correct contact.

When a switch had all connections made to it I used the machine screws, washers and nuts to mount the switch. Don't over tighten, I broke one switch mounting recess as the phenolic can be a bit brittle.

I had considered using a red plastic lens LED (as shown in the supplies photo), but opted for the diffused clear as I thought it was less obtrusive and kind of disappeared in the river. The LED can run directly off of the coin cell battery, but it's a lot of current to pull from the battery and the LED is blindingly bright. So in order to conserve power and to make the red LED pleasant to look at I added a 47 ohm resistor (color code: yellow, violet, black) in series with it. I soldered the connections and covered them with heat shrink tubing.

It's always a good idea to provide some type of heatsink between where you are soldering on an LED lead wire and the body of the LED. This can be clip-on heat sink designed for that purpose or just holding the lead wire with needle-nose pliers or clipping on an alligator clip. Either way it helps keep high soldering temperatures from getting to the actual LED silicon die inside.

The River layer is only 3.5mm thick and I didn't want the LED sticking up very far above the river, so I cut a piece of scrap plywood and drilled a hole in it and hot glued it over the LED mounting hole to make the wood thickness at the LED double the thickness. The LED sits pretty high up in the wiring compartment and just fits. It's so tight that I had to trim the heat shrink off of the LED wires next to the LED since they kept the Cover from laying flat.

I made tack solder connections to the battery holder pins and covered them with heat shrink tubing.

I used hot glue to mount the battery holder inside the wiring compartment between the Fox and Corn switches.

I cut a piece of 3.5mm thick plywood so that it fit in the opening around the Mid-Layer recess. I drilled 6 holes, three on each long side and then used a larger bit to create a countersink in the board. I fastened it in place with the brass screws and then stained it.

Note that the brass screws are so short and of such fine thread that they strip easily. I intend to get some brass inserts and epoxy them into the Mid-Layer and use some brass flat head machine screws to secure the access cover.

I wanted icons of the characters in the puzzle. I searched the internet to find the images you see. However, I could not find the basket of corn. I composited the basket of corn from a basket of apples and some individual corn ear images.

I cut the images out of vinyl on a Cricut machine. I think I may try to cut a stencil and spray paint the images onto the River Banks.

There are icons on both sides of the river so the puzzle can be played from either side.

The puzzled puzzler needs instructions. I printed the instructions below and fastened them to the bottom of the puzzle:

Farmer, Fox, Chicken, and Corn Puzzle

The farmer has a chicken, a fox and a basket of corn. He has to get them all across the river but he can only take one of them at a time. See if you can have him do this without the chicken eating the corn or the fox eating the chicken while the farmer is gone. Move the corresponding switch as if you were moving the item. You win if the red light does not come on and everyone has crossed the river.  

If the puzzle is played on a hard surface it's nice to not have it slipping all over the place so I placed some self-adhesive feet on the bottom corners. The whole game was a bit warped so I trimmed a bit off of one of the feet so it would not rock.

Now the puzzle is complete and it's your turn to solve the puzzle. Decide what item the Farmer is going to take to the other side of the river -- just make sure the chicken doesn't eat the corn and the fox doesn't eat the chicken.

Happy Puzzling!

Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler, Spoiler,

The Solution:

The Farmer takes the Chicken across the river. The Fox and Corn are left behind. The Foxes don't eat Corn.

The Farmer returns back over the river empty-handed leaving the Chicken behind.

The Farmer takes the Corn over the river. Leaving the Fox behind.

The Farmer leaves the Corn and returns back over the river with the Chicken.

The Farmer leaves the Chicken back on the original starting side of the river and takes the Fox over the river.

The Farmer leaves the Fox and Corn and returns over the river empty-handed. The Fox doesn't eat the Corn.

The Farmer takes the Chicken again over the river.

Everyone has now safety crossed the river!

The puzzle that has baffled inquisitive minds for literally centuries is now solved!

I hope you have many years of fun sharing this puzzle with family and friends.

Enjoy!