Geared Code Wheel

This is an instructable on how to create a geared code wheel for your next treasure hunt or escape room. It basically consists of a piece of wood, a scavenged shaft from a copy machine, a series of gears from the same copy machine, two pieces of card stock like a file folder and a sharpie marker. You will need a drill bit the same size as the shaft, a fosner bit a bit larger than the gears that you have selected, a drill press for accurate hole drilling and whatever else you need to shape the wood to your desired form. The use of the code wheels is pretty straight forward. You have your encoded letter on the left and the decoded letter on the right. This setup gives you the ability to alter the code sequence by simply lifting one of the code wheels and rotating it then lowering it back down on the the gears. You can also code right to left, inner wheel to outer wheel and such. If you have enough gears lying around that are the same then you can make multiple sets of wheels and switch them out as needed. The picture above is before I put the indicator marker block on the base as I was being particularly evil and used a UV pen to mark the indicator arrows. A UV flashlight or black light was needed to be able to see the arrows and decipher the code. This is of course for adults so if you are making it for little ones a standard arrow will probably be better.

The whole of this project will depend on the gears that you can get. The type that you are looking for are flat, straight toothed gears about 1/4 inch thick. All the gears need to have the same pitch (tooth spacing and shape) so that they will all work together. You can use as many as you want but you will need at least 2 that are exactly the same for the wheels. This is so that they spin at the same rate and always come up with the same code/decode combination. If you have different gear ratios then on the first rotation you could have A=G and on the second rotation A now = K. Its also really handy if you have gears with a slightly larger shaft diameter. It is much easier to drill a 6mm hole accurately in wood then say 1mm. 6mm are common in most copy machines so that is what I used. I also managed to get two different sizes. Assuming that you are using the same gear type more or less than I am you will need a shaft for each gear. I cut my shafts about 1/2 long or about double the thickness of the gear. This made it easier to insert the shafts into the wood and get them out again if I needed to. Quick note on number of gears. If you use an even number of gears between the wheels, they will rotate in opposite directions. If you use an even number of gears then they will rotate in the same direction.

I made these on a alphabet to alphabet translation. You can make them how ever that you would like. Using a compass I drew two circles about 4 inches across. Since the needle of the compass made a little hole in the center finding the center was easy. I divided my circles into 32 sections. This will give you enough space for the entire alphabet and a few symbols like up, down, left and right. You can print out the above picture for an example. Set up one of the circles with the alphabet and any additional symbols you want. Make sure that every space is filled as it will be translated to something else on the other wheel. This will be the "read from" disk or the disk that shows the decoded version of the message. Make your second disk and then either mix up the alphabet or use symbols or whatever you would like your code to be. You can leave empty spaces on this disk if you want. Now that you have your disks lets make the gear section.

As you can see from the picture the base is just two pieces of 3/4 inch pine that has been glued together. A common 2x4 would also work if your gears are thin enough. You'll notice that the first and the fourth holes are empty. This is the where the wheel gears are placed. Those gears are glued to the back of the disks. Take your first disk that will be located on the left of the base and line it up so that the disk doesn't hang over the edges. with a sharp pencil make a mark where the center of the wheel is. In the picture the gears are countersunk into the board. We will get to that but first you need to drill the holes for the gear shafts then the counter sinking is done later. After drilling the first hole press a shaft lightly into the hole enough to be straight but not so far that you can't get it out. Set your second gear next to the first so that the teeth line up and are snug to the first gear. Make sure the teeth are tight together or the wheels will drift in and out of alignment. Drilll through the hole in the center of the second gear into the base. This will give you perfect alignment. Blow out the hole, press a shaft into the hole and set the gear over it. The two gears should mesh perfectly and spin without any slop between the teeth.Do this for the rest of the gears. Next step counter sinking the gears...

I did this part later so that I could choose the height of the gears. I used a forstner bit to make smooth flat bottomed holes that wont rub on the gears. You will need a bit that is about 1/8 larger than the gear that you are drilling for. If you have a drill press this is where you will it will be the most useful. After removing the shafts and the gears On the bottom of the drill bit there is a small tapered point. This must be as centered in the shaft hole as possible. Drill the hole just shy of the full thickness of the gear. You want a little to stick out the top so the the disk doesn't drag on the wood. The next gears that are not the disk gears are drilled full depth of the gear so they are flush or just a little below the surface of the wood. The second disk gear is only drilled about 3/4 of the depth of the gear. The second disk will be slightly higher than the first one so they don't drag on each other. The rest of the gears are drilled to just below flush like the others. Once all your holes are drilled, sand and apply any finish or decorations that you would like. Try to keep the finish thin and smooth in the gear area and avoid painting if you can.

While your finish is drying, attach the paper disks to the gears. Try to get them as centered as possible so when they turn you don't have a disk wobble...unless you want that. Hmmmm, that would be an interesting variation...may have to explore that some more. I used three very small drops of hot glue to attach the gears to the back of the disks. I figured that if I wanted to change the code I could simply pull the old disks off and attach new ones. After everything is dry on the base insert the shafts in the holes and one by one drop a gear over each shaft. You want to press the shaft so that it is just above the top of the gear in that pocket. If the hole is not deep enough then carefully redrill to give a bit more clearance.

to fully assemble, insert all the gears that are not disk gears. Insert the lower of the two disks. Here is the tricky part. Insert the final disk and note where code on the left gear lines up with letters on the right side. You will need to lift and rotate the disk to align the left and right disks to your "cypher combination". This is what makes this really cool. You can write a code with the left wheel A aligned to right wheel W. If you wish to "change the combination" simply realign the right wheel to a different letter and recode." By the way you can place your pointers for the left and right wheels anywhere you want around the edge of the wheels. Do the left one first, then center a letter on that pointer. The right wheel will follow it. Place the second pointer in the center of a letter on the right wheel and TaDaaah you are done. Happy coding

A Machine Tech