Two years ago in school we studied Mayan and Aztec cultures and did an activity using paper "sacred rounds". They displayed the smaller Mayan year, Tzolk'in, and the two calendar pieces were shaped like gears; they turned in opposite directions, forming a 260-day year, created by one large 20 point gear and one smaller 13 recess gear. (As a comparison, the other, longer, Mayan year, Haab', had 365 days and so coincided with Tzolk'in every 52 years.) However, the small, simple "gears" we cut out of construction paper didn't mesh together, being thin paper, which made them frustrating to use, so I set out to recreate a larger scale version from wood.
Step 1: Step 1- Materials/tools
You will need:
-A sheet or two of 1/4 Inch plywood that you can cut out circles from (of the dimensions detailed in the next step)
-A large 5/8 Inch rectangular board- or whatever other shape you want, depending on your style preferences- on which to mount the gears
-A brass rod, approximately five inches long: I used 1/8 inch stock
-Two nuts that fit your die and brass rod
-Boiled linseed oil, tung oil, or Danish oil, etc.
-Any sort of Cyanoacrylate glue
-(Optional) A small wooden dowel
-(Optional) An old file/chisel handle, or any other dowel (Extra points if you turn it yourself)
-A screw die
-Sandpaper, a power sander or some sort, or files
-(Optional) A soldering iron/ torch and solder
-(Optional) A Japanese flush cut saw
Step 2: Scaling/drafting, Cutting the Rough Outline
First I measured the paper cutouts and scaled them up with a 6:1 ratio. This meant that each tooth of the large gear was one inch tall and each recess of the small gear was one inch deep. From the center point of my board I drew a circle with a large improvised string-pencil compass, with a radius of 6.5 Inches for the small one and 10.75 for the large one. I then marked out intervals for the teeth and the depth of the recesses, as well as the spaces between the teeth. I drilled the center hole in the size of my brass rod, cut the outer lines with a jigsaw to get the rough shape, and then measured where the pin holes would go on my mounting board.
I used a piece of Redwood I had on hand that had approximately the right dimensions for what I needed to mount the gears, but it did turn out that because the gears stuck out on all sides of the board it is pretty near impossible (or at least a damn nightmare) to store it on any side. This means that if you choose too small of a board, until it is mounted on a wall it must be stored flat on the ground- not great if other people in your house, be it your siblings, parents, or significant other, don't want large wooden gears on the floor.
Step 3: Touching Up
This was the longest step for me. If you were more careful in the cutting/ drilling than I was (I was a bit off center with my axle hole, which was a veritable nightmare to fix) this could be avoided, but I spent a long time touching up the teeth and making sure that the gears meshed correctly. Once I had the finish work about where I wanted it, I hit both the gears and the mount board with sandpaper, working up to about 600 grit. I then put on my first layer of oil. I used a total of six layers of oil, both linseed and tung, because I did not use a spar varnish, epoxy resin, or wax finish- purely hand-rubbed oil; however, any number of coats can be used at your discretion to achieve the look you want. Once two layers of oil were dry, I buffed it even more, to a 1000 grit fine polish.
Step 4: Detail Work
During this step I added a handle, which I sourced from an old file grip with a beat up ferrule; I pulled off the collar with pliers and knocked off the stepped end with a hacksaw. I then widened the tang slot with a drill and cut a piece of small wood dowel to fit in the hole, and a matching hole on the large gear. I drilled the hole in the center of an existing knot on the gear, but anywhere towards the outer edge would work. I then glued the dowel into the handle, and then into the hole in the gear, with CA glue (wood glue would work too). I cut the protruding end off with a Japanese flush cut saw and then sanded the area smooth.
During this step I also burned the 33 symbols/numbers into the gears and added a small compass rose-like design around each hole. This takes a long time to do by hand! Don't start with sore hands, because you will end up with them. I also added a directional arrow next to the handle, because, due to my bad cuts in the original rough cut, the gears turn better in one direction over the other. I added the next coats of oil after the burning.
Last, I glued the brass pins into place on the board, and tapped the spaces left above the gears once they were put on. I, however, ended up using a die that did not match any nuts at the hardware store, so I grabbed one I had lying around that fit alright and soldered it into place. I used a low-power blowtorch, and ended up with accidental burn marks around the pins that I actually liked a lot, so I added some more burn shading and lines.
And then I was done!