This step by step tutorial will show you how to print, cut out, fold, and construct a gear to get you started building your own papercraft mechanical devices. There is still some small problems with the design, but I'm trying to balance ease of construction with functionality.
You will need:
1. A Laser Cutter or X-Acto Knife.
2. A T-Pin, Straight Pin, or Push Pin at least 5/8" in depth, (regular pushpins are too short and map pins bend too easily).
3. Stiff paper, Brochures and Junkmail like Restaurant Menus are a good choice as long as they fit into whatever printer you're using.
4. A half hour of time and Patience, this is very much like miniature model building.
Step 1: Choose Your Size
There is a small, medium, large and extra large gear your can choose from for now.
I'm including 3 different file types to get people started. A zip file containing the parts in an EPS format for laser cutting, a copy of each one as a PNG file, and an illustrator template file (by popular request, I've also just added an archive with the files as SVGs, Inkscape away!). Remember that when you use the template file, all the objects are located in the symbol library, along with prefabs to help make your own constructions.
If you are going to cut it out with the laser cutter, skip to step 5.
I've found that the larger the gear, the less slippage you will have in the system overall, but it will take more time to construct a larger part. Here are your choices:
1. Small Gear
1/2 piece of paper
Teeth - 8
Inner Diameter - 60mm
2. Medium Gear
1 piece of paper
Teeth - 10
Inner Diameter - 75mm
3. Large Gear
1 piece of paper
Teeth - 12
Inner Diameter - 105mm
3. Extra Large Gear
2 pieces of paper
Teeth - 15
Inner Diameter - 330mm
Step 2: Print the Gear
Once you've selected and opened the gear you would like to get started with, print the file out on a stiff stock of paper and optionally tape it to your cutting surface.
Use junk mail or restaurant menus, anything lying around that is stiffer than normal computer paper and can fit in your printer.
Step 3: Score Folds
For any dotted lines on the image, I highly suggest scoring these with a ballpoint pen or any semi-blunt object you have lying around. After a little practice, I've been able to use the back of my X-Acto Knife to score my folds. This will make it much easier to construct the gear once you're done cutting.
Step 4: Make All the Cuts
Using the Exacto-Knife (with a decently sharp blade), cut any solid lines inside the gear first, then cut everything out of the cardstock. On the inside, make sure you pop out any of the inner tabs as they will be hard to get to after you start putting everything together.
You should now have both sides of the gear cut out, now lets get to construction!
Step 5: Connect the Caps
Fold the center tabs inward on the bottom piece and push them through the groove you cut on the top piece. Make sure that all the tabs are pointing straight up through the top piece and that the printed side is facing out for both caps.
Step 6: Fold in Teeth
Fold all the remaining scores on both sides. Push the tabs at the bottom through the top slots.
Make sure that the tab is on the inside, they should be held in place by the right angle they create, and the designed to also add structural support.
Step 7: Poke Holes
Use a thumbtack to poke a hole at the center pivots on either side. This is to ensure that the gear doesn't go off kilter when it begins to turn.
Repeat the steps and test it out on your wall surface or corkboard. These gears can stack on each other, so if you have a pin which is long enough, try making multi dimensional mechanical devices.