Introduction: Paper Resistor Calculator
Here is a small resistor calculator with three dials that you can make out of card stock paper. This version does not include the tolerance band, but if there's enough interest drop me a line and I may modify the design to include one.
Step 1: Papercraft Tools
For this project you'll need a few tools, namely a scissors, razor knife, straight edge and glue. Additionally I often use an old chopstick to help nudge the paper when necessary and to press down tabs. Also a "self healing" mat will save your tabletop but is not required.
Step 2: The Raw Materials
To make the resistor calculator, download and print the attached .pdf. Printing onto thick white card stock seems to give the best results. YMMV.
Step 3: Cut Out the Main Body
After printing out the .pdf cut out the individual pieces. I first cut out the main body of the resistor calculator, then cut out the black shapes. Afterward I gently score (with the dull end of the razor knife) the lines denoting the flaps and the dotted line showing where to fold the main body. This step makes it very easy to get nice crisp folds.
Step 4: Cut Out the Wheels
Cutting the wheels may be the most tedious part of this project. But making a "knurled" edge makes it easy to operate the calculator when it's all completed. I actually don't mind making all these cuts, but a sharp blade sure makes it easier. The technique I use is to first cut around the edges one way, then the opposite way freeing the wheel from the paper. Don't forget to cut out the center hole as well!
Step 5: Cut Out the Axles
Cut the axles out using a scissors. I tried using the razor knife but the edges weren't as smooth. Afterward cut the black lines shown in the picture then fold up slightly.
Step 6: Glue Axles
This step may be the most fussy, but I think I've come up with a way to insure sufficient accuracy. First, on the main body, poke a hole with the razor knife through each of the spots marked "a", "b" and "c". Similarly poke a hole through the center of an axle. While holding the tabs out of the way add a bit of glue to the back of an axle. Then, with the point of the razor knife through the hole you just created, mount the axle to the main body by aligning holes. You might want to experiment with the tab alignment in your calculator, but I've found the operation to work a bit more smoothly if the tabs are glued vertically with respect to the main body.
Step 7: Attach Wheels
The color wheels are now ready to be attached. Each wheel is coded with a letter a, b, c and should be attached to the corresponding axle. Attach the wheels in the order: a, c, b. This isn't critical but I think it helps the wheels spin easier. Check the back of the main body to see which axle is which. By bending the axle tabs up then slipping the wheel over each tab you can finesse the wheel onto the axle. I found that threading one tab at a time, with the second tab helped into place with the chopstick seemed to work pretty well. Go slow, you're almost done!
Step 8: Close It All Up
Finally, with a bit of glue on each tab, press tabs down and seal the main body shut. All you need is a very thin layer of glue -- hardly wet at all. Then use a chopstick (or similar) to press the tabs down. This pressure and tacky nature of your thinly applied glue layer will adhere almost immediately. If you've used too much glue keep applying pressure to squeeze out the excess glue. Try not to let any glue work its way inside the main body where it might bind up the wheels.
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