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Aspect Ratio Calculator
Article © MAIL User: Workshop Warlock

Aspect Ratio Calculator
I've developed a device, similar to a slide rule, for quickly calculating aspect ratios. It can deal with wire sizes from AWG 30, SWG 33, or 0.010" to AWG 3, SWG 4, or 0.25", and aspect ratios from 2 to 50.
Making the Calculator
Download this graphics file (36kB).
Print the file at 300 DPI and it should fit on a normal 8½x11 sheet of typing paper. Completed, it's 3x5.

  1. Cut it out
  2. Cut out the two windows
  3. Fold along the lines
  4. Tape the back if you want
  5. Slide the smaller piece into the bigger piece (you may need to trim it)
  6. You're done.

Using the Calculator
The calculator looks like this:

Image: calculator1.gif

From the top to bottom, the scales are:

The scales on the slide are not shown to avoid confusion.
To calculate aspect ratio, simply find the ring ID on the sliding scale in the top window or the top half of the bottom window, and slide it until it is lined up with the AWG, SWG, or wire diameter of the wire you're using. For example, if you're using 28 AWG wire on a 1/4" mandrel, you'd line up the 0.25 on the slide with the 28 on the AWG scale.

Image: calculator2.gif

Without moving anything, read the number off the slide across from the arrow on the AR scale at the bottom: just under 20.

Image: calculator3.gif

This ring has a very high aspect ratio!
Another example: 18 SWG wire on a 1/4" mandrel. Align the 0.25 on the slide with 18 on the SWG scale and read about* 5¼ opposite the arrow on the AR at the bottom.
Another example: 0.05" diameter wire on a 3/8" (0.375") mandrel. Align the 0.375 on the slide with the 0.05 on the in/mm scale, and read 7.6 off the bottom.
Another example: 1mm wire on a 10mm mandrel. To make the metric sizes fit the scale, divide each by ten in your head - 0.1 and 1. Align the 1 on the slide with the 0.1 on the in/mm scale and read 10 off the bottom.
Starting with the AR and finding the wire size: just align the AR you want with the arrow on the bottom, and aligned with the mandrel size is the wire size - read any of the three scales, inches, SWG, or AWG. You don't need to move the slide to consider another mandrel size either - aligned with all mandrel sizes are the appropriate wire sizes! Likewise, across from all wire sizes are the appropriate mandrel sizes! Just pick off whatever combination you like best. For example, if you're making Jens Pind (who is Jen, and does she know we have her Pind?) you can just align the AR arrow with 3, and read off all the appropriate mandrel and wire size combinations.
AWG, SWG, and inches (but not metric) are lined up so that equivalent measures are all in a straight line. That is, AWG 24 and SWG 25 are the same diameter, and are directly aligned with each other, as well as 0.020" (use any convenient line on the slide as a pointer to help you line them up.) This lets you convert AWG to SWG to inches, or whatever.
I hope you all find this useful.

* Slide rules are very accurate, but not very precise.
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