Everyone,
I would like feedback regarding design and manufacturing options (in low quantities, and also in a "one-off") for a modernized reproduction of what is considered by many slide rule collectors (remember slide rules? ) to be the most precise and aesthetically-pleasing slide rule ever made: The "Gilson Atlas".
What makes the Gilson Atlas unique is its aesthetic simplicity yet relatively high-precision in a small package. For multiplication and division it yields 4-5 digits of precision (100-200 ppm), unlike common slide rules which give about 3-4 digits (>1000 ppm). It also keeps the digit precision more constant across the entire range of the scale, which is the bane of ordinary slide rules.
Unlike ordinary slide rules, however, it is not linear -- it is what is called a circular rule (strictly, the term "slide" should not be used in describing it.) The scale itself is helical-coiled, having either 25 or 30 spirals. Thus, even though the diameter of the Gilson Atlas is a little over 8", it packs a scale over 40 feet long, which is how it achieves its precision.
There are two nice online images of the Gilson Atlas. The first is the earliest Type I (with 30 spirals), while the second one (a very nice image) is the Type III (with 25 spirals) which was manufactured through the 1960's and maybe into the early 70's. The Type III was used by many professionals and students who wanted the higher precision it gave over an ordinary slide rule:
The Gilson Atlases were made from 1/16" coated aluminum. Note that the only moving parts are the two clear cursors (the backside used one cursor but I am focusing here on the high-precision side with the spiral scale.) There are no sliding scales as ordinary slide rules have. This adds to the aesthetic simplicity of the Gilson Atlas. For an overview of how the Gilson Atlas works, the original manual (for the 30-spiral Type I) is online at:
Wayne Harrison has produced a Postscript file of the scale layout for the Gilson Atlas Type III (25 spiral), which can be downloaded (along with an explanatory text file) from:
So what are the various design options in a modern replica of the Gilson Atlas? Here are my initial thoughts...
With regard to substrate materials we could consider:
1) Metal: aluminum alloy, titanium, stainless steel, etc. (anything which is corrosion/oxidation resistant). I think it should be a little thicker than the original 1/16" for added stiffness and "solid feel".2) Plastic: Obviously high quality is desired, having the ivory-like look and feel of the classic slide rules of old, such as Dietzgen, Keufel & Esser, etc. The plastic needs to be very stable (long- lasting and environmentally-resistant), scratch-resistant, able to resolve fine details of inscribed scales, and with the nice surface finish just mentioned.
3) (anything else ???)Then there's the issue of surface coatings (if any -- coatings can be painted/layered on, or in the case of metal could be electroplated, anodized, nitrided, etc.). And of course how the spiral and marks are placed on the surface with high precision and fineness (e.g., etched, scratched, painted/inked, etc., etc., etc.)
And lastly there's the issue of designing the rotating cursors.
I can't help but think that since the early 1970's (when slide rules were last king), new manufacturing materials and methods could be used to improve the quality and lower the manufacturing cost (including for small runs) for all types of slide rules. But then, maybe I'm wrong here.
Of course, there's no demand for slide rules for practical use, but there's certainly nostalgic interest (witness the large slide rule and vintage scientific instrument collecting communities), so I believe there is a small market there, maybe a few hundred to a thousand.
Your feedback is much appreciated. Let me know if you are interested in being involved with a project to design and build a circular rule similar to the Gilson Atlas.
Thanks!
Jon Noring
(p.s., it is intriguing to consider building a much larger Gilson Atlas, say for a science/technology museum, which can have an even more precise and longer scale. For example, one could etch the spiral and marker lines into a mirror polished stainless steel plate, say
3 to 6 feet diameter. The problem here is making the cursors stiff enough so they don't bend/bow sideways due to their own weight. And maybe there's a clever way to reduce the number of cursors to one and have an alternate method to register intermediate results.)