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Some time ago I posted a notice that Sphere Research (seller of slide
rules, electronic components, and test equipment) was going out of
business at the end of 2024, following the death of its founder.

Update: "It seems we have more stuff than we thought. Disposing of all
the electronic equipment and parts will take at least until mid 2025. We
will be updating our web site regularly with new items for limited
times. The Slide Rule Universe will continue to operate for several more
years and we will update the web site with all the wonderful rules we have."

https://www.sphere.bc.ca/

I can vouch for their $40 Czech-made Logarex / KOH-I-NOOR 27401-X, a
rule with the "Reitz" 10-scale arrangement. The Sphere site says they
have "LOTS!" on hand. Mine arrived well packed in a box in perfect
condition.

For slide rule trig the Rietz system is a big step up from the nine
scales of the Mannheim rules. On the latter, the sin/cos scale S covers
0.5° - 90°, or two decades (0.01 - 1.0). On the other hand, the tangent
scales covers the single decade 5° - 45°. This is OK for simple trig,
but is exceedingly inconvenient if you have to multiply cos and tan as
in the Bygrave formulas.

The Rietz arrangement follows the method of all the more upscale rules.
The S scale is split into two scales covering a single decade each, so
sines, cosines, and tangents can interoperate easily.

--
Paul Hirose
sofajpl.com

   

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