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          The Bare Bones Hemmi 22

    When I explain the slide rule to a curious soul, I say "and then William Oughtred had the idea that by taking two Gunter rules and sliding them next to each other, he could add the logarithms directly, without using the dividers". The problem used to be, when I took a slide rule to demonstrate, my listener would see in it three, not two, rules -- with as many as 25 scales... hardly a good demo. Actually, I had once seen a two stick slide rule. It was made in the 18th century, and cost more than my entire collection... so I was left to do my explanations with a standard slide rule and hope for the best.
    Until I got the Sun Hemmi No. 22. Unique among modern slide rules, this one has only two sticks and 4 scales -- truly a bare bones instrument.
Hemmi No. 22 - Front
Click photo to enlarge
Hemmi No. 22 - Back
    The no. 22 was made in Japan in the period 1954-1959, as a basic student rule that was apparently only sold in Asia. Its two main scales enable multiplication and division, with two additional scales for squares and reciprocals. No trig functions, no cubes, no frills. The slide (23 cm long) is held to the single stator by a metal bracket, and a very simple celluloid cursor completes the inexpensive construction, which you can see in the photos below.
Hemmi No. 22 - Components
Hemmi No. 22 - Detail  Hemmi No. 22 - Detail
    If you lecture about HOC, you're welcome to use this image, in which I photoshopped out the superfluous details to recreate Oughtred's innovative idea at its simplest and clearest.  Or you can make your own demo from this raw image.
1.5 x 2.8 demonstrated on a slide rule
Click photo to enlarge
Exhibit provenance:
    Paul Rossís Slide Rule Trading Company.

More info:
    Some sources claim that this model was made of Sandalwood. Perhaps... but the one I have certainly looks to be of bamboo.

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