Leib Stern’s slide rule

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Leib Stern’s slide rule

Specialty sliderule invented by Leib Stern for Turbocharger calculations

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    I did not have the pleasure of meeting Leib Stern, and had only become aware of his work when his daughter generously donated his slide rule to my collection.
    When I say "his slide rule", I don't mean it in the usual sense of "the slide rule he owned and used during his engineering work". Every engineer of his generation had one of those, of course. What I mean is "the slide rule he invented" -- an unusual distinction attained by few. And an even more unusual distinction is involved -- for this is "the slide rule he invented and then successfully made into a commercial product".
    Leib (Leonid) Stern was born in the Ukraine in 1914, and had a long career as a metallurgical engineer in the USSR. He immigrated to Israel in 1987, and had passed away here in 1999. He had the knack for innovation that marks the best engineers, and during his days as a metallurgist he had patented many inventions, including the slide rule shown here.

Here are scans of the front and back of this unusual instrument, which was manufactured in 1957 by the Leningrad measuring instruments factory. It is a specialty calculator, and most of its scales are unlike any I have seen before (all, in fact, except the two simple log scales that allow for multiplication and division). Being more of a VLSI and Electro-optics man myself, I wouldn't expect to understand the instruction manual even if I could read Russian; but a friend who can, figures it is dedicated to the calculation

Fabrication data in well of stator

of characteristics related to turbo-compressors and the air flowing in them -- pressure, efficiency, compression ratio, power, and so forth. In the days before computers, a slide rule was a big improvement over calculating by hand, but a specialized rule for one's specific profession and the common tasks it required was really precious, freeing time from drudgery for more valuable work (as I mention here).

Mr. Stern had thus done many engineers a favor by devising this slide rule; but unlike Western inventors, he could not go into business to produce it under his name. He was not even rewarded by having his name on the device -- only his initials, which can be seen here on the back among the parameter definitions and handy formulas. And yet, I can't imagine he wasn't pleased to come up with this work-saving improvement in the state of his art: an engineer can ask for no greater pleasure!

Mr. Stern's initials on the back of his slide rule

Inventor's initials on back of rule

		Exhibit provenance: I gratefully received this rule from its inventor's daughter. More info: A scan of a photocopy of the manual is here. If you can read it, please shed more light on this special slide rule's function and I will share it for other readers' benefit!