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          The incredible Curta

    When I was a student there were these ads in Scientific American magazine, advertising a "miniature all-purpose calculator". I didn’t pay much attention then, and (alas) I didn’t think to buy one. By the time I did, their price had skyrocketed. I shouldn’t complain though… a Curta calculator is well worth any price!
    This is the ultimate mechanical pocket calculator; a true marvel of miniaturization and ingenious design. It does the same four arithmetical operations done by a pinwheel calculator like my Odhner; but the Odhner and its many clones weighed in at 6 kilograms or so, whereas the Curta sits comfortably in your hand, providing speed, convenience and precision in a mechanism weighing a mere 230 grams. It also sounds different: where the Odhner calculates with a good deal of noise, the Curta whirs as silently as the peppermill it resembles.
Curta Ad from Scientific American
Click photo to see entire ad
Curta Type I calculator
Click photo to enlarge
    The Curta was the brainchild of Curt Herzstark of Austria. He perfected its design while he was an inmate at the Buchenwald concentration camp, where he was assigned to work in a mechanical factory. The factory’s managers wanted to give the calculator to Hitler after the war is won, and so encouraged Herzstark to work on his design after hours. After V-day (thankfully, not the same V the Germans had envisioned) Herzstark eventually engaged a company in Liechtenstein and produced some 140,000 of his machines until electronics took over in the seventies. They were famously used in car rallies to execute the required gas and mileage calculations.
    The Curta uses the Stepped Drum mechanism invented by Leibniz in the seventeenth century, and later perfected to serve in many hefty desk calculators in the nineteenth and twentieth. Herzstark’s breakthrough was in using a single stepped drum for all the digits, with the digits’ readout gearing surrounding this drum in a circle, instead of the usual linear design that required a row of drums, one for each digit.
    The photos to the right show how one would go about calculating the product 123 X 456 on a Curta. You turn the clearing lever (the ring at the top) a full turn around the machine to clear the top readouts. You enter the 123 on the setting sliders (photo at left). Then you  turn the crank 6 times, move the carriage (the knurled top of the machine) a notch counter-clockwise, turn the crank 5 times, move the carriage another notch, and turn the Input setting levers and readout  Result and Counter readouts
Click a photo to enlarge
crank 4 times. The result of the calculation, 56088, shows in the result readout (black part of the top), and the multiplier (456) shows in the counter readout (white part of the top). This process takes under 10 seconds; in 20, you can do 1374214 X 49862 to get 68521058468.
    Curtas come in two models; mine is the Type I, supporting 8 digits in the input register (the set of sliders on the cylinder’s side) and 11 digits in the result register. The Type II has more digits, so it’s built into a fatter cylinder.

Exhibit provenance:
    An antique store, right here in Israel.

More info:
    - Interview with Curt Herzstark:
    - The Curta Calculator Page:

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