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Antique "Spirule" calculating device Spirule Walter R. Evans 1959 Instructions For Sale
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Antique "Spirule" calculating device Spirule Walter R. Evans 1959 Instructions:
$165.00
Rare Antique Spirule with instructions. "A plastic device consisting of a protractor and a pivoted arm with a logarithmic spiral, used to add angles between vectors and multiply magnitudes of vectors." The Spirule is made of clear sheet plastic, and consists of a disc that can rotate on a pivot in a wide rectangular ruler. Both pieces are covered with graphs, scales and other markings. The device is about 30 cm long. This device was the invention of the late Walter R. Evans, a brilliant electrical engineer who developed the "Root-Locus Method" for designing automatic control systems. He then invented the Spirule to help "nail down specific points on the locus - to establish the gain to use and the exact natural frequency and damping that will result". This device was manufactured by Evans's company in the 60's, and 100,000 of them were actually shipped before personal computers took over. Includes instructions. A true antique for the collector
Antique "Spirule" calculating device Spirule Walter R. Evans 1959 Instructions $165.00
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