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Pins and Levers

Baldwin’s commercial pinwheel calculator

Other pinwheel calculator manufacturers had eclipsed Baldwin before he brought his own pinwheel calculator to market.

Pins and Levers

Frank Baldwin’s 1872 “pinwheel” calculator design was the first significant advance since the 1820 Thomas Arithmometer. Zero to nine teeth protruded from a thin “pinwheel” gear, depending on the position of a lever set by the operator. The number of protruding pins determined the digit entered by turning the gear. Additional gears in a row allowed multi-digit numbers. Other manufacturers copied Baldwin and eclipsed his tiny production.

Baldwin patent drawing

This was Baldwin’s first mechanism for changing the number of gear teeth to represent different numbers, but he did not market it aggressively.

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Odhner Calculator

Odhner machines were the first widely adopted “pinwheel” calculators.

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