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The Webb Adder, 1889 form

This form of the adder was patented by C.H. Webb on Nov 5 and Nov 12, 1889. Webb's first patent for the two wheel adder was granted 21 years earlier, in 1868. The heavy body is of nickel plated cast iron, with nickel plated steel plates, the larger one with 100 divisions, from 0-99, and the smaller with 50 divisions, from 0-49. One revolution of the large wheel causes the smaller wheel to move 1/50th of a revolution. A quite heavy spring pawl pulls down one tooth of the 50 tooth gear at each revolution of the large wheel, which is fitted with a cam, operating a lever acting on the pawl. Capable of adding up to 5099, the device was marketed to those whose work involved adding long lists of numbers. The adder is over 6" long, with approx. 4 1/4" and 2 1/4" wheels. Good working order.

side view ---- the patent dates ---- advancing mechanism ---- the readout window

THE WEBB ADDER - 19th C. articles and patents

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