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Chebyshev. Later on the french historian Maurice d’Ocagne contacted Chebyshev for description of the machine
       and published an article.
       In fact, both machines of Chebyshev were made only for demonstration purposes. He never seriously thought of
       creating a device for practical or commercial use. His personal innovations are continuous tens carry and auto-
       matic shifting of the carriage from decimal place to decimal place during multiplication. Both inventions became
       popular and were widely implemented in 1930s, when electromotive drives came into use in the quickly growing
       generation of automatic and semi-automatic keyboard calculating machines.

       Odhner arithmometer
                             W. Theophil Odhner invented his mechanical calculator in 1873 in Saint Petersburg. He
                             built 14 machines for Ludvig Nobel, his employer at the time, then patented it in several
                             countries and started serial production in 1890. The arithmometer became one of the
                             most successful type of mechanical calculator ever designed with millions sold in 19th
                             and 20th centuries. In 1924, the Soviet government moved the old production facility to
                             Moscow and commercialized their calculator under the Felix Arithmometer name which
                             went on well into the 1970s. Odhner’s arithmometer was copied, manufactured and sold
                             by many other companies all over the world. It was recognized that, by the end of the
                             1940, the Odhner arithmometer was the most popular portable mechanical calculator in
       W . Theophil Odhner   the world.
           (1845–1905)       Willgodt Theophil Odhner was born in 1845, in Dalby, Värmland, in central Sweden.
                             Odhner studied mechanics and mechanical technology at the Royal Institute of Technol-
       ogy in Stockholm, but although he completed his third year he never finished his study. Finding employment in
       Sweden was difficult in those times and in 1868 Odhner moved to St. Petersburg in Russia where he found a job
       iworking for fellow-countryman Ludvig Nobel – the older brother of the famous Alfred Nobel.
       Odhner must have seen (possibly brought in for some repair) or have read about the Thomas de Colmar arith-
       mometer which was designed in 1822. He thought that he could design a better and more efficient calculating
       machine. His solution was based on a geared pinwheel mechanism and resulted in the well-known barrel-shaped
       calculating machines bearing his name. It was ready for demonstration in 1875. In 1878 he submitted an applica-
       tion for the patent on his invention to the United States Patent Office which was awarded three months later; this
       was soon followed by patents in other countries.
                                                Fortunately Nobel saw the merit of the Odhner machine and asked
                                                him to produce 14 machines. He also gave Odhner some space in his
                                                factory for the manufacture of these machines and he agreed to carry
                                                the costs as well as paying Odhner a salary. The two men agreed they
                                                would later split the profits of this endeavour. Although the first mod-
                                                el carried only 9-digit results, the next version could handle 10-digit
                                                answers and  this  increased
                                                to 11 digits by 1889.  The
                                                machine  had three  regis-
                                                ters: one to manually set the
                                                multiplicand,  one to reg-
         The Odhner arithmometer of 1890       ister the result and one to
       count the revolutions of the crank (i.e. the multiplier). For each manual
       revolution of the crank the multiplicand would be added to the results
       register, while the revolution register kept track of the number of revo-
       lutions. After having done one decimal position the carriage was shift-
       ed one position to the left for the next decimal. Clearing of the registers
       took place through the use of wing-nuts on either side of the carriage
       on earlier models, clearly visible in above illustration. In later models
       the wing-nuts were replaced by crank handles.
       In 1886 Odhner founded the W.T. Odhner, Maschinenfabrik & Metall-
       giesserei in St. Petersburg for the manufacture of his calculators. The
       design  Odhner Paten proved quite reliable and the machine was easy
       to handle.                                                          The patent drawings of Odhner’s 1879

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