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Early mechanical calculators - Carl Walther, c. 1924.

Walther Model RMKZ, S/N 51434
Digits: 10 rotor, 8 counter, 16 accumulator
Dimensions: Body 8"W x 5"D x 5"H, overall width, including handles, 11"W
Weight: 7.9 lbs.
Manufactured:
Gerstetten, Germany, 1948

After the Arithmometer, the pinwheel calculator was the next major mass-market mechanical innovation. It used retractable pins instead of the stepped drum for decimal input. The first practical implementation was that of Poleni in 1709, then Braun in 1720s, and Roth and Staffel around 1840, but was first made successfully for mass production by Willgodt Theophil Odhner a Swedish immigrant to Russia, see video below. Production began in St Petersburg in 1890 and was very successful until the Russian revolution of 1917 when the factory was shut down. From 1892 to the middle of the 20th century, independent companies were set up all over the world to manufacture Odhner's clones and, by the 1960s, with millions sold, It became one of the most successful type of mechanical calculator ever designed.

The machine is built from aluminum-alloy castings and is relatively light in weight. It has a setting check dial and tens-carry on the counter, but no back-transfer mechanism. The carriage is spring-loaded towards the left, and is moved one step at a time by the two vertical levers next to the winding handle. A button at the front releases the carriage detent to allow continuous movement. The accumulator register has small thumbwheels next to each numeral wheel to allow values to be entered directly, eg, in setting up a division.

Carl Walther GmbH is a German company better known for making weapons such as the Walther PPK that James Bond is so fond of. Carl Walther founded his company in 1886, making hunting rifles and selling them in his gunshop in Zella-Mehlis. From 1908 the company started making pistols instead of rifles. Carl died in 1915, and from then on the company was run by one of his sons, Fritz Walther.

The treaty of Versailles at the end of World War I severely restricted arms manufacturing and trade, so Walther had to diversify. In 1924 they started producing calculators. This came about in cooperation with Mercedes, who had a factory in Suhl just a few kilometres away from Zella Mehlis. Mercedes made pinwheel calculators under the Melitta brand, but wanted to focus their production on the Mercedes-Euklid type of machine. Walther then took over the production of the Melitta calculators, and were allowed to sell them under the Walther brand name, too. Soon they started developing them further, including electrically driven models. In 1931 they also manufactured the Tasma, an adding-listing machine with a full keyboard which had until then been made by Thales, though it seems this was never sold under the Walther brand name.

The Walther factory was destroyed in the second world war, no doubt due to its arms manufacturing activities. Zella-Mehlis was in the Soviet-occupied region of Germany, and Fritz Walther decided it was better to rebuild the company and factory in the Allied-occupied region. He and some of his engineers settled in Heidenhelm, where they set up a basic workshop. In about 1947 they were ready to set up a factory to manufacture calculators in the nearby town of Gerstetten and then another in Niederstotzingen. A few years later in 1953 the company had grown enough to restart the arms manufacturing in a new factory Ulm, at which point the calculator business was split off as a separate company, Walther Büromaschinen GmbH.

From 1952 they also started making electrically driven, 10-key adding-listing machines, such as the Walther SR-12. This machine was also sold in the USA by Felt & Tarrant under the name Comptograph 202. Fritz Walther died in December 1966, and was succeeded by his son Karl-Heinz Walther. By the late 1960s the WSR-160 was the only remaining pinwheel model still in production, but its end date is somewhat uncertain (some sources say 1968, others 1971). The other desk calculators became more electronic, and remained in production until the mid 1970s. The Walther Büromaschinen company went public and then became Walther Electronic AG, and later specialized in scanning and sorting machines under the name Walther Data GmbH.

     

Video describes the mechanical principles behind the pinwheel calculating machine. Courtesy of The Visual Guide to Mechanical Computing.                         

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