Odhner




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	Original Odhner



	Original Odhner Pinwheel calculator with 10-digit setting register, 13-digit accumulator register, 8-digit revolutions register. Made in Sweden in the period 1935-1945. 345 x 140 x 115 mm (13.6" x 5.5" x 4.5"), 5 Kg (11 lbs.).


		With front covers removed, showing the pinwheels, at the top, the accumulator register below, and the revolutions register on the left.


	Close up of the pin wheels, looking from the right, with the number of pins raised on each wheel depending on the number set by each lever (from top to bottom 0087654321). These act as gear teeth when the crank handle is turned.



		A later model of Odhner pin-wheel calculator, probably from the 1960s, has the same layout as the older model at the top of this page but with a more modern design.

	This type of calculator, the pin-wheel calculator, was invented by Willgodt T. Odhner in St. Peterburg, Russia, in 1874. (A calculator on similar principles had been invented independently 2 years earlier by Frank Baldwin in the USA, but the Odhner was the successful design). Following the Russian Revolution of 1917 and the nationalisation of the factory there, production moved to Sweden and the name "Original Odhner" was adopted. This was the most successful type of general purpose mechanical calculator (ie. intrinsically capable of multiplication and division and not just "adding machines"). Up to the early 1970s dozens of manufacturers made machines based on and with a general resemblance to the Odhner, see below. Kevin Odhner (yes, related to the inventor) has a fascinating history of *Odhner* mechanical calculators at http://mywebpages.comcast.net/wtodhner/ Basic method of operation - When one of the setting levers is moved to a number then that number of pins is raised on the corresponding pin-wheel (ie. moving a lever to '7' raises 7 pins). Turning the crank handle rotates all the pin-wheels, and their attached setting levers. The raised pins act as gear teeth and advance the individual accumulator wheels (with numbers at bottom right) by the number of pins, so adding the set number to the accumulator. Multiplication is fairly straight forward since the handle can be turned several time quickly to add the same number to the accumulator. The numbered wheels at bottom left keep a record of the turning of the handles. Moving to the next decade involves pressing the appropriate lever at the front. The small cranks on each side at the front are for clearing the device. For further information on performing the basic arithmetic operations see Operating a Pinwheel Calculator in the "Collecting Calculators" section of this site. To see John Wolff strip down an Odhner calculator to reveal its nearly 700 parts, and put it back together, go to http://home.vicnet.net.au/~wolff/calculators/pinwheel/Odhner127/Odhner127-1.htm The Odhner machine here has the classic arrangement of the pin-wheel calculator. Variations are shown on the modern Facit models (which use keys for setting, for increased speed). Some further pin-wheel calculators which appear on the site are shown below: *Click on an image here for more pictures and technical details of these calculators:*