Dietzschold’s Demonstration Model

In 1876 in Glashütte, the mechanical engineer Curt Dietzschold (1852 - 1922) began to work on a mechanical calculating machine which would not have the shortcomings of the Thomas machines. He designed a setting and transfer mechanism in which a pawl engages a cogwheel and turns it the right number of steps. Later this was dubbed the “switching pawl principle” and was used very successfully in Hamann’s machines. From 1877 onwards he commissioned the firm Lange & Sons to construct three models which still exist today: No. 3 is in the Mathematical-Physical Salon in Dresden, No. 2 was acquired by the Arithmeum 2006 as part of the Waldbauer collection, and the third, possibly No 1, may have been acquired in 1878 by the Prussian Statistical Office in Berlin. In the same year Dietzschold convinced his colleague Arthur Burkhardt from student days to join him in his endeavors to complete a calculating machine. But in 1879 Dietzschold became the director of the watchmaking school in Karlstein, Lower Austria. Burkhardt then single-handedly changed the setting and transfer system of the machine to the stepped drum system used in the Thomas machines, a decision which Dietzschold deeply resented, as documented in Dietzschold [1882], pp 38-40. No further machines with Dietzschold’s switching pawl mechanism were built. Schematically, the pawl K engages the cogwheel R after the pin D has left the steel segment S; while D moves along S, K is kept from engaging R. The segment S is turned by means of a toothed rod T through an angle of maximally 90° determined by the entered number. Turning the crank moves T forwards and backwards, during which it acts on K via A. When T moves right, K acts on R, and when T moves left, K passes over the cogs of R without moving them. This machine documents in a cardinal way the initial spark that set off the production of mechanical calculating machines in Germany.