Heyde & Büttner (Prototype)
This is the prototype of a mechanical calculating machine designed by Gustav Heyde and Karl Otto Büttner of Dresden, which has the German patent No. 26640 and was built on 25. September 1883. Only four of these machines exist today. A very similar prototype with capacity 8 x 9 x 16 is in a private collection in southern Germany. Two others, slightly different from the one in the Arithmeum, are in the Mathematisch-Physikalischer Salon, Dresden (Inv.-No. A II 14), and in the former Brunsviga Collection of the Brunswick State Museum (Inv.-No. Zru 1879-1). According to Schillinger , p. 14, the mechanism works as follows. The numbers are entered in the setting mechanism by means of sliding knobs which move toothed segments below. The position of the slide determines the action of a pawl and the subsequent movement of a cogwheel. These cogwheels are distinctly smaller in this machine than in those of Dresden and Brunswick. By means of further intermediate cogwheels, the entered number is transferred into the result mechanism. A type of con-rod gadget enables an impulse-free operation. Changing from addition to subtraction or from multiplication to division is performed with a lever. This is accompanied by a shift in the position of the result mechanism. While the old mechanical engineer Dr. h.c. Gustav Heyde dated the Dresden machine around 1890, one must assume that it was built around the time it was patented (1883). The date of the Brunswick model is taken to be even earlier: around 1879. In Brunswick one surmises that it is an improved version of the Dietzschold machine of 1876 (see functional model FDM 6120).