Reference / Paper · 2022
Herbert Bruderer's 2022 article on Curt Herzstark and the Curta, its manufacture in Liechtenstein, and what newly found patent documents and design drawings show about the Multiple Curta, a parallel calculator.
The Curta, a Technical Marvel The development of mechanical calculating machines began in the 17th century with Wilhelm Schickard (Germany), Blaise Pascal (France) and Gottfried Wilhelm Leibniz (Germany). It reached its peak after more than 300 years with the Austrian engineer Curt Herzstark, the inventor of the Curta. This technical marvel was manufactured in large numbers in Liechtenstein. In the 1970s, however, digital mechanical calculators and analog logarithmic slide rules were replaced by electronics. The mathematical devices, which were very popular and widely used at the time, are now largely forgotten. Thanks to new discoveries of patent documents and design drawings, there are new insights into the Multiple Curta, the world’s smallest mechanical parallel calculator. BY HERBERT BRUDERER The highly gifted Austrian engineer Curt Herzstark 1,3,4,9 created the Curta, the tiniest mechanical calculating machine in the world. The round-shaped calculator, which reminds one of a pepper mill, was manufactured in high numbers in Liechtenstein from 1948 to 1971. However, the inventor was cheated out of his life's work. Only recently, high-quality design drawings for the Multiple Curta, the world's smallest mechanical parallel calculator, came to light. The University of Birmingham constructed a twelve-fold Curta in 1953. The Curta was the most successful mechanical four-function pocket calculating machine 2, 7, 8, 15, 16, It was even capable of extracting square roots. The Curta is considered the crowning achievement of the 350 year history of mechanical calculating machines. The stepped drum devices remain completely functional to this day. The precision mechanical marvel is the forerunner of today's electronic pocket calculators, which appeared on the market in the 1970s. The early providers included Canon, Hewlett-Packard, Sanyo, Sharp, Olivetti, and Texas Instruments. 18. Curt Herzstark The life of the Austrian inventor Curt Herzstark (1902–1988) (see Figure 1) was overshadowed by tragic events 5, 6, 11, 12, 17: prevention from taking over his parents's calculating machine factory because of the "annexation" of Austria, prisoner in the Buchenwald concentration camp, escape from Soviet persecutors in Thuringia, defrauding with the buildup of mass production for the Curta by the Prince of Liechtenstein, and the resistance of certain Swiss competitors. 1 Figure 1. Curt Herzstark, the inventor of the world's smallest mechanical pocket calculating machine. Although he was Austrian, the Curta was manufactured in Liechtenstein (Credit: Liechtensteinisches Landesmuseum, picture: Sven Beham). Curt Herzstark’s life 5, 6 January 26th 1902 Born in Vienna August 19th 1938 Granting of the main patent (DRP no. 747 073) for the complementation gearwork (complementation stepped drum) th April 13 1939 Granting of the main patent (DRP no. 747 074) for the reduction th October 27 1988 Death in Nendeln, Liechtenstein The Curta is a stepped drum machine 3, 4 Primarily stepped drums and pinwheels were used with mechanical calculating machines. These two devices for mechanical numerical notation were invented by Gottfried Wilhelm Leibniz. The pinwheel was also (probably independently) designed by Giovanni Poleni (Italy). A stepped drum (see Figure 2) is a (broad metal) drum with teeth of different length. The teeth, with staggered length and parallel to the axis of the drum, represent the numerical values 1 to 9. No tooth has the value zero, and all teeth correspond to the number 9. The numeral 1, for example, is represented by one (the longest) tooth and the number 2 by two (the longest and the second longest) teeth. 3 is composed of the longest, the second longest, and the third longest teeth. The stepped drum is also described as a stepped wheel or a Leibniz wheel. 2 Figure 2. Stepped drum. A complete revolution of Gottfried Wilhelm Leibniz’s stepped drum drives a gear wheel of the calculating unit further according to its position, e.g., at zero (top line in the drawing) or at nine teeth (lowest line). (Source: Albert Rohrberg: Theorie und Praxis der Rechenmaschinen). The Curta is a cylindrical calculating machine 3, 4 Most calculating machines are rectangular. However, there were also numerous cylindrical devices (see Table 1). Mass production of stepped drum machines did not begin until around 1850 with the French Thomas Arithmometer. Table 1: Early circular (cylindrical) four-function machines that have been preserved Inventor Braun, Anton Hahn, Philipp Matthäus Hahn, Philipp Matthäus Leupold, Jacob; Braun, Anton; Vayringe, Philippe Müller, Johann Helfrich Roth, Didier Sauter, Johann Jacob Schuster, Johann Christoph Schuster, Johann Christoph Schuster, Johann Christoph Year built 1727 1774 1776 1735 1784 1841 1796 1792 1820 1822 Design Pinwheel machine Stepped drum machine Stepped drum machine Toothed segment machine Stepped drum machine Pinwheel machine Pinwheel machine Stepped drum machine Stepped drum machine Stepped drum machine A pinwheel is a (narrow disc-shaped) gear wheel with nine movable and adjustable pins. The teeth, arranged perpendicular to the shell, can be individually extended or retracted or folded inward and 3 outward. If no pins extend from the wheel rim, this represents the number 0. Nine extended teeth correspond to the value 9. Five extended pins give the value 5. The magnificent circular calculating machines (see Figure 3) are usually one-of-a-kind devices. Figure 3. Müller's stepped drum machine (1784). This cylindrical 14-place four-function machine of Johann Helfrich Müller (Germany) enables calculations in different number systems (base-2 to base-12 number system) by changing the numeral discs (Credit: Hessisches Landesmuseum, Darmstadt). The development of the Curta For a long time there were only heavy, inaccurate or unsuitable calculating aids. Today electronic pocket calculators are commonplace. However, until the 1970s there were practically only: • Portable bead frames, which in fact enabled all four basic arithmetic operations but had no automatic tens carry • Light-weight, easy to use (logarithmic) slide rules, which were incapable of addition and subtraction and inaccurate • Mechanical pocket calculators, such as the sliding bar calculator, which was incapable of multiplication and division and exhibited only semi-automatic tens carry • Heavy mechanical desktop calculating machines, which were capable of all four basic arithmetic operations and had automatic tens carry, but could not be easily transported. Features of the two models The Curta (see Figure 4) is a cylindrical digital calculating machine capable of all four basic arithmetic operations. Contina manufactured two models, a smaller and a larger version: 4 Figure 4. The Curta (Model 2). The Curta pocket calculator is a full-fledged four-function calculating machine (Credit: Liechtensteinisches Landesmuseum, Vaduz, picture: Sven Beham). Curta 1 • 8 places in the setting mechanism, 6 places in the revolution counter, and 11 places in the result mechanism, i.e. 8 x 6 x 11 • 53 mm diameter, 85 mm high, 230 g weight without sleeve, 330 g with sleeve • The manufacture and assembly of a Curta 1 took 9–10 hours. Curta 2 • 11 places in the setting mechanism, 8 places in the revolution counter, and 15 places in the result mechanism, i.e. 11 x 8 x 15 • 65 mm diameter, 90 mm high, 360 g weight. Design drawings The large-format design drawings for the Curta are extremely complex. Since they would no longer be readable following reduction in size it is unfortunately not possible to reproduce them here. The following illustration (see Figure 5) serves only to convey an initial impression. 3, 4, 12 5 Figure 5. Design drawing for the Curta 1. This drawing depicts the base body of the high-precision calculating machine (Source: Museum Mura, Schaanwald FL). New documents for the Curta from Austria, Germany and Switzerland In the course of researching the history of computing, on November 25th 2014 drawings of the Curta calculating machine, originally called the "Liliput", were discovered at the Schreibmaschinenmuseum Beck in Pfäffikon ZH (Switzerland). They were prepared in the Buchenwald concentration camp by the inventor, Curt Herzstark. The legacy, which Herzstark's partner in life Christine Holub donated to the museum's owner Stefan Beck, included letter correspondence with long since vanished well known Swiss calculating machine manufacturers as well as lists of customers. Furthermore, of particular interest is a marketing conctract with the Rheinmetall-Borsig company in Sömmerda (Thuringia), concluded shortly before Herzstark's dramatic escape from Thuringia, for which a previously unknown transcript came to light. New is also an informative authentic account of Herzstark's colleague Elmar Maier on the further development of the Curta (Curta 1a, 2a and electrification). Further documents exist in the Swiss Federal Archives in Bern. The Multiple Curta as the world's smallest mechanical parallel calculator In 2015 previously unknown design drawings and patent documents relating to a multiple calculator of Curt Herzstark came to light in Switzerland. In 2017 a paper concerning a mechanical parallel calculator with 12 Curtas dating from 1953 in England was rediscovered. 6 Mass production of the Curta in Liechtenstein The first devices were manufactured in 1948. The two diagrams below (see Figures 6–7) illustrate the development of mass production. Figure 6. Manufacture of the Curta 1 from 1948 to 1970. A pronounced drop production occurred in 1953 (Credit: Bruderer Informatik, CH-9401 Rorschach, Switzerland). Figure 7. Manufacture of the Curta 2 from 1953 to 1971. The number built dropped dramatically in 1957 and especially in 1971 (Credit: Bruderer Informatik, CH-9401 Rorschach, Switzerland). A mechanical parallel calculator from Liechtenstein On November 14th 2015 the investigation of Curt Herzstark's estate brought to light exceptionally interesting original drawings and patent documents at the Schreibmaschinenmuseum Beck in Pfäff- 7 ikon ZH (see Figures 8–9) for a previously unknown multiple calculating machine, the world's smallest mechanical parallel calculator. According to the newly discovered patent documents, any number of circular machines can be coupled. In particular, Herzstark describes the following configurations: • Two Curtas standing next to each other • Three Curtas stacked over each other • Four Curtas standing next to each other • Five Curtas in a circular arrangement. Features of the multiple calculating machine The parallel calculator is distinguished by the following features: • All machines are driven simultaneously by a single hand crank. • All devices can be (by axially shifting the drive shafts) changed jointly or individually to another basic arithmetic operation. This is possible even when the individual calculating machines are set to different arithmetic operations. • All counting mechanisms can be simultaneously or individually advanced with the correct number of places (decade-wise) in both directions of rotation. • All result mechanisms and/or all revolution counters can be reset to zero jointly or individually. Curt Herzstark adds: "In addition, the multiple calculating machine can also be operated with an electric drive" (see patent specification no. 195 147, page 5). Double, quadruple and quintuple Curtas The entirely surprising findings show that the Viennese inventor designed not only individual devices, but also Multiple Curtas. Calculating machines with several counting mechanisms were known from earlier times, for example the double or triple Brunsviga, Marchant, Millionaire, Monroe, Thales, and Triumphator machines. They accelerate the calculation process and were used for surveying and liquidation calculations. The following illustrations are concerned with the Curta 1. In order to simplify operation, Herzstark designed a further form of the Double Curta with a base plate (additional patent). 8 Figure 8. The Double Curta. The original drawing shows two mechanical pocket calculating machines arranged next to each other. The drive crank activates the main drive shafts via bevel gears and spur gears. A chain drive is also possible (Source: Schreibmaschinenmuseum Beck, Pfäffikon ZH). The following variant with four cylindrical machines is missing from the patent application: 9 Figure 9. The Quadruple Curta. This original drawing shows four Curtas removably attached to a socket, which is equipped with coupling, drive and control elements. The joint drive crank is connected to the stepped drum shafts by a chain drive (Source: Schreibmaschinenmuseum Beck, Pfäffikon ZH). Acceleration of the arithmetic operation The high-precision Curta is capable of all four basic arithmetic operations. The coupling of several devices accelerates arithmetic operations considerably. For example, with a Quadruple Curta one enters the values (multiplicands) 137, 263, 389 and 491 and multiplies these by the number 7 (multiplier). The four multiplications are then performed simultaneously (in this case with seven rotations of the crank). One can simultaneously divide the numbers 623, 511, 301 and 259 (dividends) by 7 (divisor). Possible applications were, for example, the simultaneous conversion of a price list to several currencies, the simultaneous calculation of piece prices for goods, or the simultaneous determination of the x and y coordinates in surveying. Patent specifications for the multiple calculating machine The following Austrian patents are known for the multiple calculating machine of Curt Herzstark: Patent specification no. 195 147 of January 25th 1958 (basic patent): Submitted: October 19th 1954 Granted: May 15th 1957. Patent specification no. 205 775 of October 10th 1959 (additional patent): Submitted: December 15th 1954 Granted: March 15th 1959. The first application for a multiple calculating machine patent in Austria was already submitted on December 20th 1949. Efforts were also made to patent the device in America. Earlier Austrian patents for the customary Curta bear the numbers 747 073/192, 747 074/191, and 166 581, 163 380. 10 The British Twelve-fold Curta for matrix calculations In the 1940s and 1950s the periodical Mathematical Tables and other Aids to Computation, founded in 1943, was the leading international journal for computer technology. Since 1960 it has the title Mathematics of Computation. In the issue of July 1954 (see Figure 10) A. Opler13 called attention to the Twelve-fold Curta in the section "Other aids to computation": Figure 10. The mechanical parallel calculator. Review of the article of James Robb in the journal Mathematical Tables and other Aids to Computation (1954) (Credit: MTAC). James Christie Robb (1924–1999)10, of the Chemistry Department of the University of Birmingham, had submitted an article14 about a Twelve-fold Curta to the Transactions of the Faraday Society (see Figure 11) that was received on July 20th 1953. The journal was published from 1905 to 1971. Robb was active at the University of Birmingham from 1948. In 1956 he was appointed Professor for Physical Chemistry and in 1983 became the Head of the Department of Chemistry. The parallel calculator designed by Robb was built by S. Traver, with the support J. Harcourt. The twelve Curtas (Model 1) are mounted in a circle on a Dural aluminum alloy octagonal base provided with two handles. Each cylindrical calculator has 8 places in the setting mechanism, 6 in the revolution counter, and 11 in the result mechanism. The base plate has three levers, (from left to right) one for shifting the carriage (6 different decimal places), one for resetting to zero, and one for multiplication. The lever at the left raises the carriage and rotates it to one of the six positions (ones, tens, hundreds, thousands, etc.). According to the description, there is in principle no limit to the number of Curtas that can be combined. In this contribution the Curta and the Contina are mentioned, but not Curt Herzstark. The Liechtenstein Contina AG donated the twelve Curtas. The device simplified the solution of linear simultaneous equations. It served for the calculation of inverse matrices. One could multiply twelve arbitrary (1- to 8-place) values by the same (positive or negative) factor simultaneously. The article refers to a patent application no. 10993/53 with the British patent office. However, whether a patent was granted is not known. There is no corresponding entry in the European patent database. Herzstark already submitted the first patent application for the multiple calculating machine to the Austrian patent office in Vienna on December 20th 1949, and in 1953 he had already left the manufacturer Contina. 11 Figure 11. The Twelve-fold Curta. The world's smallest mechanical parallel calculator was built at the University of Birmingham in 1953 and comprises twelve Curtas (Model 1) (Credit: Royal Society of Chemistry, London). Acknowledgments The author is very grateful to Stefan Beck, Elmar Maier, John McMinn, Hansjörg Nipp, and the unknown reviewers for their support. References This paper is based on the author’s book on the history of computing and oral history interviews with Elmar Maier (Curta development engineer) and Franz Oehry (head of assembly and service), as well as with Curt Herzstark Junior, Christine Holub, Arnold Kessler, Helmut Waldbauer, and others. 1. Anthes, E. Die Wiener Ingenieurfamilie Herzstark und die Erfindung der Rechenmaschine Curta. Blätter für Technikgeschichte 46/47 (1984/85), 115–137 2. Beyer, H. Die rechnerischen Vorteile der „Curta“-Rechenmaschine. Österreichisches IngenieurArchiv 9, 1 (1955), 31–37 3. Bruderer, H. Meilensteine der Rechentechnik, De Gruyter Oldenbourg, Berlin/Boston, 3rd edition (2020), 2 volumes 4. Bruderer, H. Milestones in Analog and Digital Computing, Springer Nature Switzerland AG, Cham, 3rd edition (2020), 2 volumes, translated from the German by John McMinn 5. Herzstark, C. Kein Geschenk für den Führer. Schicksal eines begnadeten Erfinders, Books on demand GmbH, Norderstedt, Germany (2005) 6. Herzstark, C. The inventor of the Curta calculator, Oughtred Society, Roseville, CA (2017) 7. Holecek, K. Eine neuartige Rechenmaschine – eine interessante feinmechanische Konstruktion. Maschinenbau und Wärmewirtschaft 9, 6 (1954), 155–162 8. Holecek, K. Neue konstruktive Wege im Rechenmaschinenbau. Feinwerktechnik 55, 6 (1951), 129–136 9. Kradolfer, P. Die Curta und ihr Erfinder Curt Herzstark. Historische Bürowelt 35 (1993), 19–31 10. Lehrle, R. S. James C. Robb 1924–1999. Chemistry in Britain 37, 1 (2001), 57 11. Maier, E. Ein prägender Lebensabschnitt. Rechenmaschine Curta (Patent Herzstark),2014, http://dx.doi.org/10.3929/ethz-a-010345785 12 12. Nipp, H. Curta, Carena & Co. Geschichte der Contina in Mauren, Alpenland-Verlag AG, Schaan Liechtenstein (2017) 13. Opler, A. 1143. James C. Robb, "A calculator for aiding matrix calculations", Faraday Soc. Trans. 50 (1954), 8–12. Mathematical tables and other aids to computation 8, 47 (1954), 181 14. Robb, J. C. A calculator for aiding matrix calculations. In: Transactions of the Faraday Society 50 (1954), 8–12 15. Sigrist, W. Die Curta-Rechenmaschine– eine Legende. Vermessung, Photogrammetrie, Kulturtechnik 90, 3 (1992), 138–142 16. Stoll, C. Rechnen mit der Kurbel. Spektrum der Wissenschaft 4 (2004), 87–94 17. Tomash, E. An interview with Curt Herzstark, Nendeln, Liechtenstein, September 10th-11th 1987, Charles Babbage Institute, University of Minnesota, Minneapolis. 18. Trost, E. Aufbau und Wirkungsweise einer Taschenrechenmaschine. Technische Rundschau 49, 50 (1957), 21–23. Meilensteine der Rechentechnik/Milestones in Analog and Digital Computing, volume 1 (Credit: De Gruyter Oldenbourg/Springer Nature 2020) Bruderer, Herbert [2020a]: Meilensteine der Rechentechnik, De Gruyter Oldenbourg, Berlin/Boston, 3. Auflage 2020, Band 1, 970 Seiten, 577 Abbildungen, 114 Tabellen, https://www.degruyter.com/view/title/567028?rskey=xoRERF&result=7 Bruderer, Herbert [2020b]: Meilensteine der Rechentechnik, De Gruyter Oldenbourg, Berlin/Boston, 3. Auflage 2020, Band 2, 1055 Seiten, 138 Abbildungen, 37 Tabellen, https://www.degruyter.com/view/title/567221?rskey=A8Y4Gb&result=4 Bruderer, Herbert [2020c]: Milestones in Analog and Digital Computing, Springer Nature Switzerland AG, Cham, 3rd edition 2020, 2 volumes, 2113 pages, 715 illustrations, 151 tables, translated from the German by John McMinn, https://www.springer.com/de/book/9783030409739 Herbert Bruderer Seehaldenstrasse 26, Postfach 47, CH-9401 Rorschach, Switzerland +41 71 855 77 11, [email protected], [email protected] March 5, 2022 13