Visit the Kinematic Models for Design - Digital Library (KMODDL).
KMODDL is a collection of mechanical models and related resources for teaching the principles of kinematics--the geometry of pure motion. The core of KMODDL is the Reuleaux Collection of Mechanisms and Machines, an important collection of 19th-century machine elements held by Cornell's Sibley School of Mechanical and Aerospace Engineering.
Writing to Cornell's president Andrew D. White in 1882, Dr. Franz Reuleaux enthusiastically describes his kinematic mechanisms that White has purchased for the teaching of mechanical engineering. Reuleaux's basic field was machine design, but within that, his speciality - avocation, really - was kinematics: the mathematical description of motion.
Born in Germany in 1829, Reuleaux was the fourth son of steam engine designer Johann Josef Reuleaux, who was himself the son of a master engineer. At the time of his correspondence with White, Reuleaux was rector of the Technische Hochschule at Charlottenburg near Berlin and had quite literally written the book on machine kinematics: Theoretische Kinematik: Grundzüge einer Theorie des Machinenwesens. Professor Alexander B.W. Kennedy of Great Britain translated it into English in 1876, the year after publication, under the title Reuleaux's Kinematics of Machinery: Outlines of a Theory of Machines.
In the proliferation of machines at the height of the Industrial Revolution, Reuleaux was trying to make sense of it all, systematically analyzing and classifying new mechanisms based on the way they constrained motion. He hoped to achieve in engineering the logical order than Linneaus had brought to biology the century before with his classification of organisms. The result would be a library of mechanisms that could be combined to create new machines, much as computer-programming routines are combined today to create new software applications.
Kinematics flourished in the 19th century as machine inventors learned to transmit information and forces (power) from one element in the machine to another. Scientific American featured a new invention in every issue. Steam-and water-based machines revolutionized the l9th century, but both of those energy sources generate circular motions, creating the need to convert these steady circular motions into nonsteady linear and curvilinear motion for machine applications. The challenge to create input-output kinematic devices that could convert circular motion into noncircular, complex, three-dimensional, intermittent motions attracted both practical inventors as well as mathematicians. Thousands of mechanisms were invented, designed, and built, nurturing the widespread use and manufacture of machinesaa process analogous to the plethora of electronic circuits in the early 20th century and software in the late 20th century.
Franz Reuleaux's mission was to codify, analyze, and synthesize kinematic mechanisms so that engineers could approach machine design in a ration-al way. He laid the foundation for a systematic study of machines by defining clearly the machine and mechanism, determining the basic building blocks, and developing a system for classifying known mechanism types. Reuleaux created at Berlin a collection of over 800 models of mechanisms and authorized a German company, Gustav Voigt, Mechanische Werkstatt, in Berlin, to manufacture these models so that technical schools could use them for teaching engineers about machines.
Reuleaux was also one of the first to use an abstract symbol representation of machines, inventing the idea of a kinematic pair. Each pair had a different symbol, and each mechanism would be described by a collection of symbols or word. A complete assembly of mechanisms is then a sentence of words in this symbol language.
By 1907 some 368 models were available in the Voigt catalog, and the Cornell collection was reported to number 266 items. Minutes of the Cornell University Board of Trustees meeting on June 14, 1882, reveal the funding for the acquisition: "Acknowledges a pledge of $8,000 from the Honorable Hiram Sibley of Rochester to secure the duplicate of the Reuleaux models in the possession of the Imperial Government of Germany." But there's no clear record to explain how or why White came to purchase the collection. At the time of Reuleaux's book on theoretical kinematics in 1875, the German engineer began to travel abroad and became a member of juries of world exhibitions. One story of the acquisition suggests that White saw Reuleaux's display at the International Exhibition of 1876 at Philadelphia and offered to buy the collection for Cornell to save the German government the cost of shipping it back.
The two may indeed have met in Philadelphia. There is evidence in the reports of the U.S. Centennial that White and Reuleaux both attended the International Exhibition of 1876 at Philadelphia. Reuleaux, listed as a commissioner-general for the German Empire, assisted in the judging of the education and science group. The official list of judges also includes Andrew D. White of Ithaca, New York. But Reuleaux's letter of 1882 reveals, however, that he himself supervised the shipping of the collection, not from Philadelphia but from Voigt's workshop in Germany.
However it came about, the acquisition of Reuleaux's famous collection of kinematic models took place amid a watershed for Cornell's mechanical engineering program as well as American engineering education. In the first decade of its existence, the university had developed a curricula in the mechanic arts as required of a land grant recipient, based on a "shop culture" model. Young men with a farm or mechanical skills background were recruited to learn how to construct mechanical machines and machine components. The major proponent of this system was Professor John Sweet. At the same time, Professor Robert Henry Thurston of the Stevens Institute in Hoboken, N.J., was developing a different curriculum, a "classroom culture" model based on laboratory testing and scientific and mathematical principles.
Sweet's departure from Cornell in 1879 brought a turning point in teaching philosophy. A trustee committee was formed to examine the instruction and organization of the Sibley College, and as a result, in 1885, Thurston was named director of the newly organized Sibley College of Mechanic Arts and Mechanical Engineering. He quickly set about building the mechanical engineering program on a new educational model based on a balance of scientific and mathematical fundamentals, engineering science, and practical shop experience. The Reuleaux models were a cornerstone of this effort; in a letter to White in 1886 asking for financial resources to rebuild the program, Thurston comments that the collection was one of the few strong assets of the college.
There is little reference in archived materials to the use of the Reuleaux collection in the mechanical engineering curriculum, but there is a set of 40 index cards, with descriptions of various mechanisms in the Cornell collection. These cards reference Reuleaux's Kinematics of Machinery as well as other books on kinematics in the late l9th and early 20th century and appear to have been written in the 1940s or 1950s. One possibility is that they were used in the original Sibley Hall Museum display before the collection was moved to Upson Hall around 1950.
A sampling of the collection as described in these cards includes the following devices (top to bottom at right).
- The pump mechanism known as Ramelli's Rotary Pump was first described in 1588 by the Italian military engineer, Agostino Ramelli (1531<>-1610). This mechanism found application in mid-20th century household refrigerator -compressors.
- The Pappenheim Chamber Wheel gear is the forerunner of modern gear pumps. Versions of this mechanism have been in existence for over 300 years.
- The Isosceles Slider Crank Train was used in an early steam engine in 1816. This mechanism can be used to form ellipses. Its invention has been attributed to Leonardo da Vinci (1452<>1519) for machining elliptical surfaces.
- The Crown-Wheel Escapement is associated with the Dutch scientist Christian Huygens, who designed the first pendulum clock in 1657. This mechanism allowed the weight of a hanging mass to regularly impart energy to the oscillating pendulum. The Cornell collection contains eight of these clock escapement mechanisms; they are the most elaborate devices in the set and can run for a short time by suspended weights.
- The Pin-Wheel Escapement was invented by Amant in 1741. It was employed in tower clocks and French-made pendulum clocks.
The study of kinematics as a separate discipline in mechanical engineering dwindled by the early l950s, partly because it became recognized that dynamics as well as kinematics was important in the design of machines. Reuleaux and other kinematicians had all but ignored dynamics. In the late 20th century, however, kinematics has seen a renaissance due largely to the development of high-speed computers for computer-aided design and engineering. Mechanisms still form a vital component of design in the automotive, aircraft, space, and manufacturing industries, as well as in the electronics industry.
Because of widespread destruction in Germany in World War II, the Cornell collection, inventoried recently at 218 pieces, appears to be the largest remaining collection of Reuleaux models. The University of Hannover in Germany has about ten models from Reuleaux's own laboratory, not Voigt's workshop and the Stevens Institute in Hoboken, N.J., is said to have a few models. But the Smithsonian Institution has none.
Cornell's Reuleaux collection offers a glimpse of the 19th century's fascination with machines. Moreover, these models still provide elegant demonstrations of engineering concepts and mathematical formulas. And engineers are still asking the same questions that Reuleaux once asked: "Are there principles of design? How does the mind invent things? Can invention be explained by logic? Can machines be programmed to invent other machines?"
Perhaps the answer that Reuleaux proposed is still the best to be found: "He who best understands the machine, who is best acquainted with its essential nature, will be able to accomplish the most by its means."
Professor Francis C. Moon Ph.D. '67 joined the faculty at Cornell in 1975. His research interests include nonlinear dynamics and chaos, dynamics of material processing. He is a member of the National Academy of Engineering. For more information about the Cornell Reuleaux Collection and about the efforts to support refurbishment and display of the models, contact Dr. Moon at the Sibley School of Mechanical and Aerospace Engineering, Cornell University, 204 Upson Hall, Ithaca, NY 14853-7501.