The Development of the diesel engine
By Lynwood Bryant
Mr. Bryant, professor emeritus of the Massachusetts Institute of Technology, is a visiting research scholar at the Eleutherian Mills Historical Library. He wishes to acknowledge his indebtedness to the late Friedrich Sass, the late Eugen Diesel, the late Georg Strossner, and Kurt Schnauffer for their writing and especially for many helpful conversations about Diesel and his engine; to Irmgard Denkinger, another expert on Diesel, for her kindness and her guidance in the MAN Werkarchiv in Augsburg; and to A. R. Rogowski, Professor Emeritus of Mechanical Engineering at MIT, for ten years of patient explanation of the mysteries of engines.
In 1912, when the diesel engine was about twenty years old, just coming of age after a prolonged infancy and a painful adolescence, it was the subject of a celebrated controversy, in which the inventor, Rudolf Diesel (1858-1913), and two distinguished professors of engineering discussed the very topic that concerns us in this symposium: the distinctions among invention, development, and innovation as parts of the total process of technological evolution. These three words are commonly used rather loosely, and I do not need to make very sharp distinctions among them because my main point is that in the real world the three processes to which these words refer are not sharply separated. But let me begin by saying that I am thinking of an invention as the appearance of an idea in someone’s mind, an eventing intellectual history; of development as the conversion of an idea into some kind of workable reality, such as an engine that runs; and of innovation as the introduction of the developed invention into the economy as a useful, salable product.
The 1912 controversy began when Diesel heard that Adolph Nagel of Dresden was planning a book on the history of the diesel engine. Diesel was naturally nervous about what Nagel would say, for he was a sensitive and proud man, and there had been some troublesome uncertainties and misunderstandings about the invention of his engine and the validity of his patent. So the inventor prepared his own account of the origin of his engine and presented it at a meeting of the German Society of Naval Architects in November 1912. In the discussion period following the paper, two professors launched an attack on Diesel that raised disturbing questions about his professional integrity. Their main point was that the engine that emerged from the development process was not the same as the engine that Diesel invented, and that credit for it should go to the practical engineers who developed it. Diesel, they said, was a promoter, a mere businessman, not an inventor.1 This was the unkindest cut of all, for Diesel was an engineer with scientific pretensions. He thought of himself as the James Watt of the 20th century.
Four books grew out of this controversy, one by Diesel and three by his critics. They were all published shortly before or shortly after Diesel’s mysterious death,2 and they all include theoretical discussion of the nature of invention and development, and argument about Diesel’s work. So the Diesel story is well documented in the sense that much has been written about it, but the literature is mostly polemical or promotional, so that there are still many uncertainties about what actually happened.
I propose to go over this story once more, and use it as a case study in the process of development. I shall try to indicate what different kinds of activity were going on at different times in the course of the early evolution of this engine, and then make some general remarks about the nature of development and how it is related to invention on the one hand and innovation on the other.
My main point is that these processes may be conceptually distinct, but when you look closely at what is going on, it is hard to say when one leaves off and another begins. It may be better to regard them not as chronological stages but as different kinds of forces operating in an evolutionary process, or different types of human interest and activity, all more or less involved in all stages of technological progress.
First Period: Invention, 1890 - 1893
The first period begins with the conception in Diesel’s mind, which occurred in 1890 or 1891, and ends with the first attempt at a real engine in 1893. In this period the engine is a concept, not a reality, and its history is intellectual history, the story of how a man got an idea and was guided by this idea.4
The system of ideas that constitutes the diesel engine includes a dozen important concepts and techniques, all of which appeared before 1890. But one key idea Diesel claimed as novel: the idea that combustion in an internal-combustion engine could be made to take place at constant temperature, that is, isothermally. As Diesel conceived it, such an engine (on a down stroke of the piston) would draw in a charge of plain air, and then (on an up stroke) compress it to a very high pressure and temperature. Then just as the piston started down again, fuel would be introduced gradually into the hot, expanding air in such a way that the tendency of the temperature to rise with combustion would be exactly counterbalanced by the tendency of the temperature to fall as the air expanded.
If this way of achieving isothermal combustion works, thought Diesel, then an approximation to the ideal engine embodying the Carnot cycle is possible. Such an engine would be much more efficient than any existing heat engine because it would operate through a wider range of temperature, and, with isothermal combustion, all the heat added would be converted to work on the piston. In a Carnot heat engine the heat to be converted into work has to be added at the highest temperature of the cycle and it has to be added without raising the temperature further. The practical difficulty in realizing this ideal in a combustion engine is that it is hard to see how combustion can take place without a rise in temperature. This was the essence of Diesel's invention: he conceived a way of burning fuel in an engine without raising the temperature.5
Diesel began by formulating the idea carefully and working out the details of a possible engine. He prepared a manuscript, with supporting calculations and illustrations, and sent it out for criticism to several experienced engineers and industrialists. One or two critics said encouraging things, but mostly they regarded the engine as impractical because of the extreme pressures and temperatures required. Diesel went back to the drawing board to prepare a more modest proposal for a more realistic engine, and with this revision as a supplement, sent the manuscript to Springer to be published.
Diesel had also formulated his ideas in the form of a patent application, which went through a similar process of negotiation and revision. The patent was issued and the book published early in 1893.6
Meanwhile Diesel had offered his engine, or his idea for an engine, to a number of machine-building firms (it was clearly much too large a project to be developed by a single man in a home workshop) and was rejected by all of them, but as a result of a second approach with more modest claims, the Maschinenfabrik Augsburg agreed to help Diesel develop his engine. This was a large firm led for almost fifty years by Heinrich Buz, an industrial statesman who plays a role in the Diesel story something like the role of Boulton in the Watt story.7 After the patent was issued, the firm of Krupp agreed to join the Maschinenfabrik Augsburg in this project, to share the expenses of development, and to pay Diesel a salary of 30,000 marks a year while he worked on the development.8 It was a good bargain for Diesel.
When Buz called for drawings, Diesel already had them prepared, for a two-cylinder, 50-horsepower engine. Buz proposed a more modest start, with a one-cylinder, 25-horsepower unit. There was no model, no preliminary work with components or processes. Diesel was so sure of himself that he moved at once to a full-size working engine. To him it was a scientific engine, built on sure thermodynamic principles.
I am labeling this first period “invention” because what is going on is primarily mental activity: thinking, calculation, argument, writing. But it is by no means a simple conception of an idea and nothing else. It includes an elaborate consideration of what is involved in realizing the idea, and a good deal of hard work in trying to sell the idea, to secure the endorsements of- scientists and the financial support of business men. I notice that the compromise between idea and reality, which we usually associate with development, is there trom the beginning and that the business negotiations and the balancing of economic interests, which we expect to be dominant in the later stages, have an important bearing on the early decisions to undertake development.
Second Period: Making the First Real Engine, 1893-97
The second period was a four-year struggle to get an engine that
would run, a struggle that took place inside a large steam-engine
factory in Augsburg. Diesel was in direct charge of the work himself,
usually with one or two full-time mechanics assigned to the project.
Now what was Diesel doing during this period? We have a great
deal of information about the technical work that was going on, for
Diesel kept a meticulous journal in his own hand and wrote a book
about it. He even kept thousands of indicator diagrams, so that you
can still tell how the engine was doing on any given day, if you want
to.
Reference
- Diesel's paper appeared under the title “Die Entstehung des Dieselmotors” in Jahrbuch der Schiffbautechnischen Gesellschaft 14 (1913): 267-355, with a transcript of the following discussion on pp. 355-67. Marine engineers were especially interested in diesel power at this time. The major powers had recently adopted it for submarines, and the first motor ship had crossed the Atlantic in 1911.
- The four books were: Rudolf Diesel, Die Entstehung des Dieselmotors (Berlin, 1913), which is the 1912 paper, slightly revised, without the following discussion; P. Meyer, Beutrage zur Geschichte des Dieselmotors (Berlin, 1913); J. Luders, Der Dieselmythus: Quellenmdssige Geschichte der Entstehung des heutigen Oelmotors (Berlin, 1913); and A. Riedler, Dieselmotoren: Beitrige zur Kenntnis der Hochdruckmotoren (Berlin, 1914). The inventor's son, Eugen Diesel, wrote two books and many articles about his father, which tend to be a little colorful and obscure, but they are fundamentally sound, I think, and the best source for biographical information. They also include technical information about the development of the engine. The standard biography is Diesel: der Mensch, das Werk, das Schicksal (Stuttgart, 1937). This book was reissued a number of times, at least once with sensitive passages slightly revised. Another important biographical work of Eugen Diesel’s is Jahrhundertwende: Gesehen im Schicksal meines Vaters (Stuttgart, 1949).
- Diesel disappeared from a channel steamer in the night of September 29-30, 1913. His body was recovered ten days later by a pilot boat at the mouth of the Scheldt River and returned to the sea, but unmistakably identified by articles taken from the body. Lurid rumors appeared at once and persist to this day, for example the legend that Diesel was executed by the German secret service because he was about to betray submarine secrets to the British. All known facts are consistent with the conclusion that he was a suicide. He was in financial trouble, and deeply disturbed by these attacks on his integrity.
- The best summary of this piece of intellectual history is in Friedrich Sass, Geschichte des deutschen Verbrennungsmotorenbaues von 1860 bis 1918 (Berlin, 1962). The last third of this monumental work is an excellent history of the diesel engine. It rests on several years of research by Kurt Schnauffer, which is recorded in many volumes of typescript now in the library of the Deutsches Museum in Munich. Schnauffer’s own account of the invention is “Die Erfindung Rudolf Diesels,” Zeitschrift des Vereines deutscher Ingenieure 100 (1958): 308-20 (hereafter cited as ZV DI). All the books cited in note 2 discuss the invention. Paul Meyer, the most objective and temperate of these contemporary critics of Diesel’s work, wrote his book in 1913 on the basis of some experience with Diesel—he worked with him for a while beginning in 1898—but without access to Diesel's papers. Thirty years later, during the Second World War, he went through the Diesel papers and wrote a new history of the invention of the diesel. This work was sponsored by the Verein deutscher Ingenieure (VDI) but never published. It remains a manuscript entitled “Die Geschichte des Dieselmotors” in the Diesel papers in the Deutsches Museum. Meyer later published two important articles based on this work:“Aus der Enstehungsgeschichte des Dieselmotors,” Schweizerische Bauzeitung 66 (1948): 485-87; and “War der Dieselmotor jemals durch Patente geschiitzt?” Schweizerische Bauzeitung 67 (1949): 309-10.
- My article “Rudolf Diesel and His Rational Engine,” Scientific American 221 (August 1969): 108-18, tries to explain the Carnot cycle and its relation to the diesel engine. The famous Carnot cycle was first described in Sadi Carnot, Réflexions sur la puissance motrice du feu (Paris, 1824).
- The German patent is number 67,207, dated February 28, 1892. (Another patent, number 82,168, dated November 30, 1893, is for a modified process and was applied for after the experimental work began.) The book is Theorie und Konstruktion eines rationellen Wirmemotors zum Ersatz der Dampfmaschinen und der heute bekannten Verbrennungsmotoren (Berlin, 1893). An English translation by Bryan Donkin (London, 1894) omits some material on applications of the engine that appears in the German original. The idea of achieving this kind of isothermal combustion in an engine appears in Otto Kohler, Theorie der Gasmotoren (Leipzig, 1887), and the engine that Kohler hypothesizes is similar in a number of interesting ways to the engine that Diesel describes in his book and his patent. This prior publication of Diesels key idea was a disturbing threat to the validity of the patent. Diesel said that Kéhler’s book was unknown to him at the time. But Kohler’s idea was picked up and published in F. Grashof, Theorie der Kraftmaschinen (Hamburg and Leipzig, 1890). This is the third volume of Grashof’s Theoretische Maschinenlehre. It is hard to see how Diesel could have overlooked this book by a distinguished authority in his field.