The Silent Otto

The Silent Otto

LYNWOOD BRYANT

The story of the gas engine that I am calling the Silent Otto—the first |

| engine to operate on the four-stroke cycle, and the first to achieve com- |

| pression of the charge within the working cylinder—has been told be- |

| fore.! But I should like to go over it again in order to consider a ques- |

| tion that still seems significant to a historian interested in technology |

| and culture: Why was this engine suddenly successful after seventy- |

| five years of rather fumbling efforts to develop an internal-combustion |

| engine? |

| Nicolaus August Otto (1832-91) built the first Silent Otto in 1876 |

| in the Gasmotorenfabrik Deutz near Cologne (Fig. 1). In its original |

| form the engine had one horizontal cylinder, drew in a charge of illu- |

| minating gas and air through a slide valve, compressed it within the |

| cylinder with a compression ratio of about 24:1, and ignited it with |

| a flame. The engine developed about three horsepower at a speed of |

| 180 revolutions per minute, had a thermal efficiency of about 14 per |

| cent (two or three times as good as a comparable steam engine), and |

| weighed about a ton per horsepower.2 They called it “silent” not be- |

| cause you could not hear it when it was running—you certainly could |

| —but because it ran much more smoothly and quietly than its immediate |

| predecessor, the Otto and Langen, is a one-cylinder atmospheric gas |

| MR. BryANT is associate professor of history at the Massachusetts Institute of |

| Technology. engine that crashed and clanged like a rapid-fire pile driver and must |

have been a difficult engine to live with. So the great selling point of |

Otto's engine of 1876 was that it was quiet. |

| In designing this engine Otto was aiming at the rapidly growing |

| market for small stationary power plants; he needed an engine that was |

smaller and smoother and more flexible than the noisy and awkward |

| Otto and Langen, and especially one that could be built for larger |

powers, for the atmospheric engine was limited to about three horse- |

power. In competition with the steam engine, the gas engine could |

offer superior efficiency, but it used an expensive fuel. For small pow- |

ers, though, where fuel economy was not a first consideration, it had |

the decisive advantage of easy operation and adaptability to intermit- |

tent use. A steam engine had a long warm-up period, and its fire had to |

be kept going whether the engine was working or not; it had a danger- |

ous boiler and required a full-time attendant, a license, and perhaps a |

separate structure to house the power plant and the fuel supply. The |

gas engine, on the other hand, could be started and stopped at will, it |

did not have to be fed when it was not working, and it could be safely |

installed right in a shop, with no license, no special operator, and no |

~~ fuel-storage problem if it used city gas. It was advantages like these |

that led Otto and other heroes of the development of the internal- |

combustion engine to dream of supplanting the steam engine. |

| The Silent Otto was a spectacular success. It was a sensation at the |

Paris Exposition of 1878, and within a few years it dominated the mar- |

ket for small stationary power plants. It proved to be a form of engine |

capable of development into many shapes and sizes, vertical and hori- |

zontal, large and small, with single and multiple cylinders, using gas |

or liquid fuel, and flame or hot-tube or electric ignition. Almost over- |

night the hot-air engine and the atmospheric gas engine were rendered |

obsolete, and the two-stroke engine was not a serious threat for some |

time. At the Paris Exposition of 1889, after the patents had been |

| broken in Germany and France, there were said to have been fifty types |

of engine operating on Otto’s principle. At the end of the century a |

four-cylinder engine of one-thousand horsepower was delivered,* and |

~~ there must have been one hundred thousand engines in service bearing |

~~ Otto’s name, not to mention the dozens of competing brands using the |

same principle, providing power for machine shops, breweries, printing |

presses, pumping installations, and electric-light plants.⁵

| In order to account for the sudden success of this engine let us |

| go back to the beginning of Otto’s work with engines, follow the

| course of his thought through the fifteen years of work that culminated |

| in the Silent Otto, and try to see what the breakthrough was that |

| led to an adequate solution to the problem that had been troubling

| workers on the internal-combustion engine for a generation: the prob- |

| lem of how to get a smooth flow of power out of an explosive fuel |

| burned in the working cylinder. |

| In the 1870's and the 1880’s it was not easy to say what made the

| Silent Otto silent. The question was argued in great length in courts |

| of law and in professional journals, and the most eminent experts dis- |

| agreed with each other and changed their minds. Otto thought that the

| key to his success was a special way he had of introducing fuel and air |

| into the cylinder that cushioned the shock of the explosion. The pre- |

| vailing—but not unanimous—opinion of the profession was that he was

| wrong, and even today engineers do not always agree on the desirabil- |

| ity of heterogeneous or stratified charges of the kind that Otto thought |

| he had in his engine.

| Otto was a traveling salesman without technical training in 1860 |

| when he read in the paper an enthusiastic account of a gas engine built |

| by a Frenchman named Etienne Lenoir (1822-1900). He arranged to |

| have a similar small engine built by a mechanic, started tinkering with |

| it in his spare time, and promptly ran up against the key problem that

| baffled everyone at that time: how to control an explosive fuel. |

| The Lenoir engine, which was very widely discussed in the popular |

| and the technical press in the period 1860-63, was a two-stroke, |

| double-acting affair that looked very much like a steam engine and |

| operated without compression. It sucked in a mixture of illuminating |

| gas and air, ignited it by an electric spark halfway through the stroke,

| and used the remaining half as the power stroke. On the way back the |

| piston was driven by a similar impulse on the other side. The publicity |

1 Recently, e.g. by Gustav Goldbeck in “Entwicklungsstufen des Verbrennungsmotors,” Motortechnische Zeitschrift, XXIII (1962), 76-80, and in several other articles; by Friedrich Sass in Geschichte des deutschen Verbrennungsmotorenbaues von 1860 bis 1918 (Berlin, 1962), pp. 19-74, 147-67; and by Arnold Langen in Nicolaus August Otto, der Schopfer des Verbrennungsmotors (Stuttgart, 1949). I rely heavily on Professor Sass for information about engines. I also acknowledge very helpful conversations with Dr. Goldbeck, archivist of Klockner-Humboldt-Deutz, and with Professors C. Fayette Taylor and Augustus R. Rogowski of the Massachusetts Institute of Technology.

2 Sass, p. 44; Paul Gille, “Beau de Rochas. Les trois mémoires de 1862 sur différentes conditions d’application de Iénergie,” Documents pour Pbistoire des tech- |

| niques, No. 2, p. 37; Conrad Matschoss, Geschichte der Gasmotorenfabrik Deutz |

| (Berlin, 1921), p. 55. |

184

3 Gustav Goldbeck, “Nicolas-Auguste Otto (1832-1881),” Documents pour Ibistoire des techniques, No. 1, p. 38. The year of Otto’s death is misprinted in this title. It should be 1891.

4 Sass, p. 319.

5 Matschoss, pp. 107-8.

6 For an early popular account see Alfred Darcel, “Un nouveau Moteur,”

L’Dlustration, XXXV (1860), 342-43. For a technical study see H. Tresca, “Procés-

Verbal des expériences faites sur les moteurs a gaz de M. Lenoir,” Annales du Con-

servatoire Impérial des Arts et Métiers, 1 (1861), 849-79. Articles by engineers

appearing in German journals that Otto could have seen are conveniently sum-

marized under the heading “Gaskraftmaschine” in Jabresbericht iiber die Fort-

schritte der mechanischen Technik und Technologie, 1 (1863), 111-31. “According

to Cosmos, and other French papers,” said the Scientific American (III [1860], 193),

“the age of steam is ended—Watt and Fulton will soon be forgotten. This is the way

they do such things in France.”