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.® |

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 dif- |

| férentes 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 |