Nikolaus August Otto

German inventor

• Born: June 10, 1832
• Birthplace: Holzhausen, Nassau (now in Germany)
• Died: January 26, 1891
• Place of death: Cologne, Germany

Otto invented the first internal combustion, four-stroke engine that was the forerunner of the modern gasoline automobile engines that transformed world transportation during the twentieth century.

Early Life

Nikolaus August Otto was born in a small German village on the banks of the Rhine River. His father, postmaster and innkeeper in the village, died shortly after his birth. As a child, he was bright and did well in school, and his mother wanted, at first, to enter her son in higher education. The unrest of 1848 changed her mind, however, and she decided that the business world would provide a better future for him. Accordingly, he gave up high school (where he had been a star student) and went to work.

Otto’s first job was as a clerk in a small-town grocery store. From there he moved to a job as a clerk in Frankfurt, and eventually became a traveling salesperson for a wholesale grocer, working out of Cologne. In 1860, still a traveling salesperson, Otto read a newspaper account of a gas engine built by a Frenchman, Étienne Lenoir . The Lenoir engine was well known at this time, and Otto studied it carefully. As the piston of the Lenoir engine moved down the cylinder, it drew in a mixture of gas and air. An electric spark ignited the air/gas mixture halfway through the stroke, creating the power necessary to push the piston to the bottom of the cylinder. Each piston was doubled-sided, so the piston returned to its original position when the same steps were repeated on the opposite side. It is important to note that this engine did not compress the air/gas mixture and that it relied on illuminating gas (used in homes and street lamps) for its fuel. Lenoir had trouble getting it to run smoothly under a load.

Life’s Work

With strong links to rural regions both in his boyhood and in his job, Otto was bothered by the fact that the Lenoir engine relied on a fuel that was available only through a system of pipelines found in the cities. He saw that the internal combustion engine had the potential to become an important source of power in a wide variety of applications, and he determined to make an engine that could be used in city and village alike. He devised a carburetor for the Lenoir engine that enabled the engine to receive fuel from a tank rather than a pipeline. Although his patent application for the carburetor was rejected, he continued to work on the internal combustion engine.

In 1861, Otto commissioned Michael Zons, an instrument maker and machine-shop owner in Cologne, to build a Lenoir engine. Otto studied this engine carefully in an attempt to make it run smoothly under a load. The main problem with the engine was the shock of detonation on the piston. While he was experimenting with this engine, Otto stumbled across a phenomenon that would later pay him great dividends. He drew in the air/gas charge and then, instead of allowing the piston to continue down the cylinder, he moved it back up toward the cylinder head, compressing the charge. Otto was surprised to find that the detonation was so violent as to turn the engine through several revolutions. This was the principle upon which he would later base the four-stroke cycle. After continued experimentation with the Lenoir engine, Otto decided that the difficulties were too great and turned to a new type of engine: the atmospheric engine.

The atmospheric engine resembled an upward-pointing cannon with gears and levers attached. As the motion of the flywheel pulled the piston up, air and gas were drawn in beneath the piston. At the same time, the piston pushed the air above it out of the cylinder and into a tank, where it was stored at above-atmospheric pressure. The combustion of the air/gas mixture pushed the piston up at high velocity to the top of the cylinder, creating a vacuum in the cylinder below the piston. The piston’s own weight and the pressure difference between the air in the holding tank and the vacuum in the cylinder then returned the piston to the bottom of the cylinder.

Zons built a one-half horsepower model of the atmospheric engine for Otto in 1863. In order to develop the engine, Otto obtained financial backing from Eugen Langen, son of a wealthy industrialist, and they entered into a formal business agreement in March of 1864. With Langen’s help, Otto refined the atmospheric engine. After three years of work, the Otto and Langen engine was shown at the 1867 Paris Exposition, winning the grand prize. Having built a successful engine, Otto and Langen now needed to manufacture and sell their product. They found more capital, created the Gasmotorenfabrik Deutz corporation in 1872, and shortly thereafter were selling their engines around the world.

The Otto and Langen engine proved to be popular; five thousand were eventually built. The engine’s reliance on atmospheric pressure (the final version did not have the holding tank for air) posed a serious limitation, however, by limiting its output to a maximum of three horsepower. Furthermore, it was extremely noisy and vibrated strongly when in operation. In response to these shortcomings, Otto began to think about a new type of engine (possibly reviewing his earliest experiments with the Lenoir engine) in which the air/gas mixture was compressed in the cylinder before ignition. The engine then used one stroke each for the intake, compression, ignition (and expansion), and exhaust functions. In such an engine there was only one power stroke for every four piston strokes, hence the name “four-stroke cycle.” This was a bold step, considering that the double-acting steam engine—the dominant power technology of the time—used each stroke as a power stroke.

Otto was concerned that detonation of the compressed air/gas mixture would produce a violent explosion capable of damaging the engine. To lessen the shock of detonation, he devised a concept known as the “stratified charge,” in which the richest mixture would be farthest from the piston, with successive layers of air and exhaust gases filling the remainder of the cylinder. Otto believed that this would create a gradual burning instead of a violent explosion. The stratified charge was so important to Otto that it constituted the main claim in his patent, rather than the four-stroke cycle or the compressed charge.

Otto built the first of these engines in 1876 at the Gasmotorenfabrik Deutz works. Even the rough prototype demonstrated the many advantages of the four-stroke engine to Otto and his partners. Compared to the atmospheric engine (and others of the time) the four-stroke engine produced, for the same displacement and engine weight, far more horsepower. In addition to erasing the three-horsepower ceiling of the atmospheric engine, the new engine operated with much less noise and vibration, earning the nickname “Silent Otto.” Gasmotorenfabrik Deutz refined the prototype and eventually marketed the engine with great success. By the turn of the century, Otto’s firm had built twenty-four thousand engines.

In 1882, the first of several claims against Otto’s patent rights arose. He was to spend the rest of his life defending himself against these claims. The most damaging came from a competitor who wanted to void Otto’s patent on the four-stroke cycle on the basis of an obscure pamphlet written in 1862 by the French engineer Alphonse-Eugène Beau de Rochas. Rochas had clearly stated the principles of the four-stroke cycle in his pamphlet, but apparently he never realized its significance and never built an engine operating on those principles. Nevertheless, in 1886 Otto lost his German patents on the four-stroke cycle. He considered the patent suits an attack upon his honor, and the defeat in 1886 left him an embittered man. The legal battle continued until 1890, when the last appeal ended. On January 26, 1891, Nikolaus Otto died of heart failure in Cologne.

Significance

Automobiles using Nikolaus August Otto’s engine appeared on the roads of Europe only ten years after he built the prototype, and less than two decades later the Wright brothers’ aircraft was propelled by a four-stroke engine. The predominant type of automobile engine in the twenty-first century is a direct descendant of Otto’s 1876 engine. One asset of Otto’s engine is its flexibility, thanks to its small size, low weight, and the multitude of possible configurations (vertical, horizontal, single or multiple cylinders, ability to run on many kinds of fuels, and the like). Although Otto placed more faith in the stratified-charge concept than was probably warranted, he did, nevertheless, build the first successful engine to operate on the four-stroke cycle. For his persistence in solving the problems he encountered and for seeing them through to their respective solutions, he deserves the credit as that engine’s inventor.

Bibliography

Bryant, Lynwood. “The Origin of the Automobile Engine.” Scientific American 216 (March, 1967): 102-112. This article concentrates on the intellectual process by which Otto arrived at the 1876 engine. Bryant notes that Otto believed in the stratified charge to the end, although most other experts believed that the charge should be as homogeneous as possible. The many illustrations and photographs are a great help in understanding the technical details of Otto’s engines. No documentation.

‗‗‗‗‗‗‗. “The Origin of the Four-Stroke Cycle.” Technology and Culture 8 (April, 1967): 178-198. Examines Otto’s claim to inventing the four-stroke cycle. In a carefully documented and reasoned argument, Bryant shows that while others had the idea of a four-stroke cycle, credit for invention should go to Otto. The section on Rochas, the cause of much grief to Otto, is of special interest.

‗‗‗‗‗‗‗. “The Silent Otto.” Technology and Culture 7 (Spring, 1966): 184-200. Asks why Otto was successful after so many others had been trying to assemble an internal combustion engine for seventy-five years. Traces his thought through fifteen years of development; points out that only in 1876, having gained much practical experience, was Otto ready to accept the four-stroke cycle he had discovered accidentally in 1862. In addition to the usual sources, Bryant has assembled evidence directly from the patent records.

Csere, Csaba. “Nikolaus Otto and His Remarkable Compression Stroke.” Car and Driver 39, no. 8 (February, 1994): 7. Describes some of Otto’s designs for the four-stroke cycle engine; explains his partnership with Eugen Langen.

Cummins, C. Lyle, Jr. Internal Fire. Lake Oswego, Oreg.: Carnot Press, 1976. Written by the son of the founder of the Cummins Engine Company, this book is an absorbing account of the internal combustion engine from the seventeenth century to the present. Chapters 8 and 9 deal specifically with Otto. Cummins is not afraid to differ with other historians and generally provides good support for his arguments.

Goldbeck, Gustav. “Nikolaus August Otto, Creator of the Internal-Combustion Engine.” In From Engines to Autos: Five Pioneers in Engine Development and Their Contributions to the Automotive Industry, by Eugen Diesel, Gustav Goldbeck, and Friedrich Schilderberger. Chicago: H. Regnery, 1960. Goldbeck recounts the highlights of Otto’s life and his accomplishments in the development of his engine. Lacks documentation but appears reasonably accurate. Is less sterile than many sources in that Goldbeck tries to reveal a more human side to the successes and failures Otto experienced.

Grayson, Stan. Beautiful Engines: Treasures of the Internal Combustion Century. Marblehead, Mass.: Devereux Books, 2001. Chapter 2 in this illustrated history of the internal combustion engine describes Otto’s engine.

Karwatka, Dennis. “Technology’s Past.” Tech Directions 61, no. 8 (March, 2002): 10. Describes how Otto created his four-stroke cycle engine.