The Origin of the Four-Stroke Cycle
By Lynwood Bryant
Professor BRYANT of the Massachusetts Institute of Technology has done much research on the origins and development of the internal-combustion engine.
In an earlier paper1 on the genesis of a gas engine built by Nicolaus August Otto in 1876, I tried to follow the course of Otto’s thought and to explain the success of his engine. Otto attributed his success to what he called the stratified charge, a special way he devised of mixing the fuel and air in his cylinder. His theory was wrong, but guided by this theory he built a remarkably successful and influential engine, the earliest recognizable ancestor of today’s automobile engine.
I should now like to argue that Otto’s engine of 1876 was the first to use the four-stroke cycle. The four-stroke process, which first made it practical for a gas engine to use compression, was a key idea in the evolution of the internal-combustion engine, and the question of priority in its use was once a matter of critical importance: fortunes were at stake, or at least the owners of the patents involved thought so. Now the patents and the inventors are dead, and all that is at stake is credit for the invention. But the historical literature on early engines still reflects the confusion and disagreement of the old patent litigation, and perhaps it would be a service to review and evaluate the competing claims now that no money is at stake.
Four men are said to have used the four-stroke cycle before 1876. All of these claims arose in the course of patent litigation from ten to forty years after the time of the invention, and they all still appear from time to time in the literature. None is supported by substantial contemporary evidence. In 1862, the French engineer Beau de Rochas expressed the idea of the four-stroke cycle, but there is no evidence that he built an engine of this type or had any influence on anybody who did. The Munich watchmaker Reithmann and the famous Viennese inventor Marcus both were followers and not predecessors of Otto with their four-stroke engines. And the claim that Otto himself used the four-stroke process in an experimental engine in 1862 rests on extremely slight contemporary evidence. I conclude that primary credit for the invention of the four-stroke cycle should go to Otto, and that the invention should be dated 1876.
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- “The Silent Otto,” Technology and Culture, VII (Spring 1966), 184-200.