The Rotary Is Here And

THE ROTARY (S HERE NOAND W By Patrick Frers (EAA 16476) may lead you to seek a more comprehensive insight into 108 Guatay Ave. this marvelous powerplant through available litera- Chula Vista. CA 92011 ture. A CONDENSED HISTORY OF THE WANKEL It all started with some very old basic concepts pre- O'N, E THING THAT has kept me puzzled is the fact viously used in the development of the rotary valve sys- that our community of aircraft homebuilders has not tem and the positive displacement pump. On February 1, as yet "discovered" the Wankel rotary engine, with its 1957 Dr. Felix Wankel succeeded in test running a many extraordinary advantages over the type of recipro- "motorized" version of these systems, the culmination cating engines commonly favored for aircraft use. of a research program supported by N.S.U. in Germany. Alternatives to certified aircraft engines are being This rudimentary but ingenious machine, vaguely re- used in increasing numbers, but their selection seems sembling today's successful rotary engine at least proved to be based on whether they "look" like the typical air- for the first time the feasibility of an engine with the craft engine rather than on the basis of dependability, simplicity of a valveless two-stroke without its draw- endurance, simplicity and economy of overhaul — char- backs, promising the realization of a dream of a futuris- acteristics of the rotary that cannot be touched by more tic powerplant with a minimum of moving parts and ex- "conventional" engines. treme reliability. It was a beautiful dream . and the The neglect of the rotary can no longer be laid to most beautiful part is that today it is a total reality!! availability . new and used automotive units can be Shortly after the initiation of work with develop- bought almost anywhere in the country. Replacement mental models, another inspired scientist made an im- parts are as close as the nearest auto dealerships. Cost portant contribution to the study. Professor Othmar is not a valid argument against the Wankel as it is now Baier of the Technical College of Stuttgart demonstrat- more or less competitive with other mass produced en- ed theoretically that the shape of the new engine's com- gines of roughly the same horsepower. Maintenance bustion chamber, arrived at empirically by Dr. Wankel, and overhaul costs can't be factors either because with was in effect and epitrochoid. This paved the way to mathe- its fewer internal parts, the Wankel is cheaper to bring matical analysis for the development of the engine. Dr. back to "like new" condition than other types. Wankel started off working on the assumption that rather than in a reciprocating piston, it was in the THE INERTIA EFFECT smoother and more "logical" motion of a "rotating piston" turning within an epitrochoid envelope that the Perhaps one of the probable causes keeping us from promise of a realistic combination of displacement and "discovering" the rotary engine is that well known "in- useful compression ratios existed for an engine for the ertia" effect (something between "persistence of set" future. and "functional fixedness", as known in human psy- After several developmental changes, the engine chology). As applied in this case . we continue using as we know it today, began to take shape and by as late something just because we've been doing it for so long as 1960 one of the models successfully endured a 1000 before, or simply "because it's commonly used", thus ig- hour test at N.S.U.; and then another 1400 hour test noring possible better alternatives. in 1963. As the many problems were inexorably con- We may even "know" that there is something better, quered, one after the other, finally the most persistent but when the time to make a decision arrives, we seem of all — apex seal durability — was solved, too. Proto- to be "conditioned" to choose the "common, usual" choice type engines ran routine tests of 1000 hours without as long as it seems adequate . not necessarily the best. problems, and consumption came down to rates com- The fostering of progress has always been out of the parable to those of reciprocating four-stroke engines reach of those who do not dare to be different, be them- (0.57 Ib./hr./hp at 5000 rpm and 0.5 at 2000 rpm in 1964 selves, think for themselves. tests). This "inertia" effect is a fact in human psychology, In the meantime, of all the firms holding a license and it often takes independent thinking to break away agreement, Toyo Kogyo of Hiroshima, Japan (Mazda) from it ... and, of course, the information and knowl- proved to be one of the most impressively active and edge to found the break upon. successful by developing a highly remarkable version But most "home-builders" are "home-builders" pre- of the Wankel rotary combustion engine in a relatively cisely because of their individualistic independence of short time. Ironically, they had initially been very coldly thinking and acting. Therefore, it could very well be received by N.S.U. and, in fact, had achieved a license that lack of familiarity with the Wankel is what is keep- only through the friendly mediation of the then Ambas- ing us from its advantages. sador of the Republic of West Germany to Japan, Dr. Then, perhaps, the brief information presented here Wilhelm Haas. This was in 1961 — only two years after SPORT AVIATION 59 engines. (The single rotor N.S.U. Spider had been in- troduced in 1964 as an exploratory move but was dis- continued in 1967.) It was not until 1969 that the first Wankel cars ap- peared on the American market in quantity with the introduction of the Mazda 100. Today, the dual ignition Mazdas still are the only rotaries widely available, but after 7 years we have a reasonable abundance of engines in the used market — the internal combustion engine of the future ready to power our airplanes now with greater dependability and financial economy than can be offered by any reciprocating piston engine in the moderate power category. A sad and ironic commentary on the American in- dustrial picture is the fact that the very first Wankel licensing agreement was issued to the Curtiss Wright Corporation in 1958. This company developed its own versions of the engine, the two rotor RC2-60 of 180 hp for automotive use and a more sophisticated aircraft en- OIL PUMP , , gine. Although possessed of definite and proven advan- (O.u l.ur.0 01.... t <.!»•») k,C3T__J ] tages over conventional engines, none have been put into production. In 1970 General Motors reluctantly en- tered as a "late comer" in the Wankel race and, as of this writing, is still thinking about the possible use of the engine. However, if figures published in 1972 are any indication, GM's cast iron engines will be of little A Wankel Engine Longitudinal Section use to homebuilders — a 160 hp engine (at 6500 rpm) (Two-Rotor Mazda) weighing 350 pounds and a 200 hp engine weighing 440 pounds. (By comparison, the good old aluminum block Olds V-8 215 weighs about 315 pounds and produces 185 hp.) So what's new in Detroit? The emphasis, as always, seems to be on cheapness. They may still manage to turn an inherently light, reliable and efficient engine into a heavy, reliable, clumsy one. When they will ever learn the lesson of lightness from foreign industry is anyone's guess. OPERATION The Wankel rotary combustion engine utilizes the same principle of internal combustion as demonstrated by Dr. Nicholas Otto in 1878 with his first working model ofa reciprocating engine . the well known "Otto Cycle", intake, compression, combustion and exhaust. There the similarity with the reciprocating engine ends. While in the reciprocating engine the combustion ac- celerates the piston in one direction at an average speed of 3000 ft. per minute, only to stop at the end of the few inches of the "stroke" run, and reverse its motion in the opposite direction, then stop again and reverse, and so on, several thousands times per minute ... in the ro- A Wankel Engine Cross-Section tary engine the so-called "piston" is rather a rotor that (Two-Rotor Mazda) doesn't waste the energy of its inertia constantly revers- ing its motion. Instead it "rotates", propelled by the news of the Wankel had reached Hiroshima. expanding gases of the combustion, always in the same Mr. Tsuneji Matsuda, president of Toyo Kogyo, made direction. Mr. Kenichi Yamamoto manager of the Rotary Engine The fundamentals of this operation can be better Development Division and in record time one of the most understood by observing Figure 1. modern and computerized development laboratory plants Since the relative position of the rotor within its was working at an extremely accelerated development housing opens and closes the intake and exhaust ports, effort. the rotor and its housing by themselves become their By 1964 Toyo Kogyo was ready to show two of its own "positive" valve system with a precise and invariable versions of the Wankel, a two rotor and a four rotor, at timing, better even than that ofa four stroke engine with the llth Tokyo Motor Show. Their first production car, its elaboration and power robbing friction. The rotor the Cosmo Sport 110-S, was completed that year and was is always timed, it doesn't burn or have to be main- shown to the public for the first time at the 1966 Tokyo tained or replaced. It also eliminates the inadequacies Motor Show. It had a two-rotor engine that produced of the absence of valves as in the two-stroke engine.

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