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of Kitty Hawk | Part IX By Walter T. Bonney
Copyright, 1956, by Fairchild Engine and Airplane Corporation

THEY called them explosion engines in the earliest days.  And so, in a sense, they are, machines in which energy is translated directly into mechanical power by causing a fast rate of burning behind a piston within a cylinder.  Wilbur and Orville Wright used such an engine for their first flights, and for the next 36 years (until the advent of the turbojet engine in 1939) all powered, heavier-than-air flight depended upon man's development of this prime mover - the internal combustion engine. 

As early as 1680, Christian Huygens, the remarkable Dutch mathematician and physicist, worked out the practical details of an internal combustion engine - to be fueled by gunpowder.  A century later, Street proposed an engine driven by a flame-ignited explosive mixture of vaporized turpentine and air, and in 1838 Barnett provided the vital improvement of compressing the explosive charge prior to ignition.  Despite Sir George Cayley's suggestion in 1810 that such engines be harnessed to propel aircraft (Prelude to Kitty Hawk, Chap. II), nearly a century of further development was required before the internal combustion engine was transformed from a ponderous machine - turning over at little more than 200 rpm., and weighing a thousand pounds of more for each horsepower of work performed - into a powerplant sufficiently light and reliable to make possible powered, heavier-than-air flight. 

It was not until the 1860's when Lenoir built his first useful, though crude, gas-fueled internal combustion engines that this type of power plant really began to mature.  In 1862, Beau de Rochas stated explicitly the principle of the four-stroke cycle:- 1, Drawing the fuel and air into the cylinder by suction during the first down stroke of the piston;  2, compressing the gaseous fuel mixture during the first up stroke;  3, ignition of the compressed charge and expanding the exploded gases during the second down stroke, and 4, discharge of the burned gases during the second up stroke.  Fourteen years later, Otto built his first de Rochas 4-cycle engine.  It and others Otto built were so successful that in later years this became the most common type among the internal combustion engines and often was known as the Otto cycle.

Among the first to work determinedly and effectively at the task of reducing the weight of the internal combustion engine and of increasing the power output by speeding up its operations were the Germans, Gottlieb Daimler and Karl Benz.  In 1886, Daimler built a gasoline-fueled engine that, at least by the standards of his day, was both light and fast - it weighed 88 pounds-per-horsepower and ran at 800 rpm.  His first tricycle - a three-wheeled, road-runner that preceded the four-wheeled automobile and the two-wheeled motorcycle - was built in 1886, and his first automobile the following year.

Benz also constructed small engines for tricycle use about the same time. In 1889, the only automobile displayed at the Paris exhibition was powered by a Benz motor.  In 1889, Daimler made arrangements with Panhard and Levassor for manufacture of his engines in France, and rapid development of the motor car in that country may be said to have been fairly started as a result.

Another of the pioneering engine manufacturers was the de Dion-Bouton firm, which used a high tension magneto ignition system on high-speed engines (1500-1800 rpm.) that produced large powers.  The original de Dion-Bouton engines were air-cooled, with finned cylinders, and had aluminum crankcases.

The first internal combustion engine used for aerial application was of the Lenoir type.  It was built in 1872 to power Paul Haenlein's airship in Germany.  A 4-cylinder, five horsepower engine, it ran at only 40 rpm., and consumed about 250 cubic feet per hour of gas taken from the balloon itself.  In 1897, Daimler engines were installed in the unsuccessful airships built by Schwarz, and by Baumgarten and Wolfert.  There was insufficient interest in airship construction in the years just before and after the turn of the century to warrant the heavy expense of developing a really light-weight engine.  Nor was the growing motor car industry enough concerned with weight reduction to produce the kind of power plant the would-be aviators needed.

When Prof. Samuel P. Langley (Prelude to Kitty Hawk, Chap. IV) began searching in 1900 for someone in Europe to build a lightweight engine for his airplane he did so only after an American manufacturer had failed in a year-long effort to construct a 12-hp. engine not more than 100 lb. in weight.  Charles Manly, Langley's assistant, canvassed French motor makers without success.  Albert de Dion told him that the engine he wanted was quite out of the question.  If anyone could build it, he, de Dion could.  Since he could not, it was obviously an impossible project!  And yet, with the urge to fly so compelling on both sides of the Atlantic, something had to be done about providing suitable engines.  First came Manly's remarkable radial engine, then the Wright brothers built their light, simple adaptation of the automobile engine, and finally, brilliant engineers, especially in Europe, produced a whole family of internal combustion engines, some of them excellent producers of power, for aircraft propulsion.

Between 1900 and the beginning of World War I, most of the basic design possibilities for aircraft use of the internal combustion engine were investigated, at least to the extent of experimental construction.  There were vertical types and vee-types, radials and rotaries, and horizontally opposed engines.  Both carburetion, in many variants, and direct fuel injection were used.  Yes, those were years of vigorous, fruitful aircraft engine development.  If many of the earliest designs failed for lack of suitable structural materials and manufacturing techniques, the experience of the engine makers was no different from that in many fields of endeavor - including that involving the design and construction of airframes.  Charles

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