THE FLYING MACHINES OF MAXIM AND LANGLEY
At the same time that Lilienthal was making his initial experiments, another champion of the same school of aviators was achieving equally successful results along somewhat different, and yet on the whole, similar lines. Sir Hiram Maxim, the inventor of so many destructive types of guns, was devoting much time and energy to the construction of a flying-machine. His apparatus was of the aeroplane type, but unlike that of Lilienthal, Chanute, or Hering, was to be propelled by steam-driven screw-propellers. Nor was the apparatus he proposed to make a diminutive affair weighing a few pounds and capable of lifting only the weight of a man. His huge machine weighed in the neighborhood of four tons and carried a steam-engine that developed some three hundred and sixty horse-power in the screws. It was two hundred feet in width, and mounted on a car track, along which it was to be run to acquire the necessary initial velocity before mounting into the air.
On July 31, 1894, this huge machine started on a trial spin, carrying a crew of three persons, besides fuel and water for the boilers. When a speed of thirty-six miles an hour on the track had been acquired, the apparatus lifted itself in the air, and sailed for some distance, a maximum flight of over three hundred feet finally being made. This experiment demonstrated several important things—in fact, solved "three out of five divisions of the problem of flight," as Lord Kelvin declared. It demonstrated that a flying-machine carrying its own propelling power could be made powerful and light enough to lift itself in the air; that an aeroplane will lift much more than a balloon of equal weight; and that a well-made screw-propeller will grip the air sufficiently to propel a machine at a high rate of speed.
Since the two remaining divisions of the five concerned in the problem of flight had been already solved by Lilienthal, it seemed that it only remained for some scientist to combine this complete knowledge in the proper way to produce a practical flying-machine—one that would fly through the air, and continue to fly until the power was exhausted. It was not a startling announcement to the scientific world, therefore, when about three years later the news was flashed that Prof. S. P. Langley had produced such an apparatus.
FLYING MACHINES OF THE MONOPLANE TYPE.
Upper figure, the aeroplane of M. Robert Esnault-Pelterie. Middle figure, the aeroplane of M. Blériot. Lower figure, the Vuia aeroplane, a bat-like machine of freakish structure which had no large measure of success. A modification of the boat-like machine shown in the upper figure gained celebrity through its use by M. Latham in the first attempt (in July, 1909) to fly across the English Channel. M. Blériot's aeroplane as finally developed became a very successful flying machine. With its aid M. Blériot was first to accomplish the feat of flying across the English Channel (from Calais to Dover in about 23 minutes) on the morning of July 25th, 1909. These pictures are reproduced from the London Graphic of January 25th, 1908.
Professor Langley described this really wonderful machine, which he called the "aerodrome," as follows:
"In the completed form there are two pairs of wings, each slightly curved, each attached to a long steel rod which supports them both, and from which depends the body of the machine, in which are the boilers, the engines, the machinery, and the propeller wheels, these latter being not in the position of an ocean steamer, but more nearly amidships. They are made sometimes of wood, sometimes of steel and canvas, and are between three and four feet in diameter.
"The hull itself is formed of steel tubing; the front portion is closed by a sheathing of metal which hides from view the fire-grate and apparatus for heating, but allows us to see a little of the coils of the boiler and all of the relatively large smokestack in which it ends. There is a conical vessel in front which is simply an empty float, whose use is to keep the whole from sinking if it should fall in the water.
"This boiler supplies steam for an engine of between one and one-half horse-power, and, with its fire-grate, weighs a little over five pounds. This weight is exclusive of that of the engine, which weighs, with all its moving parts, but twenty-six ounces. Its duty is to drive the propeller wheels, which it does at rates varying from 800 to 1,200, or even more, turns a minute, the highest number being reached when the whole is speeding freely ahead.
"The rudder is of a shape very unlike that of a ship, for it is adapted both for vertical and horizontal steering. The width of the wings from tip to tip is between twelve and thirteen feet, and the length of the whole about sixteen feet. The weight is nearly thirty pounds, of which about one-fourth is contained in the machinery. The engine and boilers are constructed with an almost single eye to economy of weight, not of force, and are very wasteful of steam, of which they spend their own weight in five minutes. This steam might all be recondensed and the water re-used by proper condensing apparatus, but this cannot be easily introduced in so small a scale of construction. With it the time of flight might be hours instead of minutes, but without it the flight (of the present aerodrome) is limited to about five minutes, though in that time, as will be seen presently, it can go some miles; but owing to the danger of its leaving the surface of the water for that of the land, and wrecking itself on shore, the time of flight is limited designedly to less than two minutes."
When this flying-machine was put to the actual test its performance justified the most sanguine expectations; it actually flew as no other machine had ever flown before. A number of men of science watched this remarkable performance, among others Alexander Graham Bell, the inventor of the telephone, who reported it to the Institute of France. "Through the courtesy of Mr. S. P. Langley, Secretary of the Smithsonian Institution, I have had on various occasions the pleasure of witnessing his experiments with aerodromes," wrote Dr. Bell, "and especially the remarkable success attained by him in his experiments made on the Potomac River on Wednesday, May 6th [which led me to urge him to make public some of these results].
"On the occasion referred to, the aerodrome, at a given signal, started from a platform about twenty feet above the water, and rose at first directly in the face of the wind, moving at all times with remarkable steadiness, and subsequently swinging around in large curves of, perhaps, a hundred yards in diameter, and continually ascending until its steam was exhausted, when at a lapse of about a minute and a half, and at a height which I judged to be between eighty and one hundred feet in the air, the wheels ceased turning, and the machine, deprived of the aid of propellers, to my surprise did not fall, but settled down so softly and gently that it touched the water without the least shock, and was in fact immediately ready for another trial."
To most persons, even to the cautious and scientific inventor himself, the performance of this, and a second aerodrome which flew about three-quarters of a mile, seemed to show that the secret of aerial navigation was all but fathomed. "The world, indeed, will be supine," Langley wrote a short time after the success of his flying-machine, "if it does not realize that a new possibility has come to it, and that the great universal highway overhead is soon to be opened." What could be plainer? A machine of a certain construction, weighing some thirty pounds, and carrying at that some excess of weight, had been able to fly a relatively long distance. What easier than to construct a machine on precisely similar lines only ten, a hundred, a thousand times larger, until it would carry persons and cargo, and fly across an ocean or a continent?
Professor Langley himself, as was most fitting, undertook the construction of such a man-carrying air-ship. And it was during this undertaking that he made the momentous discovery that seemed to oppose a question mark to the possibility of flight by the aeroplane principle. This discovery was an "unyielding mathematical law that the weight of such a machine increases as the cube of its dimensions, whereas the wing surface increases as the square." In other words, as the machine is made larger, the size of the wings must be increased in an alarmingly disproportionate ratio. And the best that Professor Langley's man-carrying flying-machine could do, after the inventor had expended the limit of his ingenuity, was to dive into the waters of Chesapeake Bay, instead of soaring through the air as its prototype, the aerodrome, had done.