老天机报

2018年12月01日 22:24 来源:石家庄新闻网

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The Mongolfier type of balloon, depending on hot air for its lifting power, was soon realised as having dangerous limitations. There was always a possibility of the balloon catching fire while it was being filled, and on landing there was further danger from the hot pan which kept up the supply of hot air on the voyage—the collapsing balloon fell on the pan, inevitably. The scientist Saussure, observing the filling of the balloons very carefully, ascertained that it was rarefaction324 of the air which was responsible for the lifting power, and not the heat in itself, and, owing to the rarefaction of the air at normal temperature at great heights above the earth, the limit of ascent for a balloon of the Mongolfier type was estimated by him at under 9,000 feet. Moreover, since the amount of fuel that could be carried for maintaining the heat of the balloon after inflation was subject to definite limits, prescribed by the carrying capacity of the balloon, the duration of the journey was necessarily limited just as strictly.

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In the meantime, to avoid any possible misunderstanding, it should be stated that even after a successful test of the present great aerodrome, designed to carry a man, we are still far from the ultimate goal, and it would seem as if years of constant work and study by experts, together with the expenditure of thousands of dollars, would still be necessary before we can hope to produce an apparatus of practical utility on these lines.—Washington, January 6, 1904.

It was at the conclusion of these experiments of 1903 that the brothers concluded they had obtained sufficient data from their thousands of glides and multitude of calculations to permit of their constructing and making trial of a power-driven machine. The first designs got out provided for a total weight of 600 lbs., which was to include the weight of the motor and the pilot; but on completion it was found that there was a surplus of power from the motor, and thus they had 150 lbs. weight to allow for strengthening wings and other parts.

It was finally ascertained that the defect could be remedied by trussing down the ribs of the whole machine so as to reduce the depth of curvature. When this had been done gliding was resumed, and after a few trials glides of 366 and 389 feet were made with prompt response on the part of the machine, even to small movements of the rudder. The rest of the story of the gliding experiments of 1901 cannot be better told than in Wilbur Wright’s own words, as uttered by him in the lecture from which the foregoing excerpts have been made.

Other notable designs of these early days were the ‘R.E.P.’, Esnault Pelterie’s machine, and the Curtiss-Herring biplane. Of these Esnault Pelterie’s was a monoplane, designed in that form since Esnault Pelterie had found by experiment that the wire used in bracing offers far more resistance to the air than its dimensions would seem to warrant. He built the wings of sufficient strength to stand the strain of flight without bracing wires, and dependent only for their support on the points of attachment to the body of the machine; for the rest, it carried its propeller in front of the planes, and both horizontal and vertical rudders at the stern—a distinct departure from the Wright and similar types. One wheel only was fixed under the body where the undercarriage exists on a normal design, but light wheels were fixed, one at the extremity of each wing, and there was also a wheel under the tail portion of the machine. A single lever actuated all the controls for steering. With a supporting surface of 150 square feet the machine weighed 946 lbs., about 6.4 lbs. per square foot of lifting surface.

148 Wilbur Wright has set down the beginnings of the practical experiments made by the two brothers very clearly. ‘The difficulties,’ he says, ‘which obstruct the pathway to success in flying machine construction are of three general classes: (1) Those which relate to the construction of the sustaining wings; (2) those which relate to the generation and application of the power required to drive the machine through the air; (3) those relating to the balancing and steering of the machine after it is actually in flight. Of these difficulties two are already to a certain extent solved. Men already know how to construct wings, or aeroplanes, which, when driven through the air at sufficient speed, will not only sustain the weight of the wings themselves, but also that of the engine and the engineer as well. Men also know how to build engines and screws of sufficient lightness and power to drive these planes at sustaining speed. Inability to balance and steer still confronts students of the flying problem, although nearly ten years have passed (since Lilienthal’s success). When this one feature has been worked out, the age of flying machines will have arrived, for all other difficulties are of minor importance.

For the gliding experiments of 1901 it was decided to retain the form of the 1900 glider, but to increase155 the area to 308 square feet, which, the brothers calculated, would support itself and its operator in a wind of seventeen miles an hour with an angle of incidence of three degrees. Camp was formed at Kitty Hawk in the middle of July, and on July 27th the machine was completed and tried for the first time in a wind of about fourteen miles an hour. The first attempt resulted in landing after a glide of only a few yards, indicating that the centre of gravity was too far in front of the centre of pressure. By shifting his position farther and farther back the operator finally achieved an undulating flight of a little over 300 feet, but to obtain this success he had to use full power of the rudder to prevent both stalling and nose-diving. With the 1900 machine one-fourth of the rudder action had been necessary for far better control.

Henry Farman, to whom reference has already been made, was engaged with his two brothers, Maurice and Richard, in the motor-car business, and turned to active interest in flying in 1907, when the Voisin firm built his first biplane on the box-kite principle. In July of 1908 he won a prize of £400 for a flight of thirteen miles, previously having completed the first kilometre flown in Europe with a passenger, the said passenger being Ernest Archdeacon. In September of 1908 Farman put up a speed record of forty miles an hour in a flight lasting forty minutes.

Stringfellow’s power-driven model—the first model to achieve engine-driven flight.

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‘3. That in arched surfaces the centre of pressure at 90 degrees is near the centre of the surface, but moves slowly forward as the angle becomes less, till a critical angle varying with the shape and depth of the curve is reached, after which it moves rapidly toward the rear till the angle of no lift is found.

The Mongolfiers were undoubtedly first to send up balloons, but other experimenters were not far behind them, and before they could get to Paris in response to their invitation, Charles, a prominent physicist of those days, had constructed a balloon of silk, which he proofed against escape of gas with rubber—the Roberts had just succeeded in dissolving this320 substance to permit of making a suitable coating for the silk. With a quarter of a ton of sulphuric acid, and half a ton of iron filings and turnings, sufficient hydrogen was generated in four days to fill Charles’s balloon, which went up on August 29th, 1783. Although the day was wet, Paris turned out to the number of over 300,000 in the Champs de Mars, and cannon were fired to announce the ascent of the balloon. This, rising very rapidly, disappeared amid the rain clouds, but, probably bursting through no outlet being provided to compensate for the escape of gas, fell soon in the neighbourhood of Paris. Here peasants, ascribing evil supernatural influence to the fall of such a thing from nowhere, went at it with the implements of their craft—forks, hoes, and the like—and maltreated it severely, finally attaching it to a horse’s tail and dragging it about until it was mere rag and scrap.

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In the meantime, to avoid any possible misunderstanding, it should be stated that even after a successful test of the present great aerodrome, designed to carry a man, we are still far from the ultimate goal, and it would seem as if years of constant work and study by experts, together with the expenditure of thousands of dollars, would still be necessary before we can hope to produce an apparatus of practical utility on these lines.—Washington, January 6, 1904.

The final trial of the Langley aerodrome was made on December 8 th, 1903; nine days later, on December 17th, the Wright Brothers made their first flight in a power-propelled machine, and the conquest of the air was thus achieved. But for the two accidents that spoilt his trials, the honour which fell to the Wright Brothers would, beyond doubt, have been secured by Samuel Pierpoint Langley.

‘The planes were staid from three sets of fish-shaped masts, and rigged square and firm by flat steel rigging. The engine and boiler were put in the car to drive two screw-propellers, right and left-handed, 3 ft. in diameter, with four blades each, occupying three-quarters of the area of the circumference, set at an angle of 60 degrees. A considerable time was spent in perfecting the motive power. Compressed air was tried and abandoned. Tappets, cams, and eccentrics were all tried, to work the slide valve, to obtain the best results. The piston rod of engine passed through both ends of the cylinder, and with long connecting rods worked direct on the crank of the propellers. From memorandum of experiments still preserved the following is a copy of one: June, 27th, 1845, water 50 ozs., spirit 10 ozs., lamp lit 8.45, gauge moves 8.46, engine started 8.48 (100 lb. pressure), engine stopped 8.57, worked 9 minutes, 2,288 revolutions, average 254 per minute. No priming, 40 ozs. water consumed, propulsion (thrust of propellers), 5 lbs. 4? ozs. at commencement, steady, 4 lbs. ? oz., 57 revolutions to 1 oz. water, steam cut off one-third from beginning.

‘2. That the ratio of drift to lift in well-shaped165 surfaces is less at angles of incidence of 5 degrees to 12 degrees than at an angle of 3 degrees.

‘The planes were staid from three sets of fish-shaped masts, and rigged square and firm by flat steel rigging. The engine and boiler were put in the car to drive two screw-propellers, right and left-handed, 3 ft. in diameter, with four blades each, occupying three-quarters of the area of the circumference, set at an angle of 60 degrees. A considerable time was spent in perfecting the motive power. Compressed air was tried and abandoned. Tappets, cams, and eccentrics were all tried, to work the slide valve, to obtain the best results. The piston rod of engine passed through both ends of the cylinder, and with long connecting rods worked direct on the crank of the propellers. From memorandum of experiments still preserved the following is a copy of one: June, 27th, 1845, water 50 ozs., spirit 10 ozs., lamp lit 8.45, gauge moves 8.46, engine started 8.48 (100 lb. pressure), engine stopped 8.57, worked 9 minutes, 2,288 revolutions, average 254 per minute. No priming, 40 ozs. water consumed, propulsion (thrust of propellers), 5 lbs. 4? ozs. at commencement, steady, 4 lbs. ? oz., 57 revolutions to 1 oz. water, steam cut off one-third from beginning.

Stringfellow’s power-driven model—the first model to achieve engine-driven flight.

Thus speaks the inventor; the cold official mind gives out a different account, crediting the ‘Avion’ with merely a few hops, and to-day, among those who consider the problem at all, there is a little group which persists in asserting that to Ader belongs the credit of the first power-driven flight, while a larger group is equally persistent in stating that, save for a few ineffectual hops, all three wheels of the machine never left the ground. It is past question that the ‘Avion’ was capable of power-driven flight; whether it achieved it or no remains an unsettled problem.

First flight of first power-driven machine, 17th December, 1903, near Kill Devil Hill, Kitty Hawk, N.C. Starting rail on left. Orville Wright piloting machine.

‘The causes of these troubles—too technical for explanation here—were not entirely overcome till the end of September, 1905. The flights then rapidly increased in length, till experiments were discontinued after October 5, on account of the number of people attracted to the field. Although made on a ground open on every side, and bordered on two sides by much-travelled thoroughfares, with electric cars passing every hour, and seen by all the people living in the neighbourhood for miles around, and by several hundred others, yet these flights have been made by some newspapers the subject of a great “mystery.”’

The publication of the patent attracted a great amount of public attention, and the illustrations in contemporary journals, representing the machine flying over the pyramids and the Channel, anticipated fact by sixty years and more; the scientific world was divided, as it was up to the actual accomplishment of flight, as to the value of the invention.

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