In 1871 M. A. Penaud produced the interesting toy aëroplane shown in Fig. 32. The model is propelled horizontally forward by a single screw, actuated by twisted rubber, and is fastened, as shown, to the middle of a long stick or backbone. The center of mass of the machine is well to the front, tending to plunge the model earthward like a heavy-headed arrow; but this down-diving is promptly checked by the tiny rudder which is so inclined as to counteract the diving proclivity. That is to say the rudder dips so as to receive the aërial impact on its upper surface; which impact increases with the speed of flight and causes the bow to rise, until the weight before the wings just balances the impact on the rudder at the rear. The equilibrium is thus automatic, on the principle expounded by Sir George Cayley sixty years earlier. This quaint little bird when liberated in the Garden of the Tuileries flew a distance of 131 feet in eleven seconds, much to the delight of some members of the French Society for Aërial Navigation. It may be added that Penaud, who was a most promising and clever aëronautical inventor, contemplated a twin-screw monoplane large enough to carry two men, but died in his early manhood, before the project could be realized.
Fig. 33.—Tatin’s Aëroplane Model, 1879.
In 1879 M. Victor Tatin made some very promising tests with the model shown in Fig. 33, so promising, in fact, as to convince many that human flight was even then practicable. This little flyer was a twin-screw monoplane mounted on wheels, and actuated by an oscillating compressed air engine, the whole machine weighing 3.85 pounds, and supported by a silk plane measuring 16 by 75 inches. The central body of the aëroplane was a thin steel tube three feet long by four inches in diameter containing the compressed air, and weighing only one pound and a half, though strong enough to endure a pressure of twenty atmospheres. When the model was allowed to run round a board walk 46 feet in diameter, tethered to a stake at the center, it quickly acquired a speed of 18 miles an hour, rose in the air, and flew a distance of fifty feet.
A remarkable deduction from the very careful measurements made with this machine was that it carried at the rate of 110 pounds per tow line horse power, when flying at an angle of 8 to 10 degrees. Mr. Tatin concluded: “These experiments seem to demonstrate that there is no impracticability in the construction of a large apparatus for aviation, and that perhaps even now such machines could be practically used in aërial navigation. Such practical experiments being necessarily very costly, I must to my great regret, forego their undertaking, and I shall be satisfied if my own labors shall induce others to take up such an enterprise.”
Tatin’s faith in the practicability of a large aëroplane was later voiced by Mr. Chanute in his valuable book, Progress in Flying Machines, published in 1894, but now unfortunately out of print. Recalling that Maxim had recently produced a large motor weighing complete only ten pounds per horse power, he says: “Aviation seems to be practicably possible, if only the stability can be secured, and an adequate method of alighting be devised.” Since the above quoted facts and opinions were published, no competent man well informed in the science of aviation has for one moment doubted the feasibility of human flight.
Fig. 34.—Hargrave’s Model Screw Monoplane, 1891.
In 1891, twelve years after Tatin’s experiment, Lawrence Hargrave, of Sydney, Australia, made a similar compressed air monoplane, with a single-screw propeller, but without wheels for launching and lighting. The model, which is shown in Fig. 34, had a wing-spread of 20 square feet, weighed about three pounds, and flew 128 feet in eight seconds. The weight carried was at the rate of 90 pounds per horse power, a very encouraging result. Two years later he described a small steam engine which he had developed, weighing 10.7 pounds per horse power, and capable of driving the model about two miles, though he did not use it for that purpose, being engrossed with other researches.
One interesting outcome of his numerous experiments was the Hargrave Kite, now more familiarly known as the box kite. A good example of his kites is the type shown in Fig. 35. This consists of two arched biplanes mounted tandem on a backbone, or connecting framework. The kite floats steadily, and was thought suitable for the body of a flying machine to be driven by an engine and propeller. Thus meteorology is indebted to aëronautics for its most useful kite.