The next apparatus to be noticed was thoroughly experimented with, and years were spent in the endeavor to put it into practical operation. It was first patented by M. Felix du Temple, a French naval officer, in 1857 and is shown in fig. 41; the top figure representing an end view from the rear and the lower figure being a top view. It consisted in two fixed wings of silk fabric, stretched by curved spars of wood or metal, and firmly attached to a car containing the motor. In front of this a screw was attached with a pivoted axle, in order to draw the apparatus forward. An horizontal tail hinged at the car was to regulate the angle of incidence and of flight of the machine, while a vertical rudder under the tail and separate from it was to steer to the right or left.
Fig. 41. -- DU TEMPLE-- 1857-1877.
The car was to be shaped like a boat, lightly constructed of wood or iron ribs, and might be covered on the outside with tarred or rubber cloth. Beneath it were to be hinged three hollow legs, which might either be folded up or allowed to hang down. Strong springs inside of them were to carry rods or feet, at the outer end of which were to be wheels to roll over the ground. These legs were to be so adjusted in length that the apparatus should present an angle of incidence of about 20 to the horizon, and upon being put into forward motion, at the rate of about 20 miles per hour, by the screw, it was expected to rise upon the air and to enter upon its flight, the latter being regulated by the horizontal tail and by the vertical rudder.
The motor might be steam, electricity, or some other prime mover, and it was estimated that 6 H.P. would be required for en apparatus; weighing one ton. This was a very great underestimate, for the proposed plan of driving the machine over the ground by means of the aerial screw would largely increase the resistance, and sufficient speed could not be obtained to rise upon the air.
M. Du Temple tried many experiments with models shaped like birds, and his patent indicates that he had carefully considered the question of stability, for he places the preponderance of weight toward the front of the car, provides for a diedral angle during flight by the flexibility and shape of the wings, and produces a slight turning up of the rear edge by making it flexible, all much as in the paper aeroplane which has been described. There was a weak point, however, in the fact that the center of gravity was not adjustable during flight so as to correspond with the change in the center of pressure, produced by such alterations in the angle of incidence as might result from the action of the tail or otherwise.
When he began with the aid of his brother, M. Louis du Temple, to experiment on a large scale, the inadequacy of all motors then known became apparent. They first tried steam at very high pressures, then a hot-air engine, and finally built and patented, in 1876 a very light steam boiler weighing from 39 to 44 Ibs. to the horse power, which appears to have been the prototype of some of the light boilers which have since been constructed. It consisted in a series of very thin tubes less than 1/8 in. in internal diameter, through which water circulated very rapidly, and was flashed into steam by the surrounding flame.
This is understood to have been applied to a slightly modified form of the main apparatus, built in 1874 at Brest by M. Du Temple. This was calculated to carry a man, was 40 ft. across from tip to tip, weighed about 160 Ibs., and cost upward of $6,000, the workmanship being very fine.
Careful search by the writer through various French and English publications has failed to discover any account of the operation of this machine, save the statement of M. Tissandier that "not withstanding most persevering efforts, no practical results could be obtained in experimenting with this apparatus."
In 1858 Jullien, a French clock repairer of Villejuif, who had already exhibited in 1850 the first model of a fish shaped navigable balloon which operated with its own motor, propeller, and steering gear, endeavored to prove what could be accomplished with aeroplanes. He exhibited to the French Society of Encouragement for Aviation a model weighing only 1 1/4 oz., although its aeroplane measured 39 m. across the line of motion. It was propelled by two screws each with two arms, and the power was furnished by the tension of a rubber band wound over two conical spools of equal diameter, like the fusée of a watch, in order to maintain the force uniform. The angle of incidence was about 10°, and the apparatus proceeded horizontally in a straight line a distance of 40 ft. in five seconds, with an expenditure of 0.52 foot pounds per second.
Jullien proposed to build a large apparatus upon the same principle, but he failed to obtain the requisite financial backing. He saw, clearly enough, that he must have a light motor, and he began to experiment with electricity, seeking chiefly a light primary battery. In 1866 he announced that he had succeeded in devising an electric motor and battery weighing at the rate of 82 lbs. per H. P. with which he expected to drive an aeroplane through the air during an entire day; but he did not receive the encouragement or aid of capital, and this ingenious inventor, who had struggled all his life long with inadequate means, died miserably poor, in a hospital in 1877.
The singular machine patented in 1860 by Mr. Smythies while quite impracticable in form, is here mentioned in order to make known two novel proposals-- i.e., the utilization of the aeroplanes as steam condensers and the proposed means for shifting the center of gravity while in flight. A top view is shown by fig. 42. The apparatus was to consist of extended plane surfaces in order to furnish the support, and to be propelled by the alternating motion of wings actuated by a boiler and engine of a peculiar kind.
The boiler was to be upright, its top view being indicated by the circles at the junction of the two planes. It was to be fitted with small vertical water tubes, thickly placed in a "flame-chamber'' heated by the combustion of some volatile fluid mixed with air. Back of the boiler an upright cylinder was to be placed to work the wings up and down, feathering motion being imparted to the vanes composing them (by compound levers), so that they should separate slightly on the up-stroke and firmly close on the overlap on the down- stroke.
Fig. 42. -- SMYTHIES-- 1860.
The whole of the two aeroplanes and of the upright boiler was to be encased in a closed flat bag of oiled silk or other light air-tight covering--that is to say, that a steam surface condenser was to be pro vided by making a hood, tapering,, on its top and bottom from the thin edges at the front and rear of the apparatus to a thickness at the center equal to the height of the boiler. This hood or case was to be kept distended by spars and by light cords, and the spent steam was to be exhausted therein so as to be condensed by contact with the sides, and the water thus produced was to drain into a reservoir at the bottom, whence it was to be pumped back into the boiler, thus keeping the total weight of the apparatus constant and utilizing the same water over and over again.
The operator was to be suspended in an adjustable seat beneath the center of gravity of the machine, and by shifting his position sideways or fore and aft, was to guide the machine to the right or left, or up and down through the changes thus produced in the position of the center of gravity and consequent angle of incidence. Elastic legs beneath the whole were to break the fall on alighting; the descent being, moreover, retarded by the action of the wings, in which both the amplitude of movement and the overlap of the vanes or "feathers" were under the control of the operator through a series of cords.
This apparatus as designed was quite impracticable, but it indicates that the inventor had been watching the birds and had become aware of some requirements overlooked by his predecessors, such as the necessity for adjusting during flight the center of gravity to coincide with the center of pressure consequent upon changes in the angle of incidence, in order that the equilibrium may be preserved; the necessity for more energetic efforts and greater angles of incidence at starting and in alighting than during horizontal flight, and also the necessity for an air condenser to liquefy the team, if the latter is to be used as a motive power, both to diminish the weight of the water required and to keep the weight constant.
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