AERIAL CARRIAGES. T HE name "flying-machine," though a taking title for
a British Association paper, hardly does justice to the serious side of the ingenious experiments on which Mr. Maxim has lately spent much thought, time, and money in order to clear the way towards a practical solution of some of the diffi- culties of aerial locomotion. The term itself almost suggests the impossible, and it is not a true description either of Mr.
Maxim's machine or of any of the main principles used in practical aeronautics. " Flying," or propulsion by the beating wing, is far too complicated and delicate a movement, or rather series of different movements, and demands mechanical adaptation too specialised and too dependent on voluntary adjustment by the user, to make it a practical basis for aeronautic experiments, though the several movements of the beating wing are now analysed and stereotyped by means of the instantaneous photograph. No mechanical contrivance of webbing or membranes has yet added to the powers of swimmers in water, though the movements are far more simple than in flight.
The suggestion of something visionary and unpractical in the term " flying-machinie " is inevitable ; and as Mr. Maxim's reputation as a practical inventor of extraordinary ability is being daily confirmed by the growing reputation of his auto- matic cannon, perhaps the "neatest" mechanical invention of the day, we hasten to say that his " flying " machine is not intended to "fly" at all, but depends for its aerial power on a totally different principle. "Soaring," not "flying," is the object for which it is intended. Any one who has grasped a large kite, held at an angle, in the centre near the crossing of the lathes which make the frame, and then run forward against the wind, has felt the lifting power of the kite, and its efforts to rise. Held in such a way, and at such an angle, the kite becomes, in scientific language, an " aeroplane," and it is a " sky-scraping " contrivance of this kind which forms the working principle of Mr. Maxim's machine, elaborated with all the mastery of design, material, and propelling power which the inventor's knowledge commands. Without setting an undue value on the results of his experiments, we may men- tion one or two points in which Mr. Maxim's methods have the advantage, both from the scientific and common-sense point of view, over the forms of aerial carriage which are from time to time invented by persons less conversant with the proportions which must be observed between the different means used. It is clear that, in the case of the " kite- aeroplane " mentioned above, the lifting tendency of the kite is due to the running powers of the man. If only the kite were big enough, and the man could run fast enough, there would come a moment when the kite would lift the man, and if running could then be changed into some other form of propulsion, he would soar upwards. Clearly the pro- pelling power is the main problem, if the "aeroplane" method of ascent is to be used,—a factor which most inventors of " flying-maohines " are apt to forget, and leave what is the first condition of success to the suggestions of a " consulting engineer." Mr. Maxim has faced this difficulty first, and overcome it. He drives his aerial car by screw- propellers, 18 ft. across from the tip of one blade to the tip of the other, the propellers working in air, just as those of a steamer work in water. Above the propellers is the great aeroplane, and smaller aeroplanes project on each side, the extreme width being 125 ft., and the length 104 ft. The lower deck of the ear on which the drivers stand, is not wider than a railway carriage ; but the weight of the whole machine is 8,000 lbs., or roughly speaking, four tons. Driven at the rate of 60 miles an hour, with the aeroplanes set at a slant of about 71 degrees to the horizontal, Mr. Maxim's machine has a lifting power of 10,000 lbs., or 2,000 lbs. more than its weight, with engines, boilers, water, and fuel aboard, —a wonderful instance of the advance in efficiency made by modern steam-power. The boiler is made of copper tubes hardly larger than a pencil, and is heated by jets of " gasoline," an oil which has the curious property of burning like a gas- flame as it emerges in the liquid state from a tube. The power developed by the engines in proportion to the weight is indeed surprising. The actual horse-power delivered to the screws is 363, of which 150 goes to lift the aeroplanes, 80 to drive the machine, and 153 'are wasted in the mechanical imperfections inseparable from the use of "screws." If the Maxim car were a real " flying-machine " capable of giving rhythmical beats of the wing, with the extraordinary range of rise and fall in the movement of the wings, from one position in which they are raised almost vertically above the back, to another in which the tips almost meet below the breast, which M. Marey's "photographic gun" has detected in the flight of birds, there would be no limits set to its aerial range by want of " power." But to have the power and to be able to use it are different things. It was pointed out in an ingenious paper read two years ago at the British Association Meeting, that in the case of certain torpedo-boats the propor- tion of power to weight equalled that used by some birds in flight, and in the case of one vessel it was the same as is required for the flight of the duck, in the proportion of about 18 horse-power to the ton.
But as the car is lifted by immoveable aeroplanes forced against the atmosphere by steam, it is not in the flight of birds that its analogies must be sought, and the defect of our powers of mechanical contrivance in one direction have to be made up by an excess of force in another. The Maxim car shows a very modern use of modern knowledge, especially in its frank acceptance of the limits which we must submit to in devising means of aerial locomotion. In the one instance in which a factor of bird-flight is adopted, it is modified with singular ingenuity. Starting from level ground is almost as great a difficulty to large heavy birds as in the case of " flying-machines." They nearly always require a long run "to get up steam" before rising into the air. An eagle, surprised on a sandy plain, was seen to do this, running and beating its wings, and the tracks on the sand measured forty yards. Condors are commonly taken by leaving a bait of carrion in an inclosure, which pre- vents the "run,' and consequently the power of rising. Mr. Maxim provides his oar with the power for a long initial run, by the simple plan of setting it on rails ; and in an experiment at which Lord Kelvin and some brother inventors were pre- sent, the car attained a speed of sixty miles an hour ; and after running nine hundred feet, rose from the rails and travelled in air, held down by two other rails, which were set a few feet above those on which it travelled, to control it when in the air. Unfortunately it broke loose from these, and steam had to be shut off, and the experiment stopped, but not before the machine had shown that it could rise and travel in the air. It is more difficult to gather Mr. Maxim's own views as to the value of his invention than those of others. Sir Robert Rawlinson cites the sad case of a Belgian who some years ago made a " flying-machine," which he lifted into the air by means of a balloon, and then, detaching him- self and his machine from the balloon, fell to the ground, and was killed ; and other experiments, in which the experimenter generally mounts, some high building, falls to the ground, and breaks a limb or his neck. Sir Robert Rawlinson might as well go bank to quote the case of Icarus ; for, apart from the fact that there is in Berlin a certain Mr. Lilienthal, who has for many months amused himself and delighted his visitors by sailing off a tower with aeroplanes fixed to his back and arms, and so emulating the performance of the flying- squirrel, the Maxim machine is designed to soar from the ground proprio molu, and not to be dropped like a parachute. The compliments paid to the inventor by Lord Rayleigh and Lord Kelvin do not include anypronouncem ent on the practical value of the experiment, though Professor Langley _surmises that during the next ten years "flying-machines" will take a place among existing practical inventions. That is partly the case already. Fifty-two balloons were sent out of Paris during the Siege, after October 7th, 1870, when Gambetta rose from the hill of Montmartre, in charge of the great aeronaut Nader, to organise the Army of the Loire from Tours. Each balloon carried a budget of news from the city to the provinces, and one or two baskets of carrier-pigeons as return messengers ; and it is worth noting that the balloons, and the birds so conveyed, were the sole means of communication with the outside world during the siege. Neither men nor dogs could pierce the German lines, and the cable in the bed of the Seine was cut, its place betrayed by a Frenchman. The use of aerial locomotion in the Siege of Paris is itself an encouragement to further experiment, and though the French Government abandonel its research in that direction after the capitulation, it may be hoped that the success which Mr. Maxim has already won may encourage him to further experiments.
Previous page
