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Aviation History
1910
1910 - 0140.PDF
|FyGHTJ FEBRUARY 26, 1910. THE NEW MAXIM AEROPLANE. By SIR HIRAM S. MAXIM. Six years ago I commenced making drawings with a view to building a flying machine with a petrol motor, but I did not finish it at that time, as I had a lot of other work on hand. AH the flying machines which have been built in recent years do not differ much from my original Baldwyn's Park machine, except as regards size and the kind of motive power employed. About eighteen months ago, in making a careful study of the whole subject, it appeared to me that the Baldwyn's Park type of machine, with slight modifications, was still the best that could be devised. I therefore decided to make another machine, on practi cally the same lines, but very much smaller, and to drive it with a petrol engine. I made the drawings, and about twelve months ago started to make a new light engine and a reliable carburettor, in fact, every thing relating to my present flying machine. The engine which I designed has four cylinders, each 5 ins. in diameter, with a common stroke of Sf ins. The cylinders, pistons-, connecting-rods, and the <rank-shaft, are made of a special brand of "Vickers" steel, which perhaps is the strongest and toughest steel that has ever been produced, in fact, I have never seen any thing to compare with it. It has a tensile strength of 57 tons, with an elongation of 14 per cent. This is remarkable, and it enabled me to make all the parts of extreme lightness and still have a reasonable factor of safety, moreover, the great lightness of the moving parts enables the engine to run faster if required than it would if the parts were heavy. In order to get a high speed if required, I made all the passage ways and valves of the engine very large and free. I had noticed at the various places on the Continent where I had seen flying machine engines in action that they worked very badly and un steadily, the exhaust being very irregular. A study of this question demonstrated only too clearly that the great trouble was with the carburettor ; the explosive charge was not thoroughly mixed, or per haps not mixed at all, and never of a uniform density. I therefore experimented on a carburettor and made one that would produce gas of a uniform density, and it was found that when the air and the gas were thoroughly mixed before they entered the cylinder at all, the petrol engine behaved exactly as a gas engine does. The exhaust was perfectly regular, and, as a well-known steam engineer said on witnessing the running of my engine, " It runs as steady as any steam engine I have ever seen, and altogether different from any other petrol engine." This engine has a forced water circulation^ and everything about the engine, including the spindles of the exhaust valves, is cooled, so there is never any overheating. A new system of oiling is also used. A small pump, having a bore of 1J in., and a stroke of 1^ in., is so arranged and driven by a train of gears and " clockwork," that the piston is raised against the resistance of a spring, and liberated four times in a minute, and the spring is of sufficient strength to produce a pressure of 120 lbs. per sq. in. on the oil, the result being that every part of the engine, . including the gudgeon-pins, is thoroughly lubricated four times a minute, and it has been found that no excess of oil gets past the piston into the explosion-chamber. The screw propellers are three in number. One is placed direcbly on the screw shaft, and runs, of course, the same speed as the engine, and takes the place of a fly-wheel; the others are very much larger, and revolve at a much slower rate. Two of the screws, the small one, and one of the large ones, rotate in a right-hand direction, and the other one in a left-hand direction, but the left-hand screw has a finer pitch than its mate, and revolves at a higher velocity, just high enough so that its gyroscopic action is equal to the gyroscopic action of the other two screws, and the rotating parts of the engine; therefore there is no gyroscopic action" at all when the screws are considered " ensemble" as the left-hand screw exactly neutralises the gyroscopic action of all the other rotating parts. The framework of the machine has been made of American yellow pine of a very fine quality. Although it is not quite so strong as spruce per square inch, it is really stronger than spruce when considered in terms of its own weight. Moreover, spruce was difficult to obtain. The machine has fore and aft rudders (balanced) and one horizontal rudder also balanced. The main part of the machine is made up of six aeroplanes ; the central section carries the machinery and the driver, and the two side sections are simply superposed wings, but they are not level. The outside ends are raised very much above the central section, and their surfaces are curved in such a manner that when the machine is in the air whichever side is the lower will lift the most, This ensures lateral stability, without the necessity of any machinery. I know that some mathematicians might dispute this, as they be lieve, or think they believe, that the pressure on the aeroplane is always perpendicular to its surface, but if they would give the matter one moment's careful consideration they would know that such is not the case. It would be a case, I will admit, if the whole machine was mounted on a shaft, and could rotate in the air after the manner of a windmill, but the machine is not mounted on a shaft, it is sus pended in the air and resting on the air, and falling through the air at the rate of 6 or 7 miles an hour. True, it is going ahead at the same time, but nevertheless it is falling as relates to the air, therefore its downward motion through the air, while travelling, has the same effect as it would if the machine was not travelling at all, but simply falling through the air. Therefore, the side that is lowest and presents the best angle to the wind, and also presents a lifting effect farthest from the centre of gravity, must lift the most, and have a strong tendency to keep the machine on an even keel. The centre of gravity, however, is very low, and very much below the centre of lifting effect. This, of course, also tends to keep the machine right side up. I have also applied a device which I invented and patented many years ago, which enables the pilot to vary the pitch of the wings while the machine is still in flight; but instead of doing it after the manner of the Wright Brothers, I strictly adhere to my original patent, the wings being moved in one direction by hand, and in the reverse direction by a spring. But this device I do not think will be absolutely necessary on account of the shape of the wings and the arrangement of the weights. In making this machine I have sought to group all the parts together, as near as I can, in line (tandem) in order to reduce the atmospheric resistance as much as possible, and to have what there is of it in the path of the screw, that is, the motor, the driver, the densest part of the framework, the magneto, steering-gear, and the petrol tank are all placed in line very low down, and all in the path of the small screw, so that if it should take, we will say, 10-h.p. to overcome the resistance of these parts, the 10-h.p., having been expended on the air itself, would draw the air forward in the direc tion of flight, so that the screw would be running in air which was already advancing, and fully 80 per cent, of the energy would be recovered by the screw. It is the same also with the two large screws. All the parts that offer considerable resistance are forward of the screw, so that as much as possible of the energy lost in atmospheric resistance will be recovered. The width of the aeroplanes fore and aft is 6 ft. 6 ins., and they are 6 ft. 6 ins. apart. I have not given so much curvature to the aeroplanes as one would find on most of the machines of the present day, because in my early experiments I found that, when we consider the lifting effect of an aeroplane in terms of the drift, the thin aeroplanes, which are only slightly curved, do the best. Quite true, they do not lift so much per square foot, but they lift more per h.p., and I have preserved the shape which was found best at Baldwyn's Park. Both the top and the bottom sides of the aeroplanes are covered with very thin and extremely strong waterproof silk. It is altogether the strongest and lightest I have ever seen, weighing only about 2 ozs. to the square yard. This silk is laced on to the aeroplanes with a great deal of care, and the whole of it as tight as a drumhead. The aeroplanes are thin and sharp. The stays are of two kinds— oval steel and fiat steel, and the struts partly of oval steel tubing and partly ol American pine. The total width of the machine is 44 ft. One of the novel features of the machine which makes it look so much neater and simpler than other forms is the manner ot constructing the frame and mounting the screws. Instead of having a lattice-work frame running round the screws to support the aft rudders, the screws are not mounted on a rotating shaft, but rotate themselves on a part of the framework of the machine. In fact the real foundation of the machine consists of two steel tubes, to which everything else is suspended or attached, and it is these steel tubes on which the screw-propellers rotate. This enables the principal member of the framework of the machine to pass directly through the centre of the screws, as an extension of these steel tubes carries all the rudders—fore, aft and vertical. The screws being of very large size—over 11 ft. in diameter—of necessity have to be made very thin, in order to be light, and also I36
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