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Aviation History
1917
1917 - 0120.PDF
FE»RUART I, 1917, SOME PROBLEMS IN AEROPLANE CONSTRUCTION. By CAPT. V. E. CLARK, CAPT. T. F. DODD, and O. E. STRAHLMANN. (Continued from page 97.) Melal construction for aeroplanes.—It is suggested that thefield for development of steel or aluminium alloy in the structure of aeroplanes is one offering considerable induce-ment. The authors have gone briefly through the layout of an aeroplane in which every strength member is of metal.In this design it was found most convenient to use seamless steel tube at some places, welded tube at others, channelsection at others, I-section and L-section at. others. At a few points aluminium alloy was used, at other points purealuminium, assumption being made that this aluminium was rolled in such a way as to give it certain desired physicalcharacteristics. It is suggested that, even with the present standard method of construction, there is great room forimprovement in the material and method of heat treatment of the metal fittings used in conjunction with wood andwire. Especially where fittings are bent both with and across the grain, a special alloy appears advisable. The sameholds for fittings shaped by die forging. Chrome vanadium steel, to comply with S.A.E. specifications 6130, and heattreated in such a way as to render it best in each case, is uggested. It is believed that the total weight of an aero-plane can be materially decreased, without sacrifice of strength, and hence superior performance obtained, by theuse of better steel. The construction of floats of metal for seaplanes appears to be a possibility as is also the use ofmetal for aeroplane propellers. It is possible that the entirfe body might be made of light pressed steel, or aluminium,with holes to decrease the weight cut at proper places, and covered with linen. e "Flexible piping.—Satisfactory flexible gasoline lead hasnot yet been developed. Such a lead should resist the action of vibration, should be light in weight and resist cutting ordenting. The method of making joints is important. The duct should be carefully sweated into proper terminal fittings.Tube ends of fittings should have spiral springs wound around them for at least 2$ ins., thus preventing sharp bends anddistributing the effects of vibration. All unions should be ground, which spherical seats, and threads should be cutclear and sharp, with all burrs removed. The inside diameter of tube should not be less than 0-35 in. A flexible pipe,light in weight, of material suitable for leading the exhaust away from the engine would be useful. Muffler requirements.—In military service a hostile aero-plane is usually first discovered by hearing it. A muffler satisfactory as to low weight, flexibility, loss of power throughback pressure, durability against corrosion and efficiency as a muffler is highly desirable. Shock absorbers for landing gear.—Rubber is not satis-factory as a shock absorber for heavy aeroplanes. Neither is it satisfactory as a military supply, especially when it issubjected to heat and the direct rays of the sun. It seems necessary to develop a steel-spring shock absorber. Theaction of this steel spring must, however, be damped by an oil cylinder. Without this damping the action is suchas to cause the aeroplane to bound excessively upon striking the ground. Brakes required when landing.—The development of abrake to reduce the run of the aeroplane after it has touched the ground, thus permitting it to land in restricted areas,appears to be a difficult problem. It is a moot question whether such a brake is desirable when the simple two-wheel landing gear is used, as its action has a tendency to throw the aeroplane over on its nose. Where more than twowheels are used, however, a brake fitted to the two main . rear outside wheels in such a way that the pilot can, fromhis seat, operate either brake, or both brakes together, would be desirable. Such an arrangement would permit him notonly to stop his machine quickly, but also to steer it on the ground to some extent. Folding landing gear.—The development of a landing gearthat can be submerged within the body by the pilot, during flight, would materially increase the speed of the aeroplaneby reducing the " parasite " resistance. Such a mechanism should be light in weight, sturdy and simple. Gasoline-supply gauge.—The development of a gauge toindicate the supply of gasoline remaining in the tanks to the pilot, whose seat can tte out of view of the tanks, isnecessary. Such a gauge should be simple and sturdy. The accuracy and reliability with which it registers shouldnot be affected by any change in altitude of the aeroplane. It should not form a possible source of leakage. It shouldbe adapted to both the pressure and suction systems of feed. Fire safely device.—Many casualties have occurred because the aeroplanes have caught fire in the air. While it has beenimpossible to determine from the wreck just what led to the fire, it is quite probable that many of these accidents weredue to back fire into the carburettor that forced burning gasoline out into the surrounding structure, or to a leakinggasoline tank. The development of a device that will render such an accident impossible would save many lives. Inthis connection it should always be a rule for aeroplane constructors never to have any electric lead near a gasolinesupply or lead. A Ititude adjustment for carburettor.—The development of adevice to regulate automatically the mixture for variations in density of air incident to changes in altitude would bevaluable. Device for firing machine gun by engine shaft.—A systemby which machine guns would be fired by positive action of one of the engine shafts is necessary on a single-tractorscrew machine on which it is proposed to fire through the disk of the propeller. The most convenient way wouldprobably be to fire from a camshaft, as it is believed that fire at the rate of 600 per minute is the reasonable limit"The firing pin on the gun should strike the primer at the instant that the rear edge, of the blade passes the line of fireof the gun. The propeller should be two bladed for this work. Such a device should be simple, durable and reliable. Vibration-absorbing material.—The development of amaterial more suitable than ordinary felt for padding the points of support of radiators, and the like, is highly desirable. Variable radiators.—A more suitable method of permittingthe pilot to adjust the amount of cooling done by the radiator in order to compensate for changes in temperature of air,or changes in speed through the air, is necessary. Such arrangement should permit operation by the pilot from hisseat during flight, or, better yet, might be automatic ; the 3.—Variable forms of aerofoil sections. device being operated as a function of the temperature ofthe water. It should be durable and should act with reliability. Variable-camber wing.—Great speed range is a desirableattribute of an aeroplane, as it permits high speed of travel in the air and yet low speed while landing, which, of course,makes for safety if the landing place be small or rough. Great improvement in the speed range can be brought aboutby use of a variable-camber wing surface, that is to say, if T ~ ~«o 90 100 . 110 SPCED.MILES PER HOUR Fig. 4.—Performance curves for aeroplane with fixed-camber wing. 120
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