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Aviation History
1910
1910 - 0854.PDF
that of the gas vessel. Surely a far better plan would be to place one large propeller at the stern of the gasholder and another smaller one behind the car. I enclose a sketch ot the arrangement I suggest. I notice in the September 3rd issue of FLIGHT a paragraph describing an arrangement of mirrors fitted to an aeroplane so as to enable bombs to be accurately dropped on to warships. It may interest some of your readers if I ^^^ recall that the same idea ^^~\^ A occurred to my father, Mr. /^if George Griffith, who intro- jL^O duced it in his novel, " The ~^/ /f Angel of the Revolution." •t^cl rs-gH<* This book was published seventeen years ago. The appliance was supposed to be fitted to the French and Russian war balloons, which destroyed the remnants of the British Fleet by its aid. The war balloon was manoeuvred above the ship selected till the glare of the funnels was seen reflected in the mirrors ; a bomb of dynamite was then dropped by opening a trap. Douglas. A. A. GRIFFITH. STABILITY OF THE VOISIN BIPLANE. [816] Apropos of the all-absorbing question of lateral stability, can you inform me why Voisin has discarded his vertical curtain type of machine ? I have always considered that the solution of this stability difficulty would be found in correctness of design of an aeroplane, and the "box kite" idea of the Voisin machine as originally built appeared to me to be a long step in the right direction. Regarding the efforts of your correspondents to secure stability by means of pendulums and the like, I would recommend that they look through the Patent Specifications at the nearest library where they are kept. The patent specifications which will interest them will be found in the "Subject Matter Index" for each year under the heading "Aeronautics," sub-heading "Steering, balancing, and regulating altitude, automatically." I should think that every possible application of a pendulum to secure stability has been patented at one time or another, but I have never yet heard of a machine fitted with a pendulum making any kind of a flight. The idea appears to me to be bad in principle. There is the dis advantage of oscillation, the disturbing effect of air-pressure at flying speed (which is bound to be considerable), and, where the pendulum is used to directly actuate, by its weight, the lifting aileron, it will be found that the moving of the pendulum towards the end of the plane which has dipped below the horizontal will always balance the lift which it gives to such aileron, consequent upon the moving of the centre of gravity towards the end which has dipped. Pendulums opening valves for the operation of ailerons by com pressed air appear to be the least objectionable, but the patent records are full of them, and I think the failure of these may be attributed to the fact that they are unable to adapt themselves to any particular circumstances. It is not always advisable, one would think, to actuate the lifting aileron for a dip of, say, about 50 from the horizontal, but the pendulum, assuming that it is in good working order, would open the valve immediately, and the resulting lift would throw the end of the plane which had been depressed as far above the horizontal as it had previously been below it. The result of the machine thus oscillating, with the pendulum-valve doing a little oscillation " on its own,' may be imagined. Apologising for the length of this letter, and trusting you will be able to give a reply to the first part rt the Voisin machine (I will depend on pendulum inventors for a reply to the rest !). Manchester. "SIMON." [The original Voisin biplane, although undoubtedly possessed of a fair degree o( natural stability of a kind that made it a suitable machine to learn on in fine weather, is nevertheless seriously handi capped in point of speed and in the facility of quick control necessary to the winning of competitive events, which in themselves constitute a governing factor in the development of aviation at the present time.—Eu.J EARLY HELICOPTER. [817] Maybe W. A. Harvey (639) and others of your correspon dents who have made inquiries >r helicopters, are seeking information of Wollaston's brolly-screw (helicopter parachute) soaring apparatus, invented and made by the brothers Herbert and Ernest, experi menting at Miller's Flat, Elmstead, Kent, 1885-88. This machine was a soarer only, not a flyer, being always held captive. It was never started from ground, but from a bent iron rod at the end of a 22 ft. long ash pole. This pole was balanced near the half length on a forked pivot, so that it could be swung clear after release of brolly. The pole itself was on a tripod 12 ft. in height, starting as follows : From one end of pole to the other, through guides, ran a cord to a snatch-link on bent iron at end of pole. The snatch- link closed by spring into ring attached to screw-spindle cap on top of brolly. About 15 ft. of strong rope was fastened to other end of pole, some length of snatch link cord hanging free. The weight of brolly just brings pole down, the Wollastons standing at rope ready to pull as soon as "pilot" has seated and strapped himself secure. The " pilot" was in every trial, myself, weighing then 7 stone 6 to 9 lbs. At signal " All right," a see-saw steadily up and down by pulling and giving on rope until the screw has attained its greatest momentum, then when the brolly end of pole is at its greatest height the snatch-link cord is pulled, the pole being swung clear instantly. After release the brolly slowly descends a few feet, but "pilot" working quickly the brolly soon gathered purchase and rises. The tether-ropes are attached to foot-rest by swivel. After having reached height thought advisable to ascend, two grip-catches are let go by " pilot," which engage with tether-ropes, those holding such go wider out, and so stop spinning motion ; 60 to 80 ft. was about the usual, although of course very much higher could have been attained. Over 100 ascents were made, and on June 16th, 1887, Mr. Shadbolt, balloonist, was a very interested assistant with brolly and gliders, tripod and pole. Fitments were made by Dean, ladder-maker, Redhill. To any of your readers who are bona fide experimentists with helicopters I will gladly give fuller details if inquiries sent under cover to FLIGHT. Orpington. PIONEER. AEROPLANES AND YACHTS. [818] I have for the past three years been contending that an aeroplane should—to be stable—have a greater chord than span, so I read with great interest your article on " Flyers and Yachts." I am rather amused to find that you are using, in recommending the broadside aspect, exactly the same arguments as I have been using for the end-on aeroplane. We are, therefore, not likely to quarrel over facts. With respect to the Tee test, you say, " If the paper has been cut as it should, the piece falls like a stone, without swerving one way or the other." Exactly. And if allowed to drop broadside on " quite a different result will be observed, for the T will reverse in its descent so that it reaches the ground stem first, as in the former case." If this proves anything, it proves that end first is the easiest and most stable way through the air, and that broadside first is so unstable a method of progression that if the slightest draught cause it to swerve from its course by a hair's breadth it at once turns turtle and resumes its natural and proper position. Then you say " the T piece of paper, as we have seen, reverses i. dropped head (broadside) down, but except for this one manoeuvre, it may otherwise be described as stable in its path of descent." I am here forcibly reminded of the famous description of a crab as a "little red fish that walks backwards," and the criticism that although the crab was not necessarily little, was not red, was not a fish, and did not walk backwards, yet except for these slight errors the description was quite correct. Could we not say, Mr. Editor, with equal justice that a pyramid standing on its apex might turn over on to its base, but except that for this one manoeuvre it was quite stable? I agree with you that there is " only one stable position, and that position is attained automatically." It is : End on. Your arrowlesson, again, goes directly against your broadside on principle, as, in fact, does everything in nature with one exception —the bird. Now you will say that as the bird is the only thing that moves in the same medium as the aeroplane, the fact that he goes broadside on is sufficient to prove your theory. Mr. Editor, I think the greater part of all the difficulties that retard the progress of aviation is the absurd idea that an aeroplane must be shaped like a bird. There is not the slightest likeness between the two things. A bird uses its wings as levers to lift and propel itself. Does an aeroplane have wings for that purpose ? Well, why copy the shape ? But an aeroplane glides, and a bird glides, both broadside on. True, and the glide of the bird is so unstable that its wing and tail tips are incessantly at work to preserve its equilibrium, and even then, though the countless generations of practice have made the movements automatic, it often loses its balance in a gust, and has to flap and control itself to recover. As to the glide of the aeroplane, let the death-roll of our aviators tell how stable it is. When our aviators have developed a bird's brain, a bird's sense of balance, a bird's nerves, muscles, and strength, and a bird's capability of nice adjustment of wing tip to air pressure, we may shape our aeroplane like a bird, and the aviator may, perhaps, succeed in keeping it balanced and avoiding that « one manoeuvre " by which the force of gravity seeks to assert itself. For my part I prefer to have the force of gravity as much on my side as possible. )2
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