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Aviation History
1910
1910 - 0753.PDF
SEPTEMBER 17, 191s. increase directly as the length, and the total power also increases directly as the length, and therefore as the weight. It would be expected that the power obtainable should vary as the weight of rubber, however it was arranged, and whether the varia tions were in thickness or in length. We now have the two facts established, viz., that the torque increases and decreases with the cross section only, and the number r,«i. JH* '^^VTOTCTr^rrrTTCv.v.>^ttt>t>t.t»W\VW\\\^>VU^^^i «iwiiu<ii!tf:iit,mitfim *L F.g- 2. Pie-5. of revolutions can be taken to vary only with the length, for cross sections above 16 strands, and, as shown in curve I, for lesser numbers of strands. As a working figure, it may be taken that any number of strands above 16 will give 120 revolutions multiplied by the length in feet up to', say 50 strands. It is hardly likely, for other reasons, that greater thickness would be used, but if it should be, take 100 multiplied by length for the revolutions. The use of these figures will be best understood by taking a few examples. ffUCHf Figs. 1 and 2 represent two motors as used in practice, and which therefore need not be described in detail. Each is supposed to consist of 16 strands of -fa-m. sq. elastic; in Fig. 1, 2 ft. long, in Fig. 2, two lots of 1 ft. long. Thus there is the same weight of elastic in each. The curves show that in Fig. 1 the torque is 277 ozs., and with the help of Table II the revolutions will be 286 ; therefore the total work = 782. This may be called a high-speed motor. In Fig. 2 each rope of 16 strands gives a torque of 277 ozs. As the ropes are fixed to the same revolving part, viz., the centre gear wheel, the total torque is doubled = 5'54 : but as the length of each rope is now half, the revolutions = 143, but the total work obtainable is the same = 782. Since the weight of the elastic is the same, this may be called, with respect to Fig. I, a slow-speed motor of the same power. If the same screw is used, it should therefore be geared up as shown to obtain the same speed. The advantage, if any, of Fig. 2 over Fig. 1 lies in the end pull of the elastic being taken at fixed ends ; the thrust of the screw remains, and the friction of the gear is added ; the advantage then lies between the loss by the end pull on a suitable bearing to the loss by gearing. Of course, if a slow-speed screw that is equally efficient can be used, so much the better. Fig. 3 shows another way in which the sixteen 2-ft. strands might be grouped, viz., in eight ropes of two strands each ; all the ends at one end are geared together, and one of the gear-wheels is fitted with the screw. All the other ends are fixed, the screw is wound up in the usual manner, winding the remaining ropes, by means of the gears. The torque will be i"04 ozs. (that is, -13 x 8), the revs. = 804, and the total work = 835, the same practically as before ; this gives a high-speed motor as compared with Fig. 1, though owing to the loss by friction of the gears it may not be an improvement, but these examples serve to show how a number of groupings can be arranged to vary the torque or revolutions, to suit the screw without altering the length or weight. Want of space prevents me from giving the torque to twist curves from which the above figures have been obtained, but, as I have briefly described, the torque is very irregular during the period of working ; it therefore seems to me that the screw most suitable for this kind of motor should have as high a moment of inertia as possible, even with an increase of weight such as lead blade-tips, so that it may store up and therefore smooth out these inequalities. To grind down to waste the peaks of the torque curve, by not using a ball-thrust, and thereby making the screw run steadily, is not a good plan, though I have known it to be suggested. BRITISH ASSOCIATION AERONAUTICS. As might be expected, the science of mechanical flight came in for some consideration at the British Association meeting at Sheffield last week. Fortunately, moreover, its interests were advanced in consequence, although in a totally unanticipated and in a somewhat unorthodox manner. The treatment of the subject had been entrusted to Professor G. H. Bryan, who opened a discussion on the principles of mechanical flight before a joint meeting of the engineering, the mathematical, and the physical sections. As events turned out, Professor Bryan proved to belong to that school of thought which deprecates the ability and utility of the practical man in comparison with that of the mathematician and the scientist, at any rate during the initial stages of any such new development as aviation ; and he went so far as to speak of the epoch-making flights of the present day as being evidences of foolhardkiess rather than of bravery, because he was pleased to imagine that a lack of equilibrium and stability rendered impracticable the present-day experimental machines, and that only one or two exceptionally 250,000 Francs for a Race and a Counter Proposition. A VERY sporting proposition has been put forward by Mons. Quentin Bauchart, a member of the Municipal Council of Paris, that a big circuit race round France shall be organised next year for aviators; to include as main points Paris, Bordeaux, Toulouse, Marseilles, Lyons and Dijon, a total of about 1,000 miles—in fact, a contest very similar to the Daily Mail all round England race for ;£ 10,000, in July next. M. Bauchart is urging the Paris Council to vote for this project a sum of ^8,000 to be awarded as prizes, this being, he contends, the finest means of helping forward rapidly the advance of aviation in a similar manner to the big circuit prizes which were given in connection with motorism in its early days. 751 capable mathematicians were capable of making substantial progress at the immediate moment. Ultimate, and as we trust permanent, good resulted from this peculiarly biassed and misleading onslaught, since it brought forth the most vigorous protest from many prominent men, and thereby helped to lay by the heels an all too popular misconception of the present position of the new science. Sir William White, in particular, made scathing reference to the disappointing nature of those " beautiful mathematical formulas " which generally have a coefficient to make them work ; and he pointed out emphatically that if it had not been for the practical airmen of the past year or two, who had gone up into the air and taken the risk, that we should not be where we are (now in the development of the aeroplane. Mr. Dugald Clerk and Mr. Worby Beaumont, amongst others, assisted materially in neutralising the mischievous effect of the views aired by Professor Bryan. ® 9 Byway of a counter suggestion to this, the L.N. A, have suggested a mere circuit for this prize would not do so much good in benefiting the growing industry as if the money were allocated as prizes to a competition for motors and propellers, as by the perfecting of these two indispensable parts of the aeiroplane, efficiency will be obtained more rapidly, which will do more to help forward the whole industry than any tour could possibly do. Beth sides have very good arguments on their side, and we should like to see not only in France, but in England, two similar projects carried out as it were complimentary to each other. Already we have the magnificent ^10,000 prize of the Daily Mai! for the all-round England race. It is only the big prize wanted now for the encouragement of the motor and the propeller. D 2
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