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Aviation History
1909
1909 - 0013.PDF
JANUARY 2, 1909. structed for M. Archdeacon some cellular kites of a large size, of very much the form of their present type of machine ; these were tested in tow of a motor launch on the Seine, and provided much of the data that MM. Voisin afterwards utilised in the construction of the actual flying machines that brought their work into public prominence. MM. Voisin -and their engineer or works manager M. Colliex, who is largely responsible for their designs) make no secret of the fact that they have based their work on that of pioneers such as Lilienthal, Langley, and others, and in fact they say that they never miss an opportunity of utilising any information or data on which they can lay hands. On the other hand, much of their work is based on their own researches ; they appear to take little for granted, having equipped themselves with an "artificial wind" apparatus, with which they test itheir work on a small scale before finally settling a design. J The Voisin factory is on a comparatively small scale ; the output and work in hand at date includes (amongst others) some five machines of the Farman-Delagrange type, and four machines of a modified Photo by J. 'Iheodor^w, . Side view of the Voisin-Delagrange biplane. pattern, with an aerofoil consisting of three superposed members. The former is the only type of machine for which flight data are to hand, and in the remarks that follow it is this type to which reference is made as the Voisin machine.% It appears from statements made to the author by MM. Voisin and confirmed by Mr. Farman himself) that when their designs were prepared, the first order they obtained was from M. Dela- grange and the second from Mr. Farman, who placed his order for what was practically a duplicate machine. That Farman made successful flights before Delagrange was due in the main to the fact that he had made in advance appropriate arrangements for testing and trials on the Champ de Manceavres at Issy-les-Moulineaux, a pre- caution that the latter neglected, and it would seem that it is hope- less to attempt to fly, at least with a new machine, without some such provision. It also appears that the Delagrange machine went through some kind of a history in its early state, the wheels fitted in the first instance not being arranged as it was subsequently found • necessary to arrange them, namely, as castors, or as the French express it, " orientable." It is this provision that takes care of any . slight side component of the wind when starting and alighting which i might otherwise upset the machine. s The Voisin machine is given as weighing complete, with Mr. Far- man "up," 1,540 lbs. (700 kilogs.), and has a total supporting surface of 535 sq. ft., this being the combined area of the horizontal members of the aerofoil and the tail, both being used for sustenta- l_ tion, though there are reasons for supposing that the pressure per I sq. ft. on the aerofoil is greater than on that of the tail. t It is of interest to note that MM. Voisin and their staff are entirely-responsible for the design of their machines, and guarantee that they mill fly. The purchaser pays for his machine in part as a deposit, and the remainder•when the machine has actually flmvn. It is time that the false impression that has been conveyed to the public by the Press should be dispelled. Messrs.Delagrange and Farman (Voisin's first customers) had no more to do with the design of their machines than the purchaser of a motor car from the manu-facturer. § So far as the author is informed, the " triplane " type of Voisin machine(Goupy 1), has not performed so well as the earlier model (Farman type) though this may be due to the short time that it has been in the hands of the aeronauts.The author believes that the three members of the aerofoil are relatively too close to one another for hest efficiency ; their aspect ratio also is not good.Beyond this the position of the propeller (in front) is one not conducive to the best efficiency, and the race of the propeller in such a position may materiallyadd to the body resistance. The ordinary maximum velocity of flight is approximately 45 miles per hour, or 66 ft. per sec. ('=72 kiloms. per hour). In addition to the horizontal sustaining members of the aerofoil and tail there are a number of venical members whose function is to preserve and control the direction of flight, and to give lateral stability ; these have a total area of approximately 255 sq. ft. The supporting surfaces of both aerofoil and tail are of rectangular plan form, the former being 10 metres by 2 metres, and, therefore, having an aspect ratio — 5. The aspect ratio of the tail members is 1 '25 ; they are, therefore, nearly square. The Voisin machine is propelled by a single screw of 7 ft. 6 in. diameter (2-3 metres), of which the effective pitch is approximately 3 ft. (the actual pitch is much greater, the " slip " being excessive). The propeller is keyed direct to the motor shaft. The motor fitted to the Voisin (Farman) machine is an 8-cyl. " Antoinette," 4-35 ins. diameter by 4-15 ins. stroke (no mm. by 105 mm.), stated to give 49 b.h.p. at 1,100 revs, permin. ; its weight is given as 265 lbs. (120 kilos.). It is said that the gliding angle of the Voisin machine was at first approximately 1 : 5 or 11 degrees, but that by detail improvements in diminishing framework resistance by rounding off and covering iu to form stream-line sections, the gliding angle has been improved, and is now about "16 radian, that is between 1 : 6 and 1 : 7, or 9 degs. approximately. Comparison of the Two Machines. Weight.—The first point to which we may direct our inquiry is that of the difference of weight: the Voisin machine is 40 per cent, heavier than that o* the Brothers Wright. Since the passenger accommodation of the two machines is almost identical (both machines have shown themselves capable of raising one person of ordinary size in addition to the aeronaut), it might be supposed that the less weight of the Wright machine is a definite advantage ; in fact, it might be thought that the less weight betokens more scientific design ; claims in this direction have, in fact, from time to time been made. There is, however, one feature in which the machines differ, and which is unquestionably responsible for much of the difference in weight. The Voisin machine is fitted with a " chassis " with four wheels mounted to swivel freely, this being an essential feature of a well designed alighting mechanism ; the front wheels are provided with a spring " suspension " to diminish the shock of landing or consequent on starting or alighting on rough ground. The Wright machine has no such provision, but possesses instead a pair of wooden runners of comparatively little weight. The total weight of this " chassis" of the Voisin machine is said to exceed one hundredweight (50 kilogs.), and even if this is an exaggeration it certainly cannot be far short of that amount, and Photo by /. Theodorescfl, Paris. : The Voisin -Delagrange biplane in full flight. probably^texceeds the corresponding weight carried by the Wright machine by at least 60 or 70 lbs. Now the total inert load carried by the two machines is otherwise about the same, and may be taken as about 200 lbs., representing the aeronaut and sundries, and it is evident that, other things being equal, the total weight of the machine should be proportional to the inert weight it has to raise, that is, in the ratio of 200 lbs. to 270 lbs. or thereabouts, and thus the greater weight of the Voisin machine is inmost part explained. If the runners of the Wright machine would do all that can be done by the Voisin mounting, then this additional weight would not be justified, but they will not do so ; the Voisin machine can rise by itself from any reasonably smooth surface ; the Wright is unable to
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