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Aviation History
1909
1909 - 0732.PDF
NOVEMBER 13, 1909. tenants will have the exclusive occupation of the sheds, and the right to use the interior of the track as an aviation ground upon all occasions except when the track is required for race meetings, or when it would be, in our opinion, undesirable to have both aviation and motoring proceeding at the same time. "Aviators will have the right to use the ground already specially levelled and prepared, and to pass over the other portions inside the track which are cleared, and over which it is intended by degrees to extend the levelling and smoothing. "The provision of workshops and preparing works for tenants will be a matter for consideration, and proposals in regard to this will be entertained. " For the rent of each shed, and the facilities above described, each tenant will be charged either— " 1. .£100 per annum, payable in advance on signing an agree- ment ; or " 2. j£io a month, payable monthly in advance for an agreement of not less than six months' duration. " The construction of sheds is being proceeded with, and three sheds are expected to he ready in a fortnight, but other sheds will be built within four weeks of arrangements being made with intending tenants, and preference will be given in the order of application. " The satisfactory experience of the last few days, and M. l'aulhan's expression of opinion on the subject, show that the Brooklands ground, as at present laid out, is eminently suitable for aviation, and that the improvements now being made will render it still more valuable for this purpose. " I shall be glad to hear from you at your earliest convenience whether you wish to become a tenant on the terms mentioned above." PROPELLERS WANTED. To the Editor of FLIGHT. SIR,—Can you tell me whether it is possible to obtain a pair of propellers, one to be used above the other, 8J ft. in diameter, revolving in opposite directions, for use in a helicopter, that will develop enough thrust to raise a weight of 675 lbs. with a 6o-h.p. motor, r.p.m. 1,200. The propellers are to be encased in a cylinder open at both ends. Please print this inquiry, as I am one of your American subscribers. 7 Verytruly yours, 250, Vance Avenue, - E. F. STEPHENSON. Memphis, Tenn., U.S.A. SHERTH A SANTOS DUMONT DETAIL. To the Editor of FLIGHT. Siu,—I am making a one-sixth scale model of the " Demoiselle," and everything is clear to me from your excellent details and phoio- graphs except one point, which I should be much obliged if you could explain to me by means of a short description or rough pencil sketch, viz., the position and fixing method of the vertical member that controls the eleva- tion of the tail. It appears that there are oval struts just about where it should come, and it seems to me that it should be split to clear the top bamboo of frame. I should think it ought to be pivoted on the same hori- zontal line as joint of tail (eleva- tor part), although from diagrams it appears to be pivoted level with bottom bamboos of frame, hence, perhaps, the use of the spiral spring. However, this is conjecture, and you probably know, so I thank you in antici- pation. Yours faithfully, T. T. SALTER. West Kensington. [The above sketch which we have prepared will perhaps make the constructional detail referred to in the above letter clear to our correspondent. It should be mentioned that the principal vertical member in the diamond frame there shown is an oval sectioned steel tube, and extends from the skid below to the upper joint in the frame. The short mast which projects above this joint is a separate member.—ED.] ~V - PITCH AND TORQUE." To the Editor of FLIGHT. SIR,—I am anxious to find the speed of a model aeroplane, but do not understand what is meant by the " pitch " of a screw ; also what is meant by " torque." Could you please inform me as to this? •-;.-• ,-•• >-• -•, - "... Thanking you in anticipation. . -•••-• ..--:.„...• Yours faithfully, Sutton Coldfield. FREDK. C. HARPUR. [The pitch of a propeller is the amount which it would travel forward in one revolution if it were moving in a solid medium incapable of slip. In other words it is equivalent to the pitch of a steel screw, which is the measurement along the axis of the distance between adjacent convolutions of the same thread, measured from apex to apex. In actual practice an aerial propeller imparts a sternward velocity to the air in which it works, and consequently the speed of the machine per revolution of the propeller is less than the pitch of the screw by an amount equal to the slip. PITCH TORQUE = Torque is a term defining a force which produces twi>t. It is pressure or weight acting through a leverage, and is thus a compound unit capable of being expressed in lb. feet or lb. inches, according to the dimensions most convenient to the work. If the power trans- mitted by a shaft be resolved into the work done per revolution, that value divided by 2ir will give the torque on the shaft. The torque is a measure of the stress imposed, and the strength of a solid circular- section shaft is proportional to the cube of its diameter. Hence, D:i multiplied by a constant appropriate to the material employed must always be greater than the torque to which it, the shaft, is subjected.—ED.] AERO MOTORS. To the Editor of FLIGHT. SIR,—Judging from the report of the recent Paris Show, the majority of aero motors in France—as elsewhere—appear to be purely car motors, as, although of lighter weight, there is nothing to show that they are specially adapted for aero work. The few rotary-reciprocating engines certainly are a departure from stereotyped design, but [ have long wondered why no firm has yet produced an aero engine with cank-shaft and pistons as in a car motor, but designed to run in the inverted position, which in my view is the better way, and particularly suited to monoplanes, in nearly all of which the pilot is on a level with the carburettor,;so that, if it fires, the flames stream back on to the pilot—-as happened at Rheims to M. Bleriot, who was flying low at the time or the result must have been more serious. Inverting the engine would bring the carburettor below the aviator, and, incidentally, would lower the centre of gravity. It also admits of a very compact arrangement of the tanks and radiator owing to the low level of the carburettor and water-jacket, into which the cooled water would enter close to the valves. In such an engine the cylinders would project into the crank-ca e to keep the oil drainings out of the cylinders, while the oil-sump could conveniently be formed in the gear end of the crank-chamber, the cover of which may be of light sheet material secured after the manner of a car bonnet, and as readily opened, giving instant access to the big-ends, main bearings, oil-pump, &c. There need be no lubrication trouble, as witness the success of the Gnome rotary-reciprocating motor, in which all sorts of lubrica- tion troubles were prophesied by the "experts." If, however, it be found necessary to cover the cylinder ends in order to prevent over lubrication, a very simple form of cover could be made of a thin rectangular sheet of metal, bent to form an arched roof over the cylinders—as high as the big-ends would permit—and secured to the 734
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