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Aviation History
1920
1920 - 0251.PDF
FEBRUARY 26, 1920 MODEL AEROPLANES NOTE.—All communications should be addressed to the Model Editor. Free-Wheel Attachments for Screws There can be no doubt that long-duration machines call for a free-wheel attachment to the screws, so that the time- length of the glide is enhanced and the gliding angle also improved. I have seen many duration models that merely come to earth in a series of phugoids once the motor is stopped, due entirely to the resistance of the stationary screws. I recently tried with satisfactory results the free-wheel arrange- Shaft ment shown herewith, consisting of a piece of tube through which the driving-shaft passes, the end of the latter being turned back into a notch filed in the trailing edge of the tube. A piano-wire saddle carries the screw blank, the ends of which are soldered to the tube. This arrangement gave 10 sees, increase in duration. The tube should be of a bore to just suit the diameter of the shaft. Another free-wheel arrangement, evolved by the writer, is for use on carved screws only, and is here shown. It 0OS5 consists of a piece of brass tube driven into the boss, and is of a sufficient bore to take a piano-wire spring, through the centre of which the shaft may pass. The leading edge of the tube is sealed. The tension of the rubber draws the cranked end of the shaft into its seating, so driving the screw, but upon the tension of the skein being released, as soon as the torsion is exhausted, the spring forces the crank from its seating, leaving the screw free to rotate. (To be continued.) Making Compressed-Air Driven Model A reader asks for the method of obtaining the proportions of a model to be driven by the compressed-air plant recently described, and also the method of treating elastic. The following reply will be of general interest :— Assuming the weight of the complete plant to be 10 ozs., and adding a further 10 ozs. for the weight of the model itself, by loading the model at 5 ozs. per sq. ft. (a good loading to employ), gives 4 sq. ft. as the total area of the supporting surfaces. Thus the main plane could be 4 ft. 6 ins. in span and of 9 ins. chord. Hence (4 x 144) — (54 x 9) leaves go sq. ins. as- the area of the smaller or stabilising surface. The length of the fuselage should be from 4 ft. to 4 ft. 6 ins. The diameter of the propeller should be 13 ins., and the pitch about 21 ins., although it is difficult to specify with regard to the last two factors, so much depends on the effi- ciency of the engine. It is by far the best plan to weigh the thrust of the model engine. By multiplying this by our or five, the weight of the model it will lift is determined. The approximate length of flight to be obtained from a model of this type is a quarter of a mile. It cannot be said that compressed air is a more efficient motive power than elastic, but it is certainly less expensive. Moreover, it requires a deeper knowledge of the fundamental laws of flight to build and fly a compressed air model than it does to build and fly a rubber-driven model. Apart from this, an engine-driven model is much more interesting to fly. The Aero Models and Research Club, Late Finsbury Park District Aero Club (Secretary, Mr. Burchall, 63, Belmont Street, Kentish Town). In the hope of giving a fillip to the sporting side of model . aeronautics, this Club is organising two competitions, to be held on the Club's flying ground, Parliament Hill Fields, on Good Friday, April 1. The Club has the ambition of becoming the strongest model organisation in the kingdom, and is determined to do all in its power to further both the experimental as well as the sporting side of a most interesting and useful pastime. There are two outstanding advantages of model aeronautics which should appeal to those who are seeking a health-giving and useful hobby. In the first place, the flying of models provides a reasonable amount of exercise in the open air, as well as providing useful work for the brain in discovering why the model does certain evolutions and in endeavouring to make it do certain other manoeuvres. In the second place, there is the indoor work of model-making, calling for the exercise of patience and ingenuity, in order to get the best results from the knowledge gained in the open air. The Club hopes, therefore, that not only will members attend in strong force at the competitions on Good Friday, but that many prospective members will make a point of turning up to see what model aeroplaning is like, and lend their valuable aid to carrying on the good work. Mr. A. E. Jones, 52, High Street, New Oxford Street, W.C. 2, is offering some prizes for an open competition with models made of materials supplied by his firm. The competitions will be held on Good Friday, April 1, at 3 p.m. sharp, and, in the event of wet weather, it will be postponed to the next day, Saturday, at the same time. Conditions for the Open Competition. (1) Flying will be for tractor models. (2) The models must be flown on the following formula :— Weight of rubber x weight of model, duration (3) There will be two hand-launched flights and one rising from the ground flight. (No special rising board will be provided.) < (4) All machines must be ready five minutes before starting time. (5) Small repairs will be allowed, at judges' discretion. (6) Entrance fee is., payable on the ground. (7) The competition will not be held unless there are six entries. Competition for Juniors under the age of 16. (1) Any kind of machine may be flown. (2) All models must be flown under the same conditions as in the open competition. (3) Entrance fee 6d., payable on the ground. There will also be a competition for members only : two hand-launched flights, one R.O.G. Prizes.Open competition : First, parcel of materials for a 3 ft. model, including finished hollow spar and propeller ; second,a pair of 12-in. propellers. Junior competition : First, one pair of 12-in. propellers,second, one dozen yards of rubber and one tin of lubricant; Members' competition : First, tractor monoplane, value£3, offered by Mr. Burchall. A silver medal has been offered by Mr. Coleman for thebest total of any six flights during the Easter meetings. Mr. White will attend the meetings to take photographs. West Kensington Enthusiasts Please Note A West Kensington reader wishes to get into touch with any model aero clubs or enthusiasts in or near his district. Address communications to W. L. Le Page, 67, Edith Road, West Kensington, W. 14. . British Industries Fair . . We are pleased to note that several of our model advertisers are exhibiting at the above Fair at the Crystal Palace. We hope to refer to the matter in greater detail in a later issue. 1 5 251
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