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Aviation History
1909
1909 - 0336.PDF
JUNE 5, 1909. CORRESPONDENCE. *,* The name and address of the writer (not necessarily for publication) MUST in all cases accompany letters intended for insertion, or containing queries. "ELASTIC MOTORS." To the Editor of FLIGHT. SIR,—Referring to the letters in your last issue, with respect to the models, the length of flight of Mr. Webb's models are good, but not uncommon. I have seen one of the larger (not largest) kind of Clarke's Flyers travel 600 ft. (200 yds.), and some have, I believe, travelled over 1,000 ft. The range of flight depends chiefly on the machine being so built as to travel swiftly (offering minimum resist- ance), and the elastic motor strand being long, so as to allow of many turns, some 250 to 300. The manner in which the power (torque) of the elastic increases with the number of turns is interesting. The following is the mean of several experiments :— Turns 15, 30, 50, 70, 100, proportional to I, 2, 2-125, 2'25> 3- We thus see that the twisting force is by no means proportional to the number of turns, especially after a certain number of turns have been given. This is chiefly because the elastic has been twisted or stretched beyond the elastic limit. This is why new elastic, the first time it is used, gives some- times as much as 20 per cent, better results than after- wards. The following are the times taken by a wooden screw one foot diameter to run down 30, 60, 90, 120 turns re- spectively, viz., 2-5, 3-5, 4-5, 5-5 seconds approximately. About 10 to 15 seconds appears to be the limit for swift-running elastic motor-driven screws. The length of flight, therefore, depends on an initial high speed by means of a suitable launching apparatus and the continuing of the same by means of strongly-driven and rapidly-rotating twin screws, and a small and efficient sustaining surface. The best rubber to use is the thin black Ty to \" in thickness; as to the best place to get it consult a Trades Directory for list of rubber dealers, and get the nearest to procure for you, say, so many dozen yards. You should then get it fresh ; never buy rubber that has been kept in stock. Keep it when not in use in the dark. Model flights in a large hall differ greatly, though not, of course, so much as out of doors. It is impossible to launch a model twice in exactly a similar manner. Moreover, for any particular flight the model is not in quite the same shape or condition as it was for the one before. To claim to have solved any question of aerial balance as applied to a full-sized machine by means of a small model is absurd, though the writer knows of a score who have done so. The conditions are totally different. I am glad to see from advertisements in last week's number that the Economic Electric Company have followed out my suggestions, and brought out an electric aeroplane motor. Yours very faithfully, Streatham, S.W. V. E. JOHNSON. BRITISH INVENTIONS AND FOREIGNENCOURAGEMENT. To the Editor of FLIGHT. SIR,—Re Mr. Holdsworth's idea about capitalists falling over each other to put money into an invention, this is the vision of a young inventor, and is seldom, if ever, fulfilled. Just to show how anxious capitalists are to put money into an invention, I have pleasure in giving you an extract from a letter of a would-be investor. In the first place I have something to sell ; my model was successful at the Aero Exhibition ; the principle is good and sound; I have a J-size model to scale in course of construction, also well worked-out plans for the full-sized machine; a fair plant of machinery for engine building, in fact, machines could be built throughout in my own shop at an estimated cost of£ 3i I think Mr. Holdsworth will agree that the above is something to show to an investor. Well, this is one of the magnificent offers to invest ^50 in a company of .£1,500 capital on the following conditions:— (1) That the patent is perfectly sound and has not been antici- pated in any way. (2) That I be styled the constructor-in-chief of the aeroplane, or works manager, to guarantee the "investor" a first-class berth on the floatation of a larger company. (3) That I am to be the first to use and thoroughly test the machine and when same has proved thoroughly safe and reliable, it is guaranteed that the " investor " is to be the second person to make a flight on the machine. These are the terms of his offer. He no doubt forgot to insert the clause that if the machine was a failure his money should be returned in full. I consider Mr. C. D. Clayton's letter, May 8th, re Foreign Capital, more than probable. Yours respectfully, Birmingham. ALFRED P. MAXWELL. P.S.—Perhaps Mr. Holdsworth was thinking of foreign capitalists, evidently not English speculators ? EFFICIENT PROPELLERS-A CHALLENGE. To the Editor of FLIGHT. SIR,—I have read a great many letters and advertisements lately in the technical press by various propeller designers all claiming to have designed aerial propellers which are remarkably light and highly efficient. Now I think something ought to be done to find out whose propeller really gives the best thrust for a given weight and horse-power. I propose to set the ball rolling by backing my design against all-comers to the extent of .£5, that it will give the best thrust for a given weight and horse-power. It is a left-handed propeller made of metal, driven by ^-h.p. electric motor ; although it weighs just under 5J ounces, the thrust given runs into pounds. Anyone who takes up my challenge can make their propeller of any pitch, diameter, surface, or shape they fancy, it must be made of wood or metal, and not exceed 5J ounces in weight without the boss, and not to be a copy of my design, the boss to fit a f shaft, the propellers to be tested on an |-h.p. electric motor under equal conditions by some disinterested person. The challenge to remain open for four weeks from date of publication. In conclusion, I trust that some of the many sporting propeller experts will take me up at once and relieve me of my ^5. Surely it is not a difficult matter for a man who knows bis business to design and make a propeller which will conform to the above simple regulations. If my challenge is not accepted, I trust prospective buyers of propellers will consider my design before deciding to buy any which are advertised. Yours faithfully, WILLIAM COCHRANE. MODEL FLYERS—A CHALLENGE. To the Editor oj FLIGHT. SIR,—I'have read with interest the description of Mr. Webb's wonderful machine by Mr. Wright. Now I consider that my patented machine, No. 7205, 1908, is a fair sample of what a model should be, and if it could be arranged I should be pleased to fly in private competition against any machine at present on the market, either with the wind, against the wind, in a straight line across the wind passing over given points, or in a curve passing approximately over given points, the models not to carry less than 5 ozs. to the square foot of canvas. Such a trial as this would bring out the good points prominently of such a machine as Mr. Webb's, and might perchance teach others something, and I shall be pleased if you would insert this in your paper as a challenge against all comers, as it should be an interesting experiment, and prove the value of assertions made in a paper with regard to the peculiar properties of any particular machine. Yours very truly, June 1st. MONTFORD KAY. CLOCKWORK MOTORS FOR MODELS. To the Editor of FLIGHT. SIR,—Referring to Mr. Angus's letter in yrtur valuable paper, we beg to say that we have been experimenting for some time past with clockwork motors for driving model aeroplanes, and have now designed the lightest possible arrangement, using a very powerful spring, which we are placing on the market with a guaranteed thrust, and time of running, that may be useful to him. We are also manufacturing all the various sundries required for building model planes. Yours truly, London. THE UNIT ELECTRICAL FIRM. Aeronautical Patents Published. Applied tor In 1908. Published May 2jth, 1909. 9,970. V. HU.MUERT. Flying machines.20.095. W. F. HOWARD. Aerial toy. 20,694. A. F. J. DOUTRE. Flying machines or aeroplanes. 338
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