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Aviation History
1933
1933 - 0869.PDF
75 OCTOBER 26, 1933 THE AIRCRAFT ENGINEER SUPPLEMENT TO FLIGHT synchronise on the test-bench by running alternate mag netos and adjusting timing until no fall in engine revo lutions was noted. When the engine has finally been assembled it is taken to the test-house and put on the Heenan & Froude dynamometer, referred to above. In the test-house pro vision is made for measuring petrol consumption on two dual flowmeters, which can be used singly, in tandem or in parallel, thus giving a cross-check on fuel consumption. Alternative forms of oil tanks are provided for dry sump engines, whether scavenged or for gravity-return type, and temperature gauges are fitted for both inlet and outlet. It is also possible to control the inlet oil temperature by electric heating and circulating water. Thermocouples and calibrated galvanometers are used for determining the temperature of cylinder heads or any other predetermined spot. The petrol and oil tanks used in the test-house are so arranged that for long continuous runs they can be replenished without interfering with the gauges or with the temperature. The various data taken during test- runs are given on report sheets, one typical sheet being reproduced in one of our photographs. By way of an item of topical news, it may be men tioned that the cylinders of Mr. Ulm's Wright engines were re-ground by Airwork Engine Service, Ltd., before he started on his record flight to Australia. TECHNICAL LITERATURE "MARINE AIRCRAFT DESIGN" HITHERTO there has been a lack of concise literature on the subject of the design of seaplanes and flying- boats. The subject is one of the very greatest import ance to the British Empire, but it has not so far received the attention which has been showered upon the landplane, the reason presumably being that for every designer of flying-boats there are a dozen or more designers of landplanes. In research, too, the quantity of information available to the student or the designer who wishes to become familiar with the particular problems of marine aircraft is relatively small, and only to be found scattered throughout various Government and other publications. While it could scarcely be claimed that " Marine Aircraft Design," by William Munro, A.M.I.Ae.E., published by Sir Isaac Pitman & •"ions, Ltd., and obtainable from FLIGHT Offices at 20s. 6d., post free, provides complete information con cerning all the difficult problems to be solved in the design of a flying-boat or twin-float seaplane, the book does serve as a very excellent introduction to the sub ject. Mr. Munro has had practical experience of marine aircraft design both in this country and in the United Mates, and is thus well equipped for compiling such a nook. Some of his work will be familiar to our readers irom articles published in THE AIRCRAFT ENGINEER, but the book contains a great deal of material not pre viously published, or at any rate not readily accessible. Wr. J. Laurence Pritchard, Hon. F.R.Ae.S., Secretary °r the Royal Aeronautical Society, has written a fore word to the book, in which he calls attention to the part ''•Inch marine aircraft are bound to play in the future °f the British Empire. He points out that the book is "ininently practical, a book written by an engineer. Marine Aircraft Design " is divided into two sec tions, the first dealing with flying-boats and the second with floatplanes. In between them is sandwiched a chapter on Wine Design bv B. S. Shenstone, M.A.Sc, VF.R.Ae.S. " I he general principles of hull design are dealt with "rst, and then the reader is carried by stages through strength of hulls and hull construction to stability of nying-boats on the water. A somewhat similar scheme 1072 has been followed in the section dealing with float planes. A set of data sheets completes the book. Under the chapters dealing with the strength of hulls and floats, a useful guide is given to the gauges of sheet used in various parts of the hull, and which experience has shown to give the necessary rigidity. The calculation of metal-skin hulls is still a long way from being an exact science, and experience and common sense must be relied upon to bridge the many gaps in our knowledge. " Porpoising " is a vice which many seaplanes and flying-boats have been found to have in the past, and the subject is of such a complicated nature that there is no hope of being able to calculate beforehand the behaviour of a flying-boat under any of the varying conditions which it may be called upon to meet. Possibly that is why Mr. Munro has made no attempt in his book to explain " porpoising," and, in fact, merely refers to it in passing. The phenomenon is not even included in the index. It seems a pity that Mr. Munro has not devoted a few pages to this subject. No one would expect him to produce formula) guaran teed to prevent porpoising, but the reader is entitled to expect a statement of the general nature of porpoising, the features which tend to produce it, and the design remedies which have been found to reduce it. Apart from the sketchy treatment of fore-and-aft stability on the water, the main criticism which can be levelled against the book is that it appears to favour, by the mass of details, if not by actual statement, the type of hull which has straight-line sections in the body plan. This type of hull is by no means typically British, and one suspects that the author has been led to include so much material dealing with this type because he became familiar with it during his con nection with the design of the Towle amphibian in America. In spite of the shortcomings indicated, " Marine Air craft Design " is a book which should serve to give the student and the designer without previous experience of marine aircraft design a very sound, if not quite com plete, insight into the mysteries of the combined arts of the aircraft designer and the naval architect. SUMMARIES OF AERONAUTICAL RESEARCH COMMITTEE REPORTS These Reports are published by His Majesty's Stationery Office, London, and may be purchased directly from H.M. Stationery Office at the following addresses: Adastral House, Kingsway, W.C.2; 120, George Street, Edinburgh; York Street, Manchester; 1, St. Andrew's Crescent, Cardiff; 15, Donegall Square West, Belfast; or through any Bookseller. APPLICATION or A METHOD TOR DETERMINING THE STRESSES IN BRACED FRAMEWORKS. By L. Chitty, A.F.R.Ae.S. R. & M. No. 1528. (36 pages and 2 dia grams.) October 12, 1932. Price Is. 9d. net. A tubular framework, consisting of longitudinal and crossed diagonal members connected by pin joints to a series of radially braced transverse frames (or bulkheads), may present a highly redundant structure, if all the members are capable of withstanding both tensile and compressive forces. When such a structure, consisting of several bays, is subjected to external loads acting at the joints of the terminal bulkheads, strain energy methods for determining the stresses in the members are out of the question, and other methods hitherto suggested have involved restricting assumptions either (a) as to the distribution of the total applied load among the joints of the terminal bulkheads,* or (6) as to the rigidity of the bulkheads through out the tube.t In a paper to the Royal Society.t Professor R. V. Southwell has now out lined a general method for determining the stresses in the members of such a structure when the external loads (or the displacements) at the joints of the terminal bulkheads are specified in any arbitrary manner, and this method involves no restricting assumptions as to the rigidity of the bulkheads. In the first part of the present paper this method is applied to a particular structure—the fully braced hexagonal tube which waB constructed and tested * R. & M. 791. " On the determination of stresses in braced frameworks." Part III.—R. V. Southwell. t R. & M. 1427. "Primary stresses in the hull of a rigid airship."— L. Chitty and R. V. Southwell. See also R. & M. 800, Appendix V, for a particular case. t Proc Roy. Soc. A, Vol. 139, 1933. "On the calculation of stresses in braced frameworks."—B. V. Southwell, F.R.S. (R. & M. 1526.) s
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