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Aviation History
1918
1918 - 1409.PDF
neutral axis, namely, the third. Throughout this seriesit will be noted that the edge effect modifies the colour pro- gression for a narrow strip at each edge. Fig. 19 shows the point of inflection with 40 1b. loadas before, by taking the mean position between the wedge of colour at top right and bottom left corners. The paleorange colour over the greater part of the surface indicates nearly uniform compressional stress caused by the end thrust. FIG. 21. If there had been no end thrust, the colour would have been ajuniform dark grey tint, as seen in the neutral axis in Fig. 13. > Figs. 20, 21 and 22 illustrate the use of a tapered test piece under known stresses. The test piece is described in Section 1. Fig. 20 shows the test piece under no "tension crossing DECEMBER 12, 19x8 the strained beam. It -will be noticed that the neutralaxis has not been displaced apart from a certain dis- tortion caused by the test piece not being in the sameplane as the beam. Fig. 21 shows the test piece so strained as tott neutralisethe first order of red, the result being that the neutral axis has apparently shifted down the breadth of one colourband. Fig. 22 shows the test piece adjusted so that the secondorder of red is neutralised, the result being that the neutral axis has apparently shifted down the breadth oi twocolour bands. In both cases the stress at the neutralised band of the test piece is equal to the stress in the model spar. Fig. 23 shows the isoclinic lines and the isochromaticlines in the neighbourhood of two bolts piercing the beam and screwed up with moderate tightness. FIG. 22. Fig. 24 shows the result of overstraining the bolts(the loads in both cases being 40 lbs. distributed). The dark lines are no longer neutral axes, but a method can beworked out for evaluating the stresses in these two cases. For the present it is sufficient jo remark that the conditionof uniform stress gradient in the main portion of the beam is completely altered in the neighbourhood of the bolts, but isvery nearly restored ^at a distance equal to the depth of the beam. i^To be continued.) . British Flax for Aeroplane Fabric IN the report of the Development Commissioners forthe year ending March 31st, 1918, it is pointed out that owing to war needs has led to such an increase of flax-growingthat it is no longer of an experimental or educational nature. In the previous years the Commissioners granted ^6,275to the British Flax and Hemp Growers' Society, and in 1917-18 a supplementary grant of ^15,450 was made for an extensionof the society's work in order to ensure a future supply of material for the prodnction of aeroplane cloth and to increasethe growth of linseed as feeding stuff for stock. This was followed by an application for an advance ef £205,700, ofwhich £200,000 was by way of a loan for the initiation of an extended programme for the cultivation of flax in GreatBritain and its production into fibre. The growing of flax for fibre on the extended scale carries the undertaking outsidethe experimental or demonstrative sphere appropriate for aid from the Development Fund, and after the applicationreferred to had been received arrangements were made for the whole of the society's flax-growin§ work to be takenover by the Board of Agriculture. '".-.' ;•—?-»,:.•;.,. An Australian Aerial Survey INFORMATION to hand from Melbourne is to the effectthat Mr. Reginald Lloyd of London has formed a company to finance an aerial survey of a route between Australiaand England, via Sydney and Port Said, and to locate landing and relay stations. Although the movement is chiefly ona business basis, Generai Legge, Chief of Staff, is supporting the scheme on the ground that it may provide the nucleusof the future aerial militia. Map of the U.S.A. ADVANTAGE is being taken by the U.S. authorities ofthe training of U.S. aviators in photographic work to secure a photographic map of certain sections of the country. Thefirst map to be completed is that of th« territory in and around Fort Sill, Oklahoma, It is made up of a mosaic of 4,000separate prints, the map covering a space 16 ft. long and 6 ft. wide, reproducing a ground area of 310 sq. miles. Thismap shows highways, lanes, trees, fences, railway-lines and other landmarks. This work was completed in a little overa month, and three machines went up each day to secure the negatives. Each machine exposed 72 during a tripaveraging an hour-and-a-half. No Show in New York ?JUST before the Armistice was signed, the American Manufacturers' Aircraft Association decided to abandontheir arrangements for the holding of the annual show during the coining year, in view of the necessity for devoting alltheir time and energy to Government requirements. The altered situation may, however, cause this decisionjto bemodified. . . 141 o "-T
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