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Aviation History
1931
1931 - 0387.PDF
Supplement to FLIGHT ENGINEERINGSECTION Edited by C. M. POULSEN April 24, 1931 CONTENTS PAGX A Graphical Method of Stressing Aeroplane Spars. By D. Williams, B.Sc, AJVIJJVIech.E 25 Shock Absorbers for Aircraft Landing Gear. By W. S. Hollyhock ... 27 In the Drawing Office... ... ... ... ... ... 31 A GRAPHICAL METHOD OF STRESSING AEROPLANE SPARS. By D. WILLIAMS, B.SC., A.M.I.Mech.E. (Concluded from p. 21) II. Change of Moment of Inertia of Section In case I it was seen that the locus line was shifted parallel to itself at each boundary line. A change of moment of inertia I, which results in a change in ;x, produces no such shift, but merely has the effect of rotating the locus line through an angle depending on the magnitude of the change in \x. This will be illustrated by taking a main bay AB, in which two changes of I occur, as shown in Table II. Referring to Fig. 4, draw the positive and negative sectors with angles a1; a2 and a3. Assume OmA positive, as usual. Draw the perpendicular at m^ to give the first locus line W2 TABLE II. B ASSUMED THAT ex CC, I a, - ZERO | and the points fx and lv With /, as pivot ttt is rotated to the position ll2 by taking any point y on Ult dropping the perpendicular yy1 on f-f, finding a point y2, such that y&Jyyi = V-Jv-v and finally joining yjv The latter produced cuts the next boundary line in gx, and the base line BJB in nx. At gx ll2 is rotated in a similar way (i.e., z2z1/zz1 = !X2/n.3) to give the last locus line lls, which cuts BXB in n2 and makes an angle G with it. This angle is measured. This time the movements of the locus line, as recorded by its point of intersection with BXB, are not 362a
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