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Aviation History
1932
1932 - 0507.PDF
MAY 27, 1932 30 THE AIRCRAFT ENGINEER SUPPLEMENT TO FLIGHT TOTAL 4Zff awrcugo THRUSTJ6S JYR0305 SIDE. " 300 lui FRONT yi| 500 ELEVATION |8 E.LEVWI0N g[ dc UPPER PANEL FIG. 10 IflADS IN FUSELAGE RAILS UPPER PORT UPPER STBD LOWER PORT LOWER STBD -9650 -4700 »4850 + 5900 LOWER PANEL Stress diagrams for spider mounting. Case I.—Port turn—R.H.T. and rear engine feet. Read all notation in a clockwise direction, i.e., in the literal sequence CDEF for the rear foot concentration. Now, the direction of the stress action with reference to the joint under consideration is given by tracing on the stress diagram in the correct literal sequence the direction of the line corresponding to the frame member being considered. This rule is very important and its disregard or incomplete comprehension may lead to incorrect results. A better understanding of the rule will, perhaps, be obtained by considering its application to the port front foot in Fig. 9, thus:—For member CF, the stress will act in the direction of line CF in the stress diagram, from C towards F, i.e., away from the joint. For member FA, the stress will act in the direction of line FA in the stress diagram, from F towards A, i.e., towards the joint. To determine the sign of the stress. If its direction is towards the joint the stress in the member is compressive, and vice versa. Finally, the allowance must be made for the fact that certain members are not in the plane of the paper. Thus, the bearer CF is in the plane of the paper and the load read from the stress diagram is consequently a true load. In the case of members DE, EF and FA, however, which are all inclined to the plane of the paper, the loads given by the stress diagram are apparent only, and the true load must be laid off against each apparent load as shown by DE,, EF2 and F,A in the port stress diagram. The diagrams for the spider mounting shown in Fig. 10 comprise the successive application of the simple triangle of forces. The sequence may, however, be a little confusing and the steps involved are enumerated below, thus: — (i) Combine into resultants the external loads at nodes A, a, B and C. (ii) Resolve these resultants into components in the planes of the legs of the spider, (iii) Allow for obliquity of the legs of the spider, obtaining the true loads in the legs and the induced loads in the plane of the bulkhead panel. 468 (iv) Transfer all components of the true loads in the legs, as applied at nodes D, d, E and e, into the front fuselage structure. 15. Loads in a Spin Although this case is not laid down in A.P. 970 for stressing purposes it is often as well to investigate for this condition, particularly in the instance of ultra modern high-powered high-speed fighters and day bombers. The whole question has been most ably dis cussed by Mr. D. Williams, B.Sc, A.M.I.Mech.E., in " The Aircraft Engineer " dated August 28, 1931, under the heading " Forces on the Engine Mounting of a Spinning Aircraft," to which article present readers are referred. TECHNICAL LITERATURE 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. THE FLOW OF A COMPBESSIBLE FLUID IN THE NEIGH- BOUBHOOD OF THE THBOAT OF A CONSTBICTION IN A CIBCULAB WIND CHANNEL. By S. G. Hooker, D.I.C., Armourers' and Brasiers' Research Fellow. Presented by Professor L. Bairstow. R. & M. No. 1429. (9 pages and 7 diagrams.) May, 1931. Price 9d. net. The symmetrical flow of a compressible fluid through a tube Is investigated. In Case I there appears to be a limit to the velocity at the centre of the constriction in order that such a type of flow can exist and this limit corres ponds to the attainment of a maximum velocity in the field of l-024a. Whether this excess over the velocity of sound is an actual excess or due to numerical limitations In the method of solution has not been determined. g
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