. Principles and design of aëroplanes . ■ Use feet and pounds for measure-ments, and the result will be in foot-pounds turning or bending moment. The resisting moment of the framewill be as follows (rectangular frame) : 2 X pull or push in one bar (lbs.) Xdepth of frame (feet) = bendingmoment. Using the greatest bending moment,we have then: n, i. i( pull in bottom bars ) _( or, push in top bars ) greatest bending moment2 X depth of frame If the frame is triangular, 64. 65 (Push in top bar X S depth) + 2 (pullin each bottom bar X A depth) =bending leads to the following simple rule:
. Principles and design of aëroplanes . ■ Use feet and pounds for measure-ments, and the result will be in foot-pounds turning or bending moment. The resisting moment of the framewill be as follows (rectangular frame) : 2 X pull or push in one bar (lbs.) Xdepth of frame (feet) = bendingmoment. Using the greatest bending moment,we have then: n, i. i( pull in bottom bars ) _( or, push in top bars ) greatest bending moment2 X depth of frame If the frame is triangular, 64. 65 (Push in top bar X S depth) + 2 (pullin each bottom bar X A depth) =bending leads to the following simple rule: Pull or push ) _J> x bending moment,in rods ) 4x depth For the transverse frame we have: Greatest bending moment === (L3 - W6) x-|, or (L4 - W8) x |- The monoplane type of machine de-vised by Professor Langley is also adoptedby some experimenters, but not withsurfaces in tandem as he had them. Inthis there is a central girder, and thetransverse planes (which are not super-posed in pairs) have framings which arejointed with tee-pieces into the centralshaft. The frames are stiffened by cross-struts and stay-wires fixed to the endslike the trussed beams used in travellingcranes. Steel is preferable for this type 66 of frame. Aluminum is of no great ad-vantage, as strength for strength it isvery little lighter, and much more ex-pensive and difficult to procure. As regards the joints of frameworkit is perhaps best to have specially castjunction-pieces, although
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