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Aviation History
1919
1919 - 0518.PDF
APRIL 17, 1919 M Srt&VCTH iri ca/IBtliED Tension ,1 3HEAK 0T BOLTS AT V»GYint />riCL£ OF PULL . 3nEA* BE/rtC TtUCETI BY O/iE BOLT. WAMf r- F FfCM A D DB ES«. APFHQ¥£B rt TKACX& mv OMO *: />*.-# n •> &• Cf*scK9i> my OATH Fig. 9 measure lbs. of inclined pull, and the angles of the radiating lines correspond with the angles of pull. First, the curve MNP is plotted, which gives the allowable inclined pulls as limited by the com bined stresses in the shank. That is, OM is the direct shearing value of the shank, and OP is the direct tensile value of the shank. Again, LRN is plotted, which gives the allowable variation in inclined pull as fixed by the core area of the threaded portion of the bolt. The two curves cross at N, at which point the limit, as fixed by the shank, coin cides with the value fixed by the core area. For example, at 30 deg. from the horizontal, the allowable inclined pull on a 4 B.A. bolt is OQ lbs., which equals 950 lbs. At 30 deg. from the vertical the limit is OR, which equals 850 lbs. Thus, if the value of the inclined pull is known, and its angle of inclination, the appropriate standard bolt to attach the lug to the spar or strut is immediately determinable from this chart. In certain cases the lug may be attached to the spar by two bolts, so that the shearing component of the inclined pull comes on both bolts, but all the tensions! component on one. In this case the limiting inclined pull as fixed by the shank is greater. For a 4 B.A. bolt the revised curve of inclined strength is given by LNjMi. It would hardly be practicable to rely too much on this latter case, owing to the difficulty in so fitting two bolts that each takes half of the shearing force. The really practical parts of the curves are in full lines. This chart shows that the maximum allowable inclined pull is at about 45 deg., and that then the limits as fixed by shank and core are equal. Thus the excess of area in the shank is in itself no ineffi cient use of material, apart from other practical questions which render it necessary. (To be continued.) H H a H Aerial Insurance Now that the question of insurance of machines, passen gers, pilots, goods, etc., is so very much to the fore, we shall be pleased to receive enquiries from companies or individuals interested in the subject, with a view to arranging rates, etc., under Lloyd's policies. Enquiries should be addressed to F. King, Manager, Aerial Insurance Department, 36, Great Queen Street, Kingsway, W.C. 2, who is in a position to quote the lowest market rates. 518
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