Pocketbook of Useful Formulæ and Memoranda
for Civil and Mechanical Engineers

437 OF ENGINEERING FORM ULÆ. . Cranes. Computation of Stresses by Graphic Construction. With any convenient scale dray’ A B parallel to the sus- pending chain and equal to the load W; also draw AC parallel to the back chain aad t= W ; coiApl'ete the paral- lelogram by tjie lines CD, BD drawn parallel to AB and A O respectively. Then the line A ß represents the intensity of the stress on the pin at A. From I) draw a line parallel to the stay until it intersects the line <jf the jib at E ; then D }£ represents the stress on the stay, and A E the stress on the jib. In this diagram no account has been taken of the stress produced by the weight of the crane itself. . A D being the resultant of the lines A B and A C will form with D E two sides of the parallelogram of furcua for the crane.