84 



STRESSES IN A DERRICK. 



Art. 62. 



the center of moments being in U 2 directly above joint 5. Now 

 Ld being equal to Ily^ we have 



D t d' = H ( Vt -y t ) 



Drawing a line through the upper extremity of 7/ 4 parallel 

 to string 6,* it cuts off, on t/ 5 , the distance y^y 4 ; constructing 

 two similar triangles upon this distance, Z> 4 is determined. 



62. Stresses in a Derrick. The crane or derrick 

 shown in Fig. 49 is usually supported by several wire rope guys 



attached at B and running down to anchorages at some dis- 

 tant points, or by two stiff legs attached at the same point. 

 Thus in the common derrick the reaction at B is not horizontal. 



