302 



STRENGTH OF MATERIALS 



The table at the bottom of page 301 gives the strength of iron and 

 cast-steel wire rope as given by John A. Roebling's Sons. The size of 

 a new manila rope of the same strength is also given for comparison. 



STRENGTH OF WIRE ROPE MADE FROM CAST STEEL AS GIVKN 

 BY JOHN A. KOEBLINc; 



(Rope composed of six strands ;iml a hemp t-enter, seven or iiin.-tr.-n \\ in-s in i-a.-h Mr.m.l) 



Problem 190. A win- cable of the f.. 11. .win- dimensions and comi>ositio; 

 tested, ami its maximum lead found to be 5080 Ib. Diameter of cable, n.;;;; i; 

 sirands of eleven wires each; .sectional aiva . ::..-. A feX of the 



individual wires should an average strength of Jli/i.OOO lb./in.-. Kind tin- : 

 siivnu r tli diu- to the twistinir of tin- wires to form the cable, assuming that all the 

 wires have the average strength -iveii above. 



251. Strength of manila rope. The fullmviiuj tal>h- ^i\.-> tin- 

 stn-n^th of manila and sisal rupe as computed from tests made l.y 

 tlu 4 WaUM-town Arsenal.* The load in lb./in. 2 is given in cadi case. 

 This has been computi-d by mnsidfrinx the cross section .f th*- n,j M - 

 as the area of a circle of the same diameter. It will be seen fn>m 

 the table that the stress for the smaller ropes was 15,000 lb./in. 2 , 

 while for the larger ropes it was only about 7000 lb./in. 2 . This <lif- 

 tVn-nce is due in part to the greater length of yarn used in ilu 

 smaller rope. Manila rope has about t\v< thirds the stivn^h <>f 

 good Russian hemp rope.f The United States Navy test allows 

 1700 lb./in. 2 as the working strength of a 1.75-in. hemp rope. 



* Watertoicn Arsenal Report, 1897. 



t Thurston, Material* of Construction. 



