HOISTING TACKLE. 



447 



nomical and satisfactory than manila rope. Data on crucible cast steel hoisting rope are given 

 in Table III; and data on plough steel hoisting rope are given in Table IV. A factor of safety 

 of 4 should be used for working loads only with derricks or hoists that are not in continuous 

 action. For pile driving and for continuous hoisting a factor of safety of 6 should be used for 

 working loads. Wire ropes used in hoisting are commonly |, j and { in. in diameter. The smaller 

 di.imi IT> art used for guy lines. For standing guy lines a cheaper wire rope will usually be 

 found satisfactory. Bending stresses in wire ropes are given in Fig. 7, Chapter X. 



HOISTING TACKLE. Blocks for both manila rope and wire rope are made with wooden 

 shells and with steel shells. Blocks up to 12 to 15 tons capacity are commonly provided with 

 hooks; blocks for heavier loads are provided with shackles. Blocks should be well built with 

 adequate bearings and carefully worked out details. The common types of blocks are shown in 



Fig. 3- 



Data on wooden blocks for Manila rope as used by the American Bridge Company are shown 

 in Table V. 



Data on steel blocks for wire rope as used by the American Bridge Company are shown in 

 Table VI. 



TABLE VI. 

 DATA ON STEEL BLOCKS FOR WIRE ROPE. AMERICAN BRIDGE COMPANY. 



Rigging. The rigging for lifting loads with wire rope are given in Fig. 4, and for manila 

 rope in Fig. 5. These data are based on experiments made by the American Bridge Company, 

 and have been adopted as standard by the American Bridge Company and the McClintic-Marshall 

 Construction Company. 



TABLE VII. 

 RATIOS OF LOAD TO PULL IN LEAD LINE. 



