HOISTING ROPE. 



proceeds. Steel tanks are commonly erected from a movable platform suspended inside the 

 tank. A movable swinging platform fur ih riveters is also swung outside of the tank. 



ERECTION TOOLS. The tools and appliances used in the erection of structural steel vary 

 so much that it will only be possible to give a brief summary together with data not ordinarily 

 av.iil.iMr. Many of the tools and appliances used in the erection of structural steel are of standard 

 contruction and may be purchased direct from dealers, so that a detailed description is not neces- 

 sary. 



Design of Erection Tools. For the design of hoists, derricks, cranes, crane hooks, and other 

 tools used in bridge erection, see Hcss's " Machine Design, Hoists, Derricks, Cranes," published 

 by J. B. Lippincott Company. 



Hoists. Hoisting engines may have the boilers attached or may be detached. A self-con- 

 tained steam hoisting engine is shown in Fig. I. Gasoline or electric power may be used to 

 advantage where available. For light hoisting the 4-spool engine is commonly used. Data for 

 tho standard hoisting engines used by the American Bridge Company are given in Table I. 



Winches and Crabs. For light hoisting winches or crabs operated by hand power may be 

 used. A crab is attached to the mast or boom, while a winch is self-contained. Views of a crab 

 and of a winch are shown in Fig. I. 



HOISTING ROPE. Either manila rope or wire rope may be used for hoisting. 



Manila Rope. Only the very best new manila rope should be used for hoisting, as manila 

 rope rapidly deteriorates when used and commercial manila rope varies greatly in strength. The 

 weight, ultimate strengths and safe working loads for manila rope are given in Table II. Working 

 loads with a factor of safety of three should only be used with new rope of the best quality. 



TABLE I. 

 STANDARD HOISTING ENGINES. AMERICAN BRIDGE COMPANY. 



TABLE II. 



MANILA ROPE. ULTIMATE STRENGTH, WEIGHT AND WORKING STRESS OF BEST 



MANILA ROPE. 



