472 



ERECTION OF STRUCTURAL STEEL. 



CHAP. XIV. 



Guy Derricks. A guy derrick, Fig. 18 and Fig. 19, has a vertical mast guyed with three or 

 more guy lines, and has a boom which carries blocks and a fall line on the upper end. The boom 

 is raised and lowered with rigging called "topping lines" or "boom lines." The load is raised 

 by rigging called "fall lines" or "falls." The hoisting line may be run down the boom to a crab 

 or to the hoisting engine, or the hoisting line may be run through a "rooster" placed on top of the 

 mast and then to the hoisting engine. Guy derricks may be swung in a full circle, either by hand 

 or by means of a bull wheel operated by a line from the hoisting engine. 



"A" Derrick. The "A" derrick or "Jinniwink" derrick is shown in Fig. 18. "A" derricks 

 are used for light hoisting up to three to five tons. The "A" derrick is a simple form of the stiff- 

 leg derrick. 



Stiff-Leg Derrick. The stiff-leg derrick has a mast braced by "A" frames set at right angles 

 to each other, Fig. 18 and Fig. 19. The loads may be lifted and the boom raised and lowered 

 by means of a crab or by a hoisting engine. The stiff-leg derrick has a free swing of about 240 

 degrees. The mast may be turned by hand or by means of a bull wheel operated by a line from the 

 hoisting engine. Details of a 1 2-ton timber stiff-leg derrick are shown in Fig. 21. Stiff -leg 

 derricks of large capacity are now commonly made of structural steel. Details of a steel stiff-leg 

 derrick are given in Fig. 29. 



-c. to c. Oirders ^ 



FIG. 22. DETAILS OF A GALLOWS FRAME. AMERICAN BRIDGE COMPANY. 



Boom Travelers. The mast of a derrick may be supported by the framework of a traveler, 

 Fig. 1 8. The traveler may be made one or several stories in height. The booms may swing or 

 may be fixed to raise and lower in one plane, and may be used single or in pairs. Boom travelers 

 are commonly used in erecting train sheds, and structural steel buildings. Details of a steel boom 

 traveler are given in Fig. 28 and Fig. 29. 



Viaduct Travelers. An overhang traveler for erecting a high steel viaduct is shown in Fig. 20. 



Gallows Frame. A gallows frame or a transverse bent as shown in Fig. 22, is used for erecting 

 plate or riveted girders. The gallows frame is guyed fore and aft with steel cables. Gallows 

 frames are commonly used in pairs or a gallows frame is used with a stiff-leg derrick. 



Through or Gantry Travelers. A through or gantry traveler consists of two or three trans- 

 verse bents or "gallows frames" braced longitudinally and is carried on a track supported on the 

 falsework and placed outside of the trusses. The traveler has a clearance such that it can be 



