470 



ERECTION OF STRUCTURAL STEEL. 



CHAP. XIV. 



Dollys for bucking-up rivets are made in many forms to suit the different conditions. 

 Straight, goose-neck, bent, heel and club dollys are shown in Fig. 9, a ring dolly is shown in Fig. 

 10, and a corrugated iron dolly in Fig. II. Dollys for use in erecting elevated tanks are shown 

 in Fig. 1 6, and include the bar dolly, the heel dolly, the combination dolly, and the spring dolly. 



DERRICKS AND TRAVELERS. Derricks and travelers are made in many different forms. 

 A few of the more common forms will be described. 



- 



Tons 



Ties ]% 



-Lateral Ties ?i" n 



Elevation 

 STEEL VIADUCT TRAVELER 



*4^1 JL'W 



!_- -i W 



Cross Section 



/3" Manila 

 -5-?0" Sheaves 



,tf/,6 u If 



rryi ; 



t* - - --#<?'- ^55 5^/b/? 



Elevation* 



STEEL DERRICK CAR 



FIG. 20. DETAILS OF A VIADUCT TRAVELER AND A STEEL DERRICK CAR. 



Gin Pole. A gin pole, Fig. 18, is a timber or steel mast with four guys and a block at the 

 top through which the hoist line leads to a crab bolted near the bottom, or the hoist line may 

 run to the hoisting engine. The foot of a gin pole is supported by timbers which are shifted with 

 bars or on rollers. The gin pole should not be inclined more than a few degrees from the vertical, 

 and care must be used to prevent the bottom from kkking out with heavy loads. Gin poles 

 may be made of timber, gas pipe, or may be built structural steel masts. Gin poles are not 

 commonly made longer than 40 to 60 ft., but a trussed gin pole 120 ft. long has been used for 

 erecting elevated towers. The mast of a gin pole may be built up so that only two guys are 

 necessary, resulting in " shear legs" as in Fig. 18. 



Each guy is fastened at its lower end to a "deadman" (a timber, or log, or beam buried in 

 the ground). 



