. Handbook of construction plant, its cost and efficiency. ower carries a double drum engine. From one druma line passes up the tower and over a sheave located from one-fourth to one-third its height and thence down to the bucket. Thisis the hauling line. The second line passes up and over a towerhead sheave and thence to a pulley block on the opposite side ofthe prism. This pulley block rides on a %-in. cable about 200 , stretched parallel to the prism between two deadmen, mov-ing along the cable as the tower moves. This second line is on which the scraper bucket travels b
. Handbook of construction plant, its cost and efficiency. ower carries a double drum engine. From one druma line passes up the tower and over a sheave located from one-fourth to one-third its height and thence down to the bucket. Thisis the hauling line. The second line passes up and over a towerhead sheave and thence to a pulley block on the opposite side ofthe prism. This pulley block rides on a %-in. cable about 200 , stretched parallel to the prism between two deadmen, mov-ing along the cable as the tower moves. This second line is on which the scraper bucket travels back and forth EXCAVATORS 309 across the canal, being pulled toward the tower by the haulingline and sliding back by gravity. The Tower. The tower is a framed timber structure of heightsuitable to cover the width of the excavation for which it isintended (the standard tower being 75 ft. in height). This tower Max/mum a/fa/rf ////- Sta/iSffrS/ff/rtr 0t>ir/7 rMaffrer/fr refer* /air s//*ts tre/ixZfff m*n ffr/iSs r/*S/r/Sarr/ft/e/7f/es to/fir re/t/rn ///it. S/TfCM/f. Fig. 120. Sketches Showing Operation of Field Tower Excavator. rests on a trussed platform or car which carries the hoistingengine, coal and other supplies. The tower is rigidly securedto the truss and guyed by back stays to the projecting back endof the platform. The platform or car runs on four solid doubleflange cast steel wheels, 16 ins. in diameter and 4 ins. track consists of two 90-lb. rails each spiked to 6 x 8 in. x 4ft. ties spaced 2 ft. apart and bolted to two 2 x 12 in. x 30 The engine may be any good make 10 x 12 in. enginewith double drums and two niggerheads. The hauling line is% in. and return cable is % in.; 18 in. sheaves are used. The tower is moved forward or back by a 1% in. manila linesecured to a deadman suitably placed, passing through sheavessecured to the platform and around the niggerhead. The trackis also moved ahead by the same means, the deadman beingdispensed with a
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbuilding, bookyear191
