Engineering Wonders of the World
Volume I

THE BRIDGES OF NEW YORK CITY. 269 moment this had been done, the sheave was ready for a return trip, and, taking wire from a reel on this anchorage, it strung a third and fourth wire on its way back. During the first trip of the sheave, say from Brooklyn to Man- hattan, the other side of the travelling rope was carrying its own sheave with wire from Manhattan to Brooklyn. This double action being maintained on every trip, each move- ment of the rope had the effect of spinning > 10< ...- Under worst ' and temp- I eVature the cables I i bend the towers I I about 2 ft toward I I the river. ie\ h'ite,'Side Cable^^r^ I e vTji-ijrp Land Fig. 17.—THE MAN- HATTAN BRIDGE HAS ITS SADDLES BOLTED TO THE TOPS OF THE TOWERS, WHICH BEND WHEN LOAD OR TEMPER- ATURE CHANGES THE POSITION OF THE CABLES. river. The sketch (Fig. 18) will help to make this clear. The result was that, on arriving at the opposite anchorage, the sheave had pulled Fig. 19.—ONE OF THE FOUR MAIN CABLES OF THE MANHATTAN BRIDGE COMPLETED AND TIED TEM- PORARILY, BUT NOT YET WRAPPED. VIEW NEAR ANCHORAGE SADDLES. A cable has a diameter of 20f inches, and is able to with- stand a strain of about 24,000 tons. a loop of wire across the river, giving in effect two cable wires. The closed end of this loop was now slipped off the sheave and dropped round a strand-shoe corresponding in position to the one at the other end of the wire. The four wires. There was a separate travelling rope, with motor, reels of wire, etc., for each cable, so that sixteen wires were laid at once. finished cable Traveling sheave Fig. 18.—DIAGRAM SHOWING ACTION OF TRAVELLING SHEAVE IN CABLE- Temporary sup- ports for strand SPINNING. PLACING TWO WIRES AT EACH OPERA- TION. The return side of the travelling rope carries a similar sheave, bringing wire over from the opposite anchorage, so that one trip of the travelling rope places four wires. by motor and gearing be/o* Under favourable conditions a round trip took about fifteen minutes, and over a hundred wires could be put in place in a single hour. Of course th© wires needed to be adjusted to exact position after being laid, and here the guide wire came into use. Men stationed at various points along the footbridge near the guide Adjusting , . . . , . the Wires, frames which supported the travelling rope worked in concert to make the adjustment. They laid the fresh, wire along the guide wire, pulled it up to the same posi- tion, and signalled from man to man until correct adjustment was secured. The slack