considerably. The flat curve, in which the wires are suspended, facilitates the tying together, and the separate attachment of the shoe gives ample working room for laying the wires into it. But the main advantage is derived from the fact that the tension in the wire is nearly doubled, amounting to about three quarters of the maximum tension to which it ever will be subjected in the finished bridge. This tests the wire to a certain extent, takes out all waves and bends, and leads to the easier detection of a defective wire or splice. It gives, therefore, to the engineer more or less assurance that all wires, worked in the cable, come up to the requirements and that the latter will obtain its calculated strength. The running out of the wires takes place from the Brooklyn anchorage, where all wire rings are received. A number of them, spliced together, are wound on wooden drums, which are large enough to contain about 12-14 wires of the length of the whole cable. The end of a wire, taken from the drum, is now temporarily fastened to the leg, and the loop, formed in this way, hung into a grooved wheel called "traveling sheave,” which is firmly attached to an endless rope stretched from anchorage to anchorage. The latter, called "traveling or working rope," passes at each anchorage around horizontally placed wheels which, connected with a steam engine, give motion to it. The traveling sheave with two wires are carried over by the rope. One wire, which is fastened to the leg appears to stand still, while the other, which unwinds from the drum, runs with twice the speed of the working rope. After their arrival at the New York anchorage, the wires are taken from the sheave and laid around the shoe in such a manner, that all standing wires occupy one side of it, and all running wires the other. These two wires are now regulated according to a "guide-wire " which previously has been suspended and adjusted to the desired deflection. The same operation is repeated 166 times, until all wires for one strand are stretched. The regulating is done by men standing on light platforms called. "cradles," which, supported by wire ropes, are erected at different places along the line of the cable. It is therefore necessary, that these cradles should be at such an elevation, that the wires of the strand hang about breast high to a man standing in them, so as to enable him to compare the relative deflections of the wires. In order to reach the cradles without difficulty and otherwise to facilitate general communication between all parts of the work, there is a narrow and light "footbridge," spanning the river and the spaces between towers and anchorages, which serves for all purposes. The wires of a strand are tied together with a wire lashing about every sixteen inches, and then lowered in their final position. A second strand is made in the same manand so on until with the nineteenth the cable is ready for wrapping. The strands occupy in the cable a certain ner, 930 -272 Cradle fulldrawn lines, Cradle and foot bridge Ropes final position of Cable in Centre span. NEW YORK |