Cable Making of the East River Bridge

The stage of work through which the great East River Suspension Bridge is now passing may be considered that which includes the first permanent steps toward the formation of the superstructure or bridge proper. Hitherto piers and anchorages have been erected, the river spanned by a slender foot bridge, and the attendant temporary guys and braces, but until the last few days it has been impossible to say that any integral portion of the vast mass of suspended wire has reached a finished state. Now, however, two huge strands, respectively belonging to two huger cables, are permanently fixed in their great shoes pinned between the colossal eye bars of the anchorages, and fixed in the graceful curve with which they sweep over the river, their centers marking the lowest point of the majestic structure which they are to aid in supporting. In order to clear up any doubt in the reader's mind as to what the main cables and their office are—for to these the strands now finished belong—it may be well to explain that the bridge is to be held up by four immense wire ropes, or more strictly bundles of wire, for, contrary to general supposition, there is no twist in them. These cables pass from anchorage to anchorage, rising over the tops of the piers, two crossing the latter near the middle and one at each end. Their course can easily be followed on the engraving of the bridge as it will appear when finished in our next issue. It will be seen that the roadway which extends straight across the river from floor to floor of the great arches to the piers, and then from piers to anchorages, is suspended by smaller vertical cables of constantly varying length.

Each one of these mighty principal supporting ropes is [...] of nineteen strands, and each strand is made of 260 steel wires. The size of wire now used is number 7. Number 8 was first employed, but the larger size was preferred.

When these wires are laid side by side, they make a bundle 3 inches in thickness, and the weight and tension of the bundle extending as it does from anchorage to anchorage, appears in the shape of a pull of 40 tons at each end. So that each entire cable will exert a strain of just nineteen times that amount.

In this and the following article we propose to explain how these main cables are made, for although we shall describe simply the preliminary operation of strand making and securing, it will readily be seen that further operations involve but a series of repetitions.

It may be remembered that after our examination into the way the steel wire was made (the results of which we embodied in an article some months ago) we left the wire in large coils some five feet in diameter. Following these coils now to the Brooklyn anchorage—where is the spinneret whence the great cobweb is emerging thread by thread—we shall find them dipped in oil, dried in the air, dipped again and again until a moderately thick coat of hardened grease has changed their bright zinc lustre into a dirty yellow. Then they are carried up on the top of the anchorage, reeled off on large wooden drums, and from these last they are paid off as required. We have already explained how the first wires were got across the river. One of the first conveniences afterwards put in place was the carrier rope. This is simply an endless wire cable which starts from the Brooklyn anchorage, passes over the two piers in turn, then to the New York anchorage, on top of which are two horizontal pulleys, around which it leads, then back to Brooklyn, and finally after passing around an immense horizontal engine-driven drum the ends are joined. One part of this carrier rope carries wire for one inner main cable, the other part for the corresponding outer main cable. On each part is attached a traveler wheel, which is represented in Fig. 3. This is a light [...]