Engineering Wonders of the World
Volume I

TRANSPORTER BRIDGES. 295 Fig. 11.—THE RUNCORN TRANSPORTER BRIDGE, THE LARGEST OF ITS KIND. IT HAS A SPAN OF 1,000 FEET, AND CROSSES THE MERSEY AND THE MANCHESTER SHIP CANAL. There are only two cables, one over each pair of towers, and instead of hanging vertically, as in the other bridges, they are “ cradled ” -—that is to say, they are _ drawn nearer to each other Cables. at the centre of the bridge than they are at the towers. The main cable and backstays leading to the anchorages are all in one piece, and consist of nineteen steel ropes or strands bound together, each rope being built up of 127 wires 46 inch in diameter. Each cable consists of 2,413 wires, and weighs about 130 tons. At the points where they pass over the towers the cables rest upon large cast-iron saddles, supported upon rollers to permit small movements. A side view of the actual saddle is shown in Fig. 14. The top of the saddle is I grooved to receive the cable. As the backstay leaves the tower at a sharper angle than does the main cable, the tendency of a load on the central span is to move the saddle riverwards. This tendency is overcome by clamping the cable to the saddle with four plates and twenty- four bolts. Owing to gross carelessness in not seeing that these bolts were tight, an accident happened the day after the bridge was opened, when it was found that all the nuts were quite loose, and had allowed the saddle to slip in consequence. The method of attaching the nineteen ropes to the anchorage is shown in Fig. 15, where the ends are to be seen fixed to screwed adjustable couplings passing through steel forged crossheads, thence by links to the anchorage. All the nineteen ropes are gathered together at a point about 60 feet