Safeguarding the Brooklyn Bridge

New Zealand Tablet, Volume XXXVI, Issue 22, 4 June 1908, Page 30

Safeguarding the Brooklyn Bridge

The recent' Quebec bridge disaster, which a Parliamentary (Jommission found was due to a fundamental defect in the des'igni, calls attention to the great care that is tak<en in tho inspection of the. Brooklyn Bridge, New York. No royal baby heir to a throne is nursed and coddled more carefully than this- great structure, bearing as it doies 'its amazing burden of traffic on< swaying cables high abo.e the Easl River. • Like an infant prince, its nurses note hour by hour its impatient squeaks ami groans, its peevish swaying from side to side, the rhythmic beating of its pulses. Medicines are quick ly applied for even trifling disorders. Its daily toilet may be compared with the morning routine of bath, talcum powder, and manicuring of infant experience. The minuteness of this nursing was shown the other •day by an experiment of one of the engineering corps. He 'stood at the middle of the bridge where' one of the great cables dips down to meet an iron, beam of the swinging superstructure. First he laid a sheet of paper on the beam. Then he fastened a strip of wood not unlike an office ruler, to a hanger just below the cable. The strip extended to the middle of the sheet of paper, and on the enid a short lead pencil, extending downward, rested with its tip on the drawing card. The appliance was like a seismograph for recording earthquakes or the arrow on a paper drum w'lth which the weather men noLe v'md variations. The pencil recorded on the paper the swinging of the great cable, backwards and forwards and from side to side. As the pencil traced its triangular course the- engineer noted the Brooklyn Rapid Transit trains passing on either side, noting the number of cars, their positions as the cable swung backward and forward, and whether they were crowded or empty. The acting engineer explained afterward this was onto of a series of observations taken periodically to safeguard the integrity of the bridge. In this swaying of tho cables lies the safety of the million® who cross the bridge. In fact, the central span is like a great hammock, as Jong as six blocks in upper Broadway, swaying slightly from side to side in the eight great cables witQi their wires long enough to reach from Brooklyn to Dublin. The wave motion causes the strain on the bridge, but it is resisted by the stiffening trusses. The surface Cars — enough every m.onth to form a continuous train from New York to Philadelphia— have little or no effect on. th© bridge. Neit-her have the streams of pedestrians, drays, automobiles. The plan for sliding platforms, now tabled for a time, would not alter the strain, as they would be merely a dead weight, instead of a shifting burden. As the pencil recorded the oscillations it was seen that the trams of cars were the real burden. If they should be run on one side of the bridge in one direction only, the engineer explained, the effect would be very much li'-:.e the sagging of a hammock when the hand is drawn heavily down one side. As the cars are constantly mo ing from both sides at once, however, the sagging, gives place to a wave-like motion. Nursing "the b r ig bridge means that day after day, whether in storms of snow or sleet, or in torrid heat, inspectors, bridgemen, and riggers climb like spiders to every part of the great structure, testing its 1,000,000 rivets, bolts, an/1 splices, inspecting the cables and trusses, scraping and painting the weather-beaten parts that show signs of rust or wear. Many of the cables, saddles, suspenders, bands, sockets, bolts, trunnions, trusses, floor beams, and stays are examined every day, Thais every part of the bridge is gone over at least once in every six months. Five inspectors are engaged in regular details. Every morning one of them walks over the spans, looking at every prominent feature and reDorting the results to the Department of Bridges. . Not a day passes that the joints and short suspenders near the middle, where experience has shown that breaks are likely to occur, are not insnected. - A man is employed every weekday oiling and cleaning the suspenders over the East River. Here the oscillation and shifting of the bridge, under the heavy train service, demands special attention. Another man, especially trained for the service, oil& and removes the dirt from the slip joints in the trusses of the centre of the river and land spans.