painstaking, methodical, working out every detail in advance. And once he had settled in his mind that he could do a thing, Roebling stuck to it. “Before entering upon any important work, he always demonstrated to the most minute detail its practicability…and when his own judgment was assured, no opposition, sarcasm, or pretended experience could divert him from consummating his designs, and in his own way.”
Roebling started his bridge in 1851 and it took him four years. He worked carefully, steadily, and there were no hair-raising escapades anyone would remember later. For Roebling the excitement of the work, the drama of building a bridge, were chiefly matters of the intellect and spirit. Physical dangers were part of the job, inevitably, but to be taken as they came, or, better still, avoided entirely if a safer way could be figured. The bridge he built was a thorough demonstration of theories he had been perfecting and preaching for a decade and more. “The only real difficulty of the task,” he wrote, “appears to be its novelty.”
Put in its simplest form, Roebling’s fundamental belief about suspension bridges was that the stiffer and heavier the roadway could be made, the more stable the bridge. To many this seemed contrary to common sense, since the weight of the roadway and its superstructure would seem to jeopardize those very elements that made a suspension bridge a suspension bridge—the cables.
Roebling was not the first to recognize the importance of a heavy, stiff roadway, just as he was not the first to use anchor stays or to spin his cables in place, all things he would be credited with initiating and reverently praised for by some of his more ardent admirers. James Finley had used stiffening beams and railings before Roebling was born and he knew the purpose they served. The scowling little Brunel, trudging about his bridges in a stovepipe hat, had directed that tension cables be attached to counteract the action of the wind. The French engineer Seguin wrote in 1824 that rigidity of the bridge floor was the surest means to prevent the “vacillations arising from moving loads of any considerable mass” and said the best way to achieve that rigidity was an arrangement of strong trusses.
There were others, too, including an English engineer named Rendel, who wrote the following before John A. Roebling had built a bridge:
In the anxiety to obtain a light roadway, mathematicians, and even practical engineers, had overlooked the fact that when lightness induced flexibility and consequently motion, the force of the momentum was brought into action and its amount defied calculation. The author has long been convinced of the importance of giving to the roadway of suspension bridges the greatest possible amount of stiffness…
But unlike most every builder of suspension bridges then, and some much later, Roebling not only understood these ideas, he applied them, his system of inclined, or diagonal, stays being an excellent case in point. “I have always insisted that a suspension bridge built without stays is planned without any regard to stiffness, and consequently is defective in a most important point.” And equally important, he did not apply some of the other theories in circulation at the time, many of them very bad theories, that were often taken seriously by the supposed experts. So if he cannot be honestly credited with originating all he preached, he at least was the one engineer who was practicing it properly.
In his original letter of proposal to the railroad men, Roebling had written that his bridge over the Niagara Gorge would stand up under a moving train because he would make it stiff enough to do so. He designed the two floors of the bridge and the open timber trusswork that was to bind them together as one enormous “hollow straight beam.” The timber would be well seasoned, well painted, and the upper floor, where the trains would cross, would be caulked and painted as
Roebling started his bridge in 1851 and it took him four years. He worked carefully, steadily, and there were no hair-raising escapades anyone would remember later. For Roebling the excitement of the work, the drama of building a bridge, were chiefly matters of the intellect and spirit. Physical dangers were part of the job, inevitably, but to be taken as they came, or, better still, avoided entirely if a safer way could be figured. The bridge he built was a thorough demonstration of theories he had been perfecting and preaching for a decade and more. “The only real difficulty of the task,” he wrote, “appears to be its novelty.”
Put in its simplest form, Roebling’s fundamental belief about suspension bridges was that the stiffer and heavier the roadway could be made, the more stable the bridge. To many this seemed contrary to common sense, since the weight of the roadway and its superstructure would seem to jeopardize those very elements that made a suspension bridge a suspension bridge—the cables.
Roebling was not the first to recognize the importance of a heavy, stiff roadway, just as he was not the first to use anchor stays or to spin his cables in place, all things he would be credited with initiating and reverently praised for by some of his more ardent admirers. James Finley had used stiffening beams and railings before Roebling was born and he knew the purpose they served. The scowling little Brunel, trudging about his bridges in a stovepipe hat, had directed that tension cables be attached to counteract the action of the wind. The French engineer Seguin wrote in 1824 that rigidity of the bridge floor was the surest means to prevent the “vacillations arising from moving loads of any considerable mass” and said the best way to achieve that rigidity was an arrangement of strong trusses.
There were others, too, including an English engineer named Rendel, who wrote the following before John A. Roebling had built a bridge:
In the anxiety to obtain a light roadway, mathematicians, and even practical engineers, had overlooked the fact that when lightness induced flexibility and consequently motion, the force of the momentum was brought into action and its amount defied calculation. The author has long been convinced of the importance of giving to the roadway of suspension bridges the greatest possible amount of stiffness…
But unlike most every builder of suspension bridges then, and some much later, Roebling not only understood these ideas, he applied them, his system of inclined, or diagonal, stays being an excellent case in point. “I have always insisted that a suspension bridge built without stays is planned without any regard to stiffness, and consequently is defective in a most important point.” And equally important, he did not apply some of the other theories in circulation at the time, many of them very bad theories, that were often taken seriously by the supposed experts. So if he cannot be honestly credited with originating all he preached, he at least was the one engineer who was practicing it properly.
In his original letter of proposal to the railroad men, Roebling had written that his bridge over the Niagara Gorge would stand up under a moving train because he would make it stiff enough to do so. He designed the two floors of the bridge and the open timber trusswork that was to bind them together as one enormous “hollow straight beam.” The timber would be well seasoned, well painted, and the upper floor, where the trains would cross, would be caulked and painted as
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