Niagara Falls Suspension Bridge
Conception and building
Conception and building
In the middle of the 19th century, the hinterlands of the North American East Coast were opened up rapidly; colonists moved further inland, pushing back the wilderness and establishing settlements that grew into towns and cities. The growth of these centers of civilization was fueled by the increasing number of routes set up to facilitate trade among the settlements. Canadian entrepreneur and politician William Hamilton Merritt was a major contributor to the establishment of several trade routes in his country. His primary focus was on the lakes and the dredging of waterways to open up trade between the lake cities. He also showed interest in railroads, envisioning a network that connected cities on both sides of the United Statesanadian border from the Atlantic coast in the East to the new territories in the West. Merritt's dream would lead to the creation of a man-made structure, a railway suspension bridge, that spanned the Niagara River alongside the river's acclaimed natural feature, the Niagara Falls.
William Hamilton Merritt was the chief proponent for the Suspension Bridge, persevering to obtain charters for the bridge.
Merritt's vision for the Niagara Suspension Bridge was conceived at the Niagara River itself.[a] In the summer of 1844 while taking a picnic on the river shores, near what was then the town of Clifton, Merritt read a letter from his sons to his wife. The younger Merritts were touring Europe and visited the town of Fribourg, Switzerland. Amazed by the Freiburg Suspension Bridge, they wrote to their parents, describing the wonders of the bridge in eloquent terms. Their writing had a profound effect on their parents, and the elder Merritts wondered if such a suspension bridge could be built across the Niagara. Merritt was driven to realize that vision, and he approached the relevant authorities, including the Queen of England, for permission to start the construction of the suspension bridge. His efforts were rewarded in 1846; the state of New York and the government of Canada approved the charters to form the Niagara Falls International Bridge Company and the Niagara Falls Suspension Bridge Company, respectively.
In the years before the first bridge was built over the Niagara River, the river was crossed entirely by boats. Powered by steam engines, vessels ferried people and carriages across the raging river at calmer points of the water. One of these vessels was the Maid of the Mist, the first tourist boat to ply the waters of the Niagara River. Named after a local legend, the steamer began service in 1846. Launching from a point 2miles (3.2km) below the Horseshoe Falls, it chugged up to the base of the falls, offering a close-up view of the natural wonder to its passengers, before moving to the opposite shore. The site for the Suspension Bridge was half a mile (0.8km) from the Maid of the Mist's landings. The selection of the bridge site was based more on aesthetics than technical ease; it was the narrowest point of the gorge800feet (240m) across and 230feet (70m) deephat allowed a full view of the falls from the American side.
After the bridge companies were founded, they invited engineers to submit plans and cost estimates for a suspension bridge that carried a railway. The invitation was met with skepticism among the engineering community. At that time, there was not a suspension bridge that could allow a train to pass over it safely. While the Europeans were erecting suspension bridges by the hundreds, the Americans mostly ignored them out of safety concerns; in 1831 Sir Samuel Brown's Broughton Suspension Bridge in Britain had collapsed under the marching feet of a troop of soldiers, sending those on its deck into the River Irwell.[c] Furthermore, many American bridges had collapsed without experiencing weight and pressure equivalent to railroad traffic, and American engineers feared that any railway bridge would likely failspecially a suspension bridge.
Four engineers responded: Edward Serrell, Samuel Keefer, Charles Ellet, Jr., and John Augustus Roebling. All submitted designs for a suspension bridge. At the time of the bidding, Ellet and Roebling were acknowledged as masters of suspension bridge building in America. Roebling submitted two designs, a conservative single-deck suspension bridge and a double-decked version, both with meticulous calculations and drawings. Instead of relying solely on submissions, Charles Ellet, Jr. took a proactive approach. When he got wind of the project in 1845, he wrote to Charles B. Stuart, chief engineer of the Great Western Railway,[d] boldly proclaiming that he could build a bridge for any likely purpose across the Niagara. After the charters had been obtained, Ellet helped Stuart to sell the bridge companies' stock and offered to buy US$30,000[e] worth of stock himself. His efforts earned him the $190,000 bridge contract on November 9, 1847.
Charles Ellet, Jr.'s temporary bridge
For more details on the engineer, see Charles Ellet, Jr..
Charles Ellet, Jr., the first American-born civil engineer with European education in engineering, campaigned for suspension bridges in United States.
While growing up on a farm in Pennsylvania, Charles Ellet, Jr. scraped through odd jobs, but saved enough money to finance an education at the cole nationale des Ponts et Chausses in France. After attending four months of lectures, he toured Europe before returning to the United States as the only native-born American with European education in engineering. Ellet announced his ambitions to build suspension bridges in his country of birth by proposing to span the Potomac River with one. His proposal was ignored; few were willing to heed a young, inexperienced and impetuous engineer. To gain experience, Ellet started to work on railroads and canals, and later became the chief engineer on the James River and Kanawha Canal project. He further improved his reputation by contributing articles about suspension bridges to respected engineering journals, such as American Railroad Journal; eventually, Ellet built his first suspension bridge over the Schuylkill River, Pennsylvania, in 1842.
Ellet had the looks of an actor, which were complemented by his entertaining oratorical skills. He took advantage of these characteristics, and used showmanship and dramatics to market his proposals. These skills helped to win him attention and raise his profile both in the public and within the industry. However, his imperiousness also ruffled the feathers of people, which caused conflicts. Nonetheless, his capability to promote himself had won him the contracts for the Suspension Bridge and the later Wheeling Suspension Bridge; the Wheeling contract was won in July 1847 while Ellet's plan for the Niagara Suspension Bridge was still in its initial stages of construction. Ellet's initial design for the bridge at Niagara placed all forms of transportation on a single deck. The railway track was in the middle of the deck, sandwiched between carriageways and footpaths on the outer sides. Moreover, trains would not go over the bridge; their cars would be disconnected from the heavy locomotives and pulled across the bridge by horses, cables, or lighter 6-short-ton (5.4t) engines. Before the work could begin, Ellet faced the problem of all suspension bridge construction: getting a line across the gap.
Ellet's brainstorming sessions with his men raised several ideas that could enable a line to be suspended across the gorge; these included firing cannon balls with the line attached, towing it across the river with a steamer, and tying it to a rocket that would then be launched across the gorge. Ultimately the bridge engineer chose an idea inspired by Benjamin Franklin's experiment with a kite. It was similar to 15th century inventor Leonardo da Vinci's plan to span a gap. Ellet also took the opportunity to generate publicity for his project. Organizing a kite-flying contest, he offered $5[f] to any boy who flew a kite across the gorge and secured the kite string to the other side. Youths from nearby towns flocked in to participate. Unlike the other boys who flew their kites from the United States side of the gorge, 15-year-old Homan Walsh[g] crossed the river by a ferry upstream and walked to the Canadian side of the bridge site to launch his kite. He almost succeeded on his first attempt; his kite flew across but crashed just short of the shore. After resting several days at a friend's house, Walsh finally got his kite across the gorge and secured its line to a tree.
The basket, in which Charles Ellet crossed the Niagara Gorge, is on display at the Buffalo Historical Society.
Charles Ellet and his team tied a heavier line to the kite string and pulled the joined lines across. They pulled successive heavier and stronger lines across until the final bridge cable7/8inches (2.2cm) thickas hanging across the gorge. The cable was suspended between two wooden towers 40feet (12m) feet tall, and it was attached to an iron basket. Ellet planned to use this system as a basket ferry to shuttle workers and materials across the gorge, saving time that would otherwise have been spent on land and ferry travel. Through media coverage and word-of-mouth, many people knew of Ellet's efforts and flocked to the site to watch the construction. On March 13, 1848, the system was completed, and the team planned to test it by pulling the empty basket across. They hit a snag when the basket kept getting stuck halfway and could not move ahead. Pulling back the basket, Ellet decided to assure the watching crowd that the system was workable. He stepped into the basket, and it moved towards the opposite shore. When Ellet reached the problematic spot, he spotted the issue; the basket's rollers could not pass over a portion of the cable that had been accidentally flattened during the construction. He fixed the problem and proceeded to cross to the Canadian side and back, becoming the first person to cross the gorge. Although the bridge companies had prohibited Ellet from collecting tolls, he charged each person $1.00[h] for the chance to "observe first hand the engineering wonder of bridging the Niagara". On some days, the basket ferry conveyed up to 125 people across the gorge.
Continuing his construction, Ellet built two footbridges and joined them together to form an 8-foot (2.4m) wide suspension bridge. He intended to use this temporary bridge as a scaffold for the construction of the permanent railway bridge. On July 29, 1848, the bridge builder inaugurated the span in his typical manner; standing in his horse-buggy like a gladiator in his chariot, Ellet sped across the bridge, which had railings for only a third of its length at that time. His stunt garnered further publicity for the bridge, and the toll collected from the span proved lucrative; $5,000 was collected in less than a year since its official opening on August 1, 1848. Disputes arose between the bridge companies and Ellet over their shares of the money, and their relations turned bitter. The companies charged that Ellet was late in his schedule and withheld payment. Ellet retaliated by mounting cannons at the bridge to claim ownership over it. In the end the matter went to court. The bridge companies paid $10,000 to Charles Ellet, and he left the project to work full-time on the Wheeling Suspension Bridge.
The Niagara Suspension Bridge project was in hiatus for three years before the bridge companies engaged another renowned civil engineer, John Augustus Roebling, to complete it. The delay caused Roebling to miss out on the honor of building the first permanent bridge to span the Niagara; Serrell completed the Lewiston Suspension bridge in 1851. Roebling would, however, achieve other honors in building his Niagara Railway Suspension Bridge.
John Augustus Roebling's railway bridge
For more details on the engineer, see John A. Roebling.
Roebling's patent no. 4945 for the method to draw wires across gaps. This device was used to build the Suspension Bridge.
Born in Prussia (later a part of Germany), John Augustus Roebling obtained his first conditional engineering degree (Feldmesserprfung) at Erfurt in 1824. He attended two semesters of lessons at Berlin's Bauakademie and worked for the Prussian government, constructing military roads. Tired of the bureaucracy, he resigned his position and left for the United States in 1830, arriving with his brother in Philadelphia on August 6, 1831. Instead of continuing an engineering profession, he took up farming for a living. After five years he married a tailor's daughter, and had eight children with her over the next decade. Agrarian work was unsatisfactory to John Roebling, and in 1837, after the death of his brother and the birth of his first child, he returned to engineering.
Roebling first signed on as a surveyor for the Beaver River canal system, launching his career with a string of canal and railroad projects. Aside from writing articles in engineering journals, Roebling designed his own wire cables and started his own company to manufacture them; the John A. Roebling Company was the first wire rope manufacturer in the United States. Gradually gaining fame for his civil engineering, Roebling finally got to build suspension bridges. His first bridge was the Allegheny Suspension Aqueduct in Pittsburgh. The structure, completed in 1845, was the first suspension aqueduct in the world and the first large American suspension bridge that had multiple spans. Furthermore, it was the first suspension structure built with modern cable spinning techniquesoebling's own invention. Earlier bridge building techniques involved fabricating the main cables at a factory, transporting them to the bridge site, and then stretching the heavy cables over the gap to erect them over the bridge. Roebling, during his experiments with wire ropes, conceived and patented a new construction method for these main cables. A long linehe traveler ropeormed a loop around two horizontal wheels, one on each side of the gorge. A lightweight wheel, "the traveling wheel", was attached to this line, and a wire threaded around this wheel. Like a belt in a mechanical system, the traveler rope and its wheel moved across the gap as the horizontal wheels turned, pulling the wire along. The traveling wheel effectively hauled two lengths of the same wire (running above and under the traveling wheel) across the gap at a time. The lengths of wire were collected and bound at intervals to form thicker strands, which were later compressed together into the main cables. which supported themselves and later the proportional weight of the bridge as they were formed. The method became the standard for suspension bridge construction, and remained unchanged for many years. In the 20th century, suspension bridges were still built with this pulley winding system, albeit with more sophisticated equipment.
John Augustus Roebling built several prominent suspension bridges in the United States, earning him the esteem of the engineering community.
John Roebling was a contrasting character to Charles Ellet. Whereas Ellet embellished his proposals with fanciful words and deeds, Roebling presented papers filled with meticulous calculations and drawings. The elder engineer was stern and driven to achieve, taking a scientific approach to all interests. Rarely did he show emotions in his dealings, even to his closest associates. The man, however, dared to confront his detractors and make bold exaltations about his work. He openly called European suspension bridgesncluding American suspension bridges built with European techniqueseak, and occasionally sniped at Ellet's and Stephenson's works. He announced that his Brooklyn Bridge, when completed, "will not only be the greatest bridge in existence, but it will be the greatest engineering work of this continent, and of the age." Roebling's history with Ellet started before the bidding for the Niagara Suspension Bridge, early in their careers. During the bidding for the Schuylkill Suspension Bridge project, Ellet had written a proposal that was published in the American Railroad Journal. Mistakenly believing Ellet had won the contract, Roebling wrote to offer his congratulations and requested to be Ellet's assistant. He received a formal reply without any reference to his request, and his subsequent letter was ignored. When Roebling learned that a contractor had won the bid, he successfully applied to be the contractor's chief engineer. Ellet, however, persisted with his tactics and snatched the project away from the contractor; he promoted himself to the bridge company and offered to accept land instead of cash as payment. From then on, Ellet and Roebling became rivals, vying with each other for suspension bridge projects in North America. Roebling learned from their rivalry. His losses to Ellet showed him that he needed to promote himself and gain backers to effectively secure the contracts he desired.
When Roebling was called to the Niagara Suspension Bridge project in 1851, he had six suspension structures to his name. He found Ellet's final plan to be impractical; the bridge would have been too heavy and expensive. Roebling had another design in mind: the double-deck bridge he had proposed earlier during the bidding. The lower deck, level with the edge of the chasm, would convey passengers and carriages, and the upper deck, 18feet (5.5m) above, would allow fully laden trains to continue their journeys non-stop, albeit at a speed of 5miles per hour (8.0km/h). Roebling reasoned that the decks and sufficient trusses would form a rigid tube, making the bridge stiffer than a normal suspension bridge. The theory was similar to that of the tubular bridge but implemented at a lower cost. The engineering community was critical of Roebling's project. Robert Stephenson, builder of the tubular Britannia Bridge, was among those short-listed to complete the Niagara Suspension Bridge before Roebling's selection. Stephenson had submitted a design for a tubular bridge, and in 1859 he built a large and expensive tubular bridge for the Grand Trunk Railway at Montreal, Quebec. The bridge builder then said in derision of Roebling's suspension railway, "If your bridge succeeds, mine is a magnificent blunder."
In the face of criticism, Roebling completed the project in four years, using Ellet's bridge as scaffolding. The railway deck was stress-tested by the crossing of the 23-short-ton (21t) steam engine London at a speed of 8miles per hour (13km/h) on March 8, 1855. Ten days later the upper deck of the bridge was officially opened; the lower deck had been opened to the public a year earlier. As the first commercial passenger train t
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