Tower Bridge—Gateway to London
BY AWAKE! WRITER IN BRITAIN
FOREIGNERS who have never traveled to England recognize it. Annually thousands of tourists visit it. Every day, London residents cross it, perhaps without a glance or a thought of its origins. Tower Bridge is one of London’s best-known landmarks.
Not to be confused with its neighbor London Bridge, Tower Bridge is associated with the nearby Tower of London. Back in 1872, England’s Parliament considered a bill to authorize the building of a bridge over the Thames. Despite objections from the Tower’s governor, Parliament decided to pursue this idea of another crossing, provided its design harmonized with the style of the Tower. The present-day Tower Bridge developed from this official proposal.
During the 18th and 19th centuries, numerous bridges connected the banks of the Thames, the most famous being Old London Bridge. By 1750 that bridge straddled the river on shaky foundations and was a bottleneck for crossing traffic. Beneath it ships from around the world jostled for position in the crowded port. Back then, the shipping was so thick that it was said one could walk for many a mile across the adjoining decks of docked vessels.
At the instigation of the Corporation of London, city architect Horace Jones proposed a Gothic-style drawbridge to be built downstream from London Bridge. It would provide free passage for ships heading westward up the Thames to the docks. This design incorporated what many considered to be a novel feature.
Jones had traveled widely, and the small drawbridges that spanned canals in the Netherlands gave him the idea of a counter-balancing bascule bridge. Designed with fashionable methods of construction using steel frame with masonry cladding, the now famous shape of Tower Bridge grew from his team’s drawing board.
Tower Bridge has two main towers connected at a high level by two walkways 110 feet [34 m] above the roadway and some 139 feet [42 m] above the river’s average high-water mark. The roadways leading from each riverbank terminate in a counterweighted bascule, or seesaw. These giant leaves of the bridge weigh some 1,200 tons each and swing apart and upward to an angle of 86 degrees. Ships up to a tonnage of 10,000 can pass safely underneath.
Power for the Bascules
It was hydraulic power that lifted the bridge’s bascules, moved the passenger elevators from road level to the walkways, and even worked the signaling. Yes, water was used in the operation of this bridge! And it provided power in abundance—twice as much as was needed.
Installed under the bridge’s southern approach, four coal-fired boilers, which generated steam at a pressure of between 75 and 80 pounds per square inch [5-6 kg/cm2], drove two massive pumps. These, in turn, delivered water at 850 pounds of pressure per square inch [60 kg/cm2]. To maintain the energy needed to lift the bascules, six large accumulators stored the pressurized water. These fed a total of eight engines that operated the bascules. Once the power was switched on, the counterweighted bascules swung upward on their 21-inch [50 cm] supports. It took only a minute to raise them to their full height.
A Visit to the Modern Tower Bridge
Nowadays electricity has replaced steam power. But, as in former years, when Tower Bridge opens, road traffic comes to a standstill. Pedestrians, tourists, and other visitors marvel at the workings of the bridge.
A warning alarm sounds, barriers come down to close off the roadways, the last vehicle completes its crossing, and the bridge controllers signal all is clear. Noiselessly the bascules’ four connecting bolts open and the bascule leaves swing skyward. Then attention turns to the river. Whether it is a tugboat, a pleasure-cruiser, or a sailing ship, all eyes follow the craft’s passage. Minutes later the signals change. Down swing the bascules, and up go the road barriers. Cyclists dart in front of waiting vehicles to cross first. Seconds later, Tower Bridge is still until its next wake-up call.
The interested visitor does more than just watch this oft-repeated train of events. He, along with others, takes the elevator ride up the north tower to admire the details of the bridge’s history, carefully displayed with an animatronic model in the “Tower Bridge Experience” exhibition. The engineering feats and the lavish opening ceremony are depicted on artists’ canvasses, and grainy, sepia-colored photographs and display panels bring the marvel of Tower Bridge to light.
The high-level walkways allow a visitor to enjoy splendid views of London’s skyline. Westward, St. Paul’s Cathedral and the bank buildings of the financial district come into view and, in the distance, the Post Office tower. Eastward, one would expect to see the docks, but these have migrated far downstream from the modern metropolis. Instead, Docklands, an area of urban renewal, is startling with its innovative building design. Spectacular, enthralling, interest-arousing—yes, all of these terms aptly describe the view from this famous London landmark.
When you visit London, why not take an in-depth look at this historic construction? Your visit will leave you with a lasting impression of a remarkable engineering feat.
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One of two steam-driven pumps that once powered the engines
Copyright Tower Bridge Exhibition
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The two bascules of the bridge are raised to their full height in less than a minute
©Alan Copson/Agency Jon Arnold Images/age fotostock
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© Brian Lawrence/SuperStock