Tower Bridge is one of the most famous tourist sights in the world, an icon of London, and a symbol of the ingenuity of Victorian engineering. The Tower Bridge Exhibition lets you discover the story of the bridge and how it was built, through interactive displays and videos about the landmark and its place in the history of the river Thames.
The history of the bridge started in 1876, when the Corporation of London invited amateur and professional engineers to submit designs for a low-level river crossing with mechanical openings. The bridge had to provide clearance of 43.5m for tall-masted sailing ships.
Sir Horace Jones, the architect and surveyor to the corporation, put forward a design of his own. The plan was for a bascule – French for seesaw – bridge, based on examples of lifting spans he had seen on the Continent. His design featured a road in two parts that opened in the middle, each part pulled up like a drawbridge to allow ships to enter.
An initial plan, which featured an arch, was rejected by the corporation. However, Jones sought out architect John Wolfe Barry to improve his design. The new plan, a bascule bridge with two Gothic towers and upper pedestrian walkways, was formally adopted with the passing of the Tower Bridge Act of 1885.
The bridge took eight years and £1,184,000 to build – far more than was originally estimated by Barry. During construction there were 29 serious injuries and 10 men died, which isn’t a surprise when you consider they were working at heights of more than 30m with no safety netting.
The steel bascules were operated by hydraulics using steam to power pumping engines. Six accumulators were used to store the energy, so it was readily available to lift the bascules. The bridge moves on a pivot with a weight of
382 tonnes of lead and iron, counterbalancing the longer length of the other end. The counterweights permit the bascules to be raised to an opening angle of 86°, although typical openings average 20-50°.
In 1972 the steam-driven power engines which had served the bridge for 80 years without fail were replaced by a new electric oil-hydraulic system. Five years later electric controls, which raised the bascules at the push of a button, were installed and the bridge could be run with a staff of a dozen.
In 1982 a new chapter in the life of Tower Bridge began when the upper walkways, encased in glass-reinforced plastic, were reopened to the public for the first time since 1910. The glass floor measures 11m long and 1.8m wide and comprises panels weighing 530kg each.
The fitting of the floor was part of an extensive renovation programme that also saw an underground exhibition centre created to enable visitors to see the Victorian machinery that has run the bridge so reliably. Videos and diagrams are on hand to explain how it all worked.
Entrance to Tower Bridge costs £9 for adults, although discounted tickets can be bought online. This includes access to the glass walkways, an exhibition on bridges, and the engine room. Special guided tours are also available. The bridge is raised about 1,000 times each year – opening times are available online.
For more details, see: www.towerbridge.org.uk
FIVE THINGS TO SEE
1. Engine room: Discover the huge and beautifully maintained steam engines, furnaces and accumulators that were once used to power the raising of the bridge’s bascules.
2. Exhibition on bridges: Discover the bridge’s colourful history from Victorian times to the present day through films, animations and interactive displays in the towers.
3. Glass walkways: These offer visitors a never-seen-before view of London life, from 42m above the Thames. Look down on buses whizzing over the bridge – and see the bascules being raised beneath you.
4. The bridge being raised: Time your visit to coincide with the raising of the bridge to let river traffic through. It normally happens three times a day and takes two and a half minutes to fully open and close.
5. HMS Belfast: A stone’s throw away from Tower Bridge lies this museum ship, originally a Royal Navy light cruiser launched in 1938, and now permanently moored on the river Thames.