quarta-feira, 1 de abril de 2009

Tower Bridge's Steam Power

When Iwas living in London, during the 1970's, the East India's docks, Albert Docks and St Katherines, had just closed; the main port for London had been moved east to the mouth of the Thames and the large docklands area was a vacant lot.
I and many other small trades, moved into the docks and paid rent to the Port of London Authorities, the once famous Wapping police station and the Highway, with its 21 or more pubs, were now idle and without custom. The signs of the past greatness were still there, but it was a sad looking area and not even thieves saw value in staying, there was the odd petty thief, arms covered with watches and pockets full of antique rings, and it was not advisable to leave a radio visible in your car as that would be offered to the locals of the next pub along the Highway. Yet, with the Old Royal Mint at the end of the Highway, and the that facing the Tower of London, with its road running direct to Tower Bridge, on the South bank stood grand warehouses, still giving off the perfume of spices and teas from the orient; the power of the colonial empire was still visible, and some how Tower Bridge as the feeling of an entrance gate, when its draw bridge is lifted, it echoes the gate for the white castle tower on the other side, an evocative symbol, truly a not accidental feature in the architects mind.

When, in the 19th century, it became obvious that another bridge was needed across the River Thames (at the location of Tower Bridge) ship owners were incensed. How would their ships be able to reach the docks which lined the river from London Bridge down? A new bridge would ruin their business.
An Act of Parliament gave the dimensions for the bridge. It should have a central opening span 200 ft. wide and 135 ft. above Trinity high water and of 29 ft. when closed.
During the seven years it took to reach a decision fifty designs were submitted. They included a Duplex Bridge (from above it looked like a pair of wide-bridged spectacles) and three high level bridges. Many of them did not provide sufficient clearance for the tall ships.

It was Sir Horace Jones, the City of London Architect, who came up with the idea of a bascule-operated bridge. Even so, it wasn't immediately accepted. He enlisted the help of John Wolfe-Barry (youngest son of Sir Charles Barry, the architect of the Houses of Parliament) and in October 1884 tried again.
It took nineteen days of discussions before "Mr. Jones' flaps and wings" were granted Royal Assent and Parliament instructed the Corporation of London to build the bridge within four years - it took longer. nine years.

The new crossing point for the Thames river, London, conceived and built during the 1870s, 80s and 90s, Tower Bridge, encapsulates the struggle between the artist architect and his engineer, between a concern for history (the new bridge had to sit happily beside the ancient Tower of London) and the application of modern building technology. Tower Bridge is - in a very idiosyncratic way - a happy marriage of these potentially conflicting concerns, and perfectly encapsulates the topsy-turvy artistic tastes and values of late Victorian Britain. This movable bridge of the double-leaf bascule (drawbridge or sea-saw as the french word original implies) type that spans the River Thames between the Greater London boroughs of Tower Hamlets and Southwark. It is a distinct landmark that aesthetically complements the Tower of London, which it adjoins, built with the then Gothic style in prominence, and with vast amount of cast and forged steel, again the Victorian trade mark, and with the use of steam locomotion and power, also a Victorian symbol of progress and invention.

The bridge is at present undergoing restoration and repainting, 115 years after its opening by the then, Prince and Princess of Wales.

The opening on 30th June 1894 was spectacular with the Prince and Princess of Wales. Also in attendance were the Lord Mayor of London and the City Sheriffs with an escort of Life Guards.
The royal carried crossed and re-crossed the bridge to christen it. Eventually it came to a halt by a specially erected Royal Pavilion where the Prince of Wales (on behalf of Queen Victoria) opened the bridge. This was done by turning a specially designed silver cup mounted on a pedestal and linked to the hydraulic equipment. And he declared Tower Bridge open.
The bridge was completed in 1894 and provides an opening 250 feet (76 metres) wide. Its twin towers rise 200 feet (61 metres) above the Thames. Between the towers stretch a pair of glass-covered walkways that are popular among tourists. The walkways were originally designed to allow pedestrians to cross even while the bridge was raised, but they became hangouts for prostitutes and thieves and so were closed from 1909 to 1982.
The Tower Bridge centre road spans were operated by hydraulic pumps driven by steam until 1976, when electric motors were put into operation; the steam power system is still kept (in good repair) as a tourist display. Because of the reduction in shipping at the London Docklands, however, the leaves are now seldom raised.

The engine uses two cylinders and pistons, the steam enters the first high pressure cylinder, driving one pump and then leaves to enter the second low pressure cylinder driving a second pump. The whole boiler was kept under pressure 24 hours a day and night, producing a constant 80 lbs per square inch of pressure and a capacity of 300 horse power per engine. The engines also use six accumulators, to access as much power as possible for the driving of the two arms of the bridge.

These 100 tons accumulators where designed to store power when the bridge was not in use, the engines lifted great vertical shafts, inside the twin towers, and then these weighted shafts would be released for the bridge to be opened, providing the engines with a constant 100 tons of weight to balance the arms and allow the bridge to be opened by a set of eight lifting engines at a very fast, yet even rate.

Tower Bridge is the only moveable bridge on the River Thames, and is funded by an ancient trust - Bridge House Estates - which had been set up to manage London Bridge in the 11th Century. The trust keeps the bridge toll-free for road and river traffic, and is managed by the Corporation of London, who own and manage it. It is insured by Lloyd's of London on the shipping register as a ship, and for the first 23 years of its life, all staff were ex-sailors and servicemen.

The Tower of London, an imposing fortress was built around the White Tower (the massive keep at its heart) by William " the Conqueror" - the name White Tower dates from the thirteenth century, when Henry III, ordered the exterior to be whitewashed. Successive monarchs enlarged its defences and added more buildings. In its long history, the Tower of London has been a fortress, palace and prison, royal treasury and the kingdom's main arsenal. In 1100 the White Tower was host to the first of many hundreds of prisoners.

The evidence for the use of the Tower as a prison is plentiful, many of the towers have inscriptions carved by former inmates. Persons beheaded inside the Tower for treason include the following William Hastings, 1st Baron Hastings (1483), Anne Boleyn (1536), Margaret Pole, Countess of Salisbury (1541), Catherine Howard (1542), Jane Boleyn, Viscountess Rochford (1542), Lady Jane Grey (1554) and Robert Devereux, 2nd Earl of Essex (1601). Not surprisingly, the Tower of London has many "ghosts" and the reputation of being the place most frequently haunted in London

State prisoners were usually admitted through Traitors' Gate in St. Stephens Tower and executions took place on Tower Hill and inside the Tower on Tower Green. All the victims executed on Tower Green were buried nearby in the Chapel of St. Peter ad Vincula - consecrated during the reign of Henry I, burned down in 1512, re-built in 1520 and restored in 1876.

Although it is no longer occupied by the Royal Family, the Tower officially remains a royal residence and as such, maintains a permanent Guard. Two sentries are maintained during the hours that the Tower is open with one stationed outside the Jewel House and one outside the Queen's House.

Henry VIII was the last monarch to use the Tower as a royal residence but monarchs continued to go in procession from the Tower to Westminster for their coronation. This tradition continued until 1661 after the coronation of Charles II.

The tower is manned by the Yeomen Warders (known as Beefeaters), who act as tour guides, provide security and are something of a tourist attraction in their own right. Every evening, the warders participate in the Ceremony of the Keys, as the Tower is secured for the night.

The Tower is located at the eastern boundary of the City of London financial district, adjacent to the River Thames and Tower Bridge.

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