The Falkirk Wheel
A unique engineering achievement
Scotland's Falkirk Wheel is the only rotating boat lift anywhere in the world. Since its opening in 2004, it has served as the centrepiece of the £79.2m Waterway Revival scheme, an ambitious effort to make the country navigable once more by joining two long-separated waterways, the Kinnaird Canal and the Strathavon Canal.
What made the undertaking so difficult was the gap in height between the two: the Kinnaird Canal lies some 32 metres beneath the Strathavon. In earlier times a chain of nine locks — walled stretches of canal whose water level can be raised or lowered — had carried vessels between them, descending over 1.8 km near the town of Falkirk. Once these were taken out of service in 1928, the link between the waterways was lost. On launching the scheme in 1996, the waterway authority was determined to produce a bold modern landmark, one that would at once mark the new century and stand as a lasting emblem of the region's economic renewal.
Proposals of every kind poured in, from tilting basins and rolling drums to enormous seesaws and monorails suspended overhead. What finally won out was the design for the colossal revolving steel lift now known as the Falkirk Wheel. Those behind it have traced its distinctive form to a blend of natural and manufactured origins — a Celtic brooch above all, though also the curved blade of a scythe and the slowly unfurling frond of a fern.
Every component of the Wheel was fabricated and test-fitted, much like the pieces of an enormous construction kit, at Rennox Engineering's yard in Lanarkshire, roughly 350 km from the site. Workers there brought together some 1,400 tonnes of steel, aligning each part to within 8 mm so that the finished structure would fit flawlessly. It was then taken apart in the summer of 2003 and carried to Falkirk on forty lorries, where it was put back together on the ground and, in six large sections, hoisted into place by crane. Because the Wheel has to cope with huge and constantly shifting loads as it turns, its sections were fastened with bolts rather than welds; more than 50,000 holes were matched to their bolts, each one tightened by hand.
Rising from a fixed central spine are two opposing pairs of axe-shaped arms, set roughly 22 metres apart, and slung between their tips are two water-filled 'gondolas', each holding 300,000 litres. Whether loaded or empty, a gondola weighs exactly the same — a result of Archimedes' principle, under which a floating body pushes aside a volume of water equal to its own weight. The instant a boat floats in, the water forced out of the gondola matches that boat in weight. Kept in this way in perfect balance, the Wheel's great bulk swings through 180° in about six minutes on strikingly little power: one rotation uses roughly 1.2 kilowatt-hours, no more than is needed to boil six household kettles.
To be raised, a boat first moves into the basin, which sits at the level of the Kinnaird Canal, and floats on into the Wheel's lower gondola. Two hydraulic steel seals then rise to shut the gondola off from the basin water, after which whatever is trapped between them is drained away by pump. Holding the arms motionless during docking is a hydraulic brake; once this is let off, the Wheel is free to swing. The turning is driven from the central machine room, where ten hydraulic motors set the main shaft in motion and, through it, the outer arms, which come round at a tenth of a revolution each minute. To stop the gondolas from tipping as all this happens, a simple arrangement of gears is used: a set of large gears circles a fixed central gear of equal size, with smaller gears between them spinning the other way, so each gondola stays level throughout. The boat, on reaching the top, glides straight off onto an aqueduct perched 22 metres above the basin.
The final 10 metres up to the Strathavon Canal are managed by a pair of locks, since the Wheel itself could not be built to bridge the whole 32-metre difference. What stood in the way was the Callendar earthworks, which dated from the Iron Age and had to be left undisturbed. Boats accordingly pass beneath them through a tunnel, climb the locks, and come out at last on the upper canal.
Kéo chỉnh
Question 1 - 6
Choose TRUE/FALSE/NOT GIVEN
1.
The two waterways had been linked to each other at some point before the Wheel existed.
True
False
Not given
2.
Only a handful of proposals were put forward for reconnecting the canals.
True
False
Not given
3.
The steel used in the Wheel was produced specially for this project.
True
False
Not given
4.
The sections of the Wheel were welded together to give it greater strength.
True
False
Not given
5.
A gondola's weight is unaffected by whether or not it is carrying a boat.
True
False
Not given
6.
The Wheel turns more slowly today than it did when it first opened.
True
False
Not given