The Clyde and Forth Canal and the Union Canal in central Scotland were major commercial arteries from the time of their construction in the late 1780s up until the 1930s, when economic competition from motor vehicles overtook ferry transportation.
For the next 75 years, these canals fell onto disuse and disrepair -- the 11 locks that originally compensated for their 24m height difference were paved over and built upon. However, in the early 21st century, Scottish authorities hatched a plan to refurbish the canals and feature a landmark structure that would reconnect the waterways.
The result? The Falkirk Wheel, the world's only rotational boat lift.
Lock-style boat lifts, like those at the Panama Canal, look like a series of steps. When a boat enters the first lock, it fills with water until it reaches the next level, where the boat moves forward to the next lock and the process repeats. The Falkirk Wheel, meanwhile operates using Archimedes Principle to balance twin gondolas, known as caissons, as they make the eight-story vertical journey. The structure is 35m wide overall and 35m tall -- the equivalent of eight double-decker buses stacked atop one another. Two opposing caissons, each holding the equivalent of 363,400L, sit roughly 2m apart on either side of the central axle. 4m wide slewing bearings keep the gondolas level as they rotate.
The structure required more than 1088 tonnes of steel to complete and rests on piled concrete foundations.
Altogether, the water and gondolas weighs about 544 tonnes. That's a lot of weight moving around -- enough to stress and eventually fatigue normal welded seams. To compensate, the wheel's construction called for 15,000 bolts -- each one hand-tightened -- with to a tolerance of just 10mm. However, despite its mass, the wheel can lift a gondola in just five and a half minutes by employing 10 hydraulic motors powered by a single 30hp electric motor that draws the same amount of power (1.5 kilowatt-hours in four minutes) as the act of boiling eight kettles of water.
Even the price tag for this impressive structure is surprisingly svelte, costing a mere £17.5 million to design and construct.
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