The Falkirk Wheel is a rotating boat lift in Scotland, connecting the Forth and Clyde Canal with the Union Canal. The lift, named after the nearby town of Falkirk in central Scotland, opened in 2002. It reconnects the two canals for the first time since the 1930s as part of the Millennium Link project. The plan to regenerate central Scotland's canals and reconnect Glasgow with Edinburgh was led by British Waterways with support and funding from seven local authorities, the Scottish Enterprise Network, the European Regional Development Fund, and the Millennium Commission. Planners decided early on to create a dramatic 21st-century landmark structure to reconnect the canals, instead of simply recreating the historic lock flight. The wheel raises boats by 24 metres (79 ft), but the Union Canal is still 11 metres (36 ft) higher than the aqueduct which meets the wheel. Boats must also pass through a pair of locks between the top of the wheel and the Union Canal. The Falkirk Wheel is the only rotating boat lift of its kind in the world, and one of two boat lifts in the United Kingdom, the other being the Anderton boat lift.
The wheel has an overall diameter of 35 metres (115 ft) and consists of two opposing arms extending 15 metres beyond the central axle and taking the shape of a Celtic-inspired, double-headed axe.Two sets of these axe-shaped arms are connected to a 3.8-metre (12 ft) diameter central axle of length 28 metres (92 ft). Two diametrically opposed water-filled caissons, each with a capacity of 250,000 litres (55,000 imp gal; 66,000 US gal), are fitted between the ends of the arms.
The caissons or gondolas always carry a combined weight of 500 tonnes (490 long tons; 550 short tons) of water and boats, with the gondolas themselves each weighing 50 tonnes (49 long tons; 55 short tons). Care is taken to maintain the water levels on each side, thus balancing the weight on each arm. According to Archimedes' principle, floating objects displace their own weight in water, so when the boat enters, the amount of water leaving the caisson weighs exactly the same as the boat. This is achieved by maintaining the water levels on each side to within ±37 millimetres (1.5 in) using a site-wide computer control system comprising water level sensors, automated sluices and pumps. It takes just 22.5 kilowatts (30.2 hp) to power ten hydraulic motors, which consume just 1.5 kilowatt-hours (5.4 MJ) per half-turn, roughly the same as boiling eight kettles of water.
The two caissons are 6.5 metres (21 ft) wide, and can hold up to four 20-metre-long (66 ft) canal boats. Watertight doors at each end match doors located on the upper structure and lower dock pit. Due to space concerns, where a normal hinged door would dramatically reduce the useful length of the caisson, vertically rising doors were chosen. The doors are raised from a recess in the base of the caisson and powered by a hydraulic lance when docked. (The Falkirk Wheel)