Falkirk Wheel
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The Falkirk Wheel (Scottish Gaelic: Cuibhle na h-Eaglaise Brice) is a rotating boat lift in Tamfourhill, Falkirk, in central Scotland, connecting the Forth and Clyde Canal with the Union Canal. It opened in 2002 as part of the Millennium Link project, reconnecting the two canals for the first time since the 1930s.
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 to create a dramatic 21st-century landmark structure to reconnect the canals, rather than simply recreating the historic lock flight.
The wheel raises boats by Template:Convert, but the Union Canal is still Template:Convert 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 working boat lifts in the United Kingdom, the other being the Anderton Boat Lift.
Operation
Structure
The wheel has an overall diameter of Template:Convert and consists of two opposing arms extending Template:Convert beyond the central axle and taking the shape of a Celtic-inspired double-headed axe.<ref>Template:Cite journal</ref><ref name=i29>Template:Harvnb</ref><ref name=asme>Template:Cite web</ref> Two sets of these axe-shaped arms are connected to a Template:Convert diameter central axle of length Template:Convert.<ref>Template:Harvnb</ref> Two diametrically opposed water-filled caissons, each with a capacity of Template:Convert, are fitted between the ends of the arms.<ref name=qqf>Template:Cite web</ref>
The caissons, or gondolas, always carry a combined weight of Template:Convert of water and boats, with the gondolas themselves each weighing Template:Convert.<ref name=infv/> 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.<ref name=qqf/><ref name=asme/> Site-wide computer control system maintain the water levels on each side to within a difference of Template:Convert with water level sensors, automated sluices and pumps.<ref name=infv/><ref name=bacsol>Template:Cite web</ref> It takes Template:Convert to power ten hydraulic motors, which consume Template:Convert per half-turn, roughly the same as boiling eight kettles of water.<ref name=infv/>
Each of the two caissons is Template:Convert wide and Template:Convert long. Each can hold up to four Template:Convert canal boats.<ref name=et>Template:Cite web</ref> The wheel raises or lowers boats a total of Template:Convert, and two subsequent locks raise or lower boats another Template:Convert.<ref>Template:Cite book</ref><ref>Template:Cite web</ref>
Watertight doors
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 hinged doors were chosen.<ref name=door>Template:Cite web</ref> The doors are raised from a recess in the base of the caisson and powered by a hydraulic lance when docked.<ref name=door/>
After the wheel arms are moved into the vertical position, the locking mechanisms are activated. These include securing pins that are protruded into the caisson bases, and hydraulic clamps that are raised to hold the caissons in place. Additionally, a set of larger securing pins at the lower structure is used to hold the wheel. Although the door of the upper caisson and the door that holds the water at the upper aqueduct are aligned, there is a gap between them. The upper aqueduct door has a U-shape watertight frame which can be extended to push against the caisson door to seal the gap. The water is pumped into the gap to fill to the water level. Once the water in the gap is equalized, the door on the aqueduct side is lowered, followed by the door on the caisson side, allowing the boat to pass. On the reverse direction, when the boat is in the caisson, the caisson door is raised, followed by the upper aqueduct door. The water is pumped out of the gap. Then the U-shape watertight seal is recessed back closer to the upper aqueduct door. Finally, the locking mechanisms are removed before the wheel is turned. This process is similar for the door at the lower canal basin as well.<ref>Template:Cite web</ref>
- Doors, locking mechanisms, and seals
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Upper aqueduct door with U-shape seal and pumping system
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Locking mechanisms include securing pin at the top and hydraulic clamp at the bottom
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Securing pin and clamp receptors on a caisson (1 and 2), and a wheel securing pin receptor (3)
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Left to right: caisson door (behind the rail) aligned with basin door but with a gap, u-shape seal extended, water filled, and doors lowered
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The doors being lowered at the lower canal basin
Engine room
The area housing the machinery to drive the wheel is located in the final pillar of the aqueduct, and contains seven chambers connected by ladders.<ref name=tt/> Access is by a door located at ground level or an entrance halfway up the tower, with a gantry crane to facilitate the installation of equipment.<ref name=tt/>
The ground floor houses the transformers for powering the wheel. When the wheel was flooded by vandals in April 2002, this room was filled to within Template:Convert of the 11Template:NbspkV busbars.<ref name=tt/> On the first floor is a standby generator and switchgear should the mains supply to the wheel fail.<ref name=tt/> The second floor houses a pair of hydraulic pumps that drive the hydraulic motors in the chamber above.<ref name=tt/> Power is supplied directly to the axle with 10 hydraulic motors, which also double as brakes. Connected to each motor is a 100:1 gear system to reduce the rotation speed.<ref name="tt" />
Mechanism
The caissons are required to turn with the wheel in order to remain level. Whilst the weight of the caissons on the bearings is generally sufficient to rotate them, a gearing mechanism using three large identically sized gears connected by two smaller ones ensures that they turn at precisely the correct speed and remain correctly balanced.<ref name=hdiw>Template:Cite web</ref>
Each end of each caisson is supported on small wheels, which run on rails on the inside face of the Template:Convert diameter holes at the ends of the arms.<ref name=hdiw/> The rotation is controlled by a train of gears: an alternating pattern of three Template:Convert diameter ring gears and two smaller idler gears, all with external teeth, as shown in the picture.<ref name=hdiw/> The large central gear is fitted loosely over the axle at its machine-room end and fixed in place to prevent it from rotating.<ref name=tt>Template:Cite web</ref><ref name=hdiw/> The two smaller gears are fixed to each of the arms of the wheel at its machine-room end. When the motors rotate the central axle, the arms swing and the small gears engage the central gear, which results in the smaller gears rotating at a higher speed than the wheel but in the same direction. The smaller gears engage the large ring gears at the end of the caissons, driving them at the same speed as the wheel but in the opposite direction. This cancels the rotation due to the arms and keeps the caissons stable and perfectly level.<ref name=hdiw/>
Docking pit
The docking pit is a drydock-like port isolated from the lower canal basin by watertight gates and kept dry by water pumps.<ref name=ew/> When the wheel stops with its arms in the vertical position it is possible for boats to enter and exit the lower caisson when the gates are open without flooding the docking pit. The space below the caisson is empty.<ref name=ew/><ref name=et/>
Without the docking pit, the caissons and extremities of the arms of the wheel would be immersed in water at the lower canal basin each time the wheel rotated.<ref name=ew/> The buoyancy of the lower caisson would make it more difficult to turn the wheel.<ref name=ew/>
Visitor centre
A visitor centre is located on the east side of the lower basin.<ref name=p1890/> Boat trips on the wheel depart approximately once an hour.<ref>Template:Cite web</ref> Since the wheel opened, around 5.5 million people have visited<ref>Template:Cite web</ref> and 1.3 million have taken a boat trip, with around 400,000 people visiting the wheel annually.<ref>Template:Cite web</ref><ref>Template:Cite news</ref>
See also
- Anderton boat lift
- Canals of the United Kingdom
- Forth and Clyde Canal Pathway
- Lifts on the old Canal du Centre
- List of boat lifts
- Peterborough Lift Lock
- Strépy-Thieu boat lift
- The Helix (Falkirk)
References
Citations
Sources
External links
- Template:Official website
- "The Hidden Engineering Behind the Falkirk Wheel", Practical Engineering. Video with Grady Hillhouse.
- Pages with broken file links
- Boat lifts
- Transport infrastructure completed in 2002
- Buildings and structures in Falkirk
- Buildings and structures celebrating the 3rd millennium
- Locks of Scotland
- Tourist attractions in Falkirk (council area)
- Scottish Canals
- 2002 establishments in Scotland
- Articles containing video clips