The rotating mechanism on the wheel lifts boats from one canal to another
Joanna Harrison on how The Falkirk Wheel became the engineering monument that it is.
"Until 1933, 11 locks linked the Union Canal with the Forth and Clyde Canal, 34 metres below.
Weary travellers had a day's heavy work opening and closing 44 lock gates to complete the journey between the waterways.
Declining commercial use meant they were maintained for safety reasons and as land drains.
In the 1970s renewed interest in the potential of the canals for boating leading to the largest canal restoration scheme, The Millennium Link, unveiled by Queen Elizabeth II in May 2002.
21st Century engineering
The revival of the two canals as part of the project created a new canal connection, whose design is a fine example of 21st Century engineering.
The site chosen was a steep sloping field on the outskirts of Falkirk.
The natural amphitheatre was home to a tar works, lying 3km from where the original locks lie buried.
The world's first rotating boatlift, The Falkirk Wheel, is an internationally recognised landmark.
Weight and grace
Water levels at the wheel are monitored by computer systems
The Falkirk Wheel is a deceptive blend of weight and grace.
At 35 metres high and 27 metres long, it is the height of eight double-decker buses.
Weighing 1,800 tonnes in total, the Wheel itself is 1,200 tonnes of steel.
Each of the 50 tonne gondolas transfer 250 tonnes of boats and water.
The Wheel is capable of lifting loads equivalent to the weight of 100 African elephants.
Despite such tonnage, The Falkirk Wheel can take a gondola with boats the 25 m vertical distance between the Union and Forth and Clyde canals using the power used to boil eight kettles.
Boat journeys take 15 minutes.
The half turn between the two canal heights takes five minutes.
How is the Wheel so smooth and energy efficient?
The design employs Archimedes Principle which means that as a boat enters the gondola it displaces exactly its own weight in water.
Differing water depths could create an imbalance.
Water levels in the aqueduct and lower basin are monitored by sensors, valves and hidden bypass pipes in the aqueduct and lower basin.
Computer software can even predict if tolerances are likely to be exceeded and take early preventative action.
The original design was based on a ferris wheel with four hanging gondolas
The unusual design of The Falkirk Wheel has been described using Scottish and marine architectural terms including a Celtic inspired double-headed axe, the spine of a fish, ribcage of a whale and the vast turning propellers of a Clydebank-built ship.
The original concept of a wheel to act as a boatlift wasn't new.
Dating from 19th Century Europe it was first seriously considered by British Waterways Scotland as a solution for Falkirk in 1994.
Dundee architects, Nicoll Russell Studios presented a ferris wheel type design with four hanging gondolas. This was used to secure Millennium Commission Funding. A lift was added which could raise and lower boats.
Giant brick set
Constructed like a giant brick set at Butterley Engineering Steelworks in Derbyshire, the structure was then dismantled and transported on 35 lorry loads to Falkirk.
A team painstakingly assembled the 1,200 tonne structure to an accuracy of just 10mm to ensure a perfect final fit with the 25m long axle section aligned to just 1mm.
The steel sections were then bolted together making them more robust to resist fatigue induced stresses.
Boaters travelling between the Union and Forth and Clyde canals pass first along the 2km extension of the Union Canal, itself a rare 'contour canal' which was originally built on one level with no locks along its main length apart from the original linking flight of 11 locks at Falkirk.
The canal extension ends in a double staircase lock which lowers boats seven metres to a holding basin. From here, the boats pass beneath a bridge carrying the main Edinburgh to Glasgow railway line.
They then enter what was Britain's first new canal tunnel to be built for over a century. This 168 metre long canal tunnel was driven with great care beneath the Roman Antonine Wall, itself a World Heritage site.
From the Roughcastle Tunnel, boats emerge to cross a 104 metre long aqueduct with a trough appearing to 'fly' through circular hoops. The aqueduct runs directly onto the Wheel's upper gondola.
Sea to sea canal
The structure uses 14,868 bolts
Below, similar gates release boats into the basin where, through a single lock, they drop the final three metres to join the Forth and Clyde Canal, Scotland's oldest canal.
At its completion, this was the world's first sea to sea ship canal.
Views from the top can extend as far as 40 miles on a clear day.
The panorama includes Ben Lomond and the beginnings of The Trossachs, the Wallace Monument in Stirling, the Ochil Hills and the River Forth through to Grangemouth Docks.
British Waterways Scotland, Falkirk Council and Central Scotland Forest Trust are working on the Helix Project.
This will transform 300 hectares of disused land between Grangemouth and Falkirk into a huge eco park.
A focal point of the new Helix will be a canal extension at the entrance to the sea lock and this new waterway will be heralded by two giant, 30 metre high 'Kelpie' or mythical seahorse sculptures by renowned Scottish artist Andy Scott."