The Falkirk Wheel

I love a good engineering problem, whether it's tinkering with gadgets around the house or studying the complexities of bigger projects such as the London Eye, Sydney Opera House, the Spinnaker Tower in Portsmouth. Or the whole of Venice. I can't drive past a simple damn without stopping to have a look. I enjoy driving over bridges of any size, from the Europabrücke in Austria to the toll bridge in Southampton. My wife has term she uses for this affliction - in fact, she uses many different words, none intended as compliments (though I often take them as such, just to wind her up).

So naturally I was intrigued when I found out about this amazing feat of modern engineering. Faced with the problem of connecting two canals, one of which was 35m higher than the other, the Brits came up with this ingenious solution: an elevator for boats!

But since I know very little about it, here is some information from their website, www.thefalkirkwheel.co.uk:

The Millennium Link was an ambitious £84.5m project with the objective of restoring navigability across Scotland on the historic Forth & Clyde Canal and the Union Canal, providing a corridor of regenerative activity through central Scotland. One major challenge in this objective was the fact that the Forth and Clyde Canal lay 35m (115ft) below the level of the Union Canal.

Historically, the two canals had been joined at Falkirk by a flight of 11 locks that stepped down across a distance of 1.5km, but these has been dismantled in 1933, breaking the link. What was required was a method of connecting the two canals by some means of lifting two boats down the 35m drop as quickly and simply as possible. The resultant, perfectly balanced structure that is the world’s first rotating boat lift.

The Falkirk Wheel lies at the end of a reinforced concrete aqueduct that connects, via the Roughcastle tunnel and a double staircase lock, to the Union Canal. Boats entering the Wheel’s upper gondola are lowered, along with the water that they float in, to the basin below. At the same time, an equal weight rises up, lifted in the other gondola. This works on the Archimedes principle of displacement. That is, the mass of the boat sailing into the gondola will displace an exactly proportional volume of water so that the final combination of ‘boat plus water’ balances the original total mass.

Each gondola runs on small wheels that fit into a single curved rail fixed on the inner edge of the opening on each arm. In theory, this should be sufficient to ensure that they always remain horizontal, but any friction or sudden movement could cause the gondola to stick or tilt. To ensure that this could never happen and that the water and boats always remain perfectly level throughout the whole cycle, a series of linked cogs acts as a back up.