The Hidden Engineering Behind the Falkirk Wheel

0:01 This is the Forth and Clyde Canal in central Scotland.

0:06 Completed in 1790, it was the first canal

0:08 to cross any part of the British Isles.

0:11 There are a lot of geographical terms for coastal

0:14 features where the sea indents into the land:

0:18 sounds, inlets, fjords, lochs, coves, bays, and so on.

0:21 They all have subtly different meanings

0:24 that can vary by location, but in Scotland, a lot of them are called “firths,”

0:28 and they’re pretty important when it comes to navigation.

0:31 The Forth and Clyde Canal, as its name strongly suggests,

0:34 connects the Firth of Forth to the Firth of Clyde.

0:37 It also has a branch into the heart of Glasgow.

0:40 When it was built, this canal dramatically shortened

0:43 the transit times for goods in the region,

0:46 and it also served as the testing waters for the very first steam-powered boats.

0:50 Not long after the Forth and Clyde opened,

0:53 another important canal was completed in Scotland.

0:55 The Union Canal connected the cities of Falkirk and Edinburgh,

0:59 opening up a route for coal and other minerals

1:02 from the mines and quarries around Lanarkshire to the capital.

1:05 Along the way, it passes over some pretty impressive aqueducts,

1:09 including the Avon Aqueduct near Linlithgow.

1:11 A connection to the Forth and Clyde Canal in Falkirk

1:15 would provide a direct waterway link between the two

1:18 largest cities in the country (Edinburgh and Glasgow) without

1:22 ships needing to navigate the hazardous Firth of Forth.

1:25 But there is the challenge of elevation.

1:27 Union Canal sits about 115 feet or 38

1:31 meters above the level of the Forth and Clyde.

1:35 Moving people and goods by boat has a lot of advantages: it’s cheap,

1:39 it’s efficient, it usually takes less infrastructure,

1:41 and it allows for connectivity across the globe.

1:44 But there is a major disadvantage:

1:46 the waterways that ships and boats traverse have to be pretty much level.

1:51 Boats don’t climb hills like cars, trucks, and trains.

1:54 This is the main purpose of a lock:

1:57 raising or lowering a vessel to navigate elevation changes in waterways.

2:01 In fact, locks are pretty much the only solution

2:04 to this engineering challenge… except in a few rare cases.

2:08 You’ve seen the title.

2:09 You know where I’m headed with this.

2:11 But the story of the Falkirk Wheel- the only

2:13 rotary boat lift in the world- is fascinating,

2:16 not just because of the mechanisms,

2:18 but also how it came to be in the first place.

2:22 It’s not easy to accomplish projects like this.

2:24 The Falkirk Wheel is not the passion project of some lone eccentric billionaire.

2:29 This is public infrastructure,

2:30 which means a vast array of stakeholders had to come together and agree

2:35 that this bizarre structure was worth the resources that went into building it.

2:39 It’s got some very clever engineering under the hood,

2:42 and a lot of lessons in its creation that, I think,

2:46 apply to other challenges we face today.

2:49 I’m Grady, and this is Practical Engineering.

3:01 Of course, the original connection between the Forth

3:04 and Clyde and Union canals did use locks.

3:07 A lot of locks.

3:08 This map from 1898 shows the flight of 11 locks

3:12 required to get boats up and down between the two.

3:16 You can imagine the time, resources,

3:18 and effort involved in navigating this staircase.

3:21 The process took the better part of a day,

3:24 and not only that, it used a lot of water from the Union Canal.

3:28 Even though boats can move through locks in both directions,

3:32 water only moves through in one.

3:34 Each structure always fills from the upper canal,

3:37 and always drains to the lower one.

3:39 That’s just gravity.

3:40 But, it’s important to realize that even though most locks don’t use pumps,

3:45 the energy required to raise and lower boats through isn’t free.

3:49 Each passage through costs roughly one

3:51 “lock-full” of water from the upper canal.

3:54 In addition to the inconvenience and water usage,

3:57 other factors eventually drove these canal

3:59 systems in Scotland into disrepair and abandonment.

4:02 The canals were small, and as ships got larger,

4:05 the narrow and shallow passages became

4:08 less useful for transporting materials and goods.

4:11 The railroads also started competing with the canals,

4:14 offering faster connections between major cities.

4:17 By 1930, the canals were barely used,

4:20 and by 1960, they were choked with vegetation and debris.

4:24 Motorway construction disconnected several segments,

4:26 and authorities decided to close them for good.

4:29 That could have been the end of the story,

4:32 and honestly, it wouldn’t be too surprising.

4:34 It’s been the fate of many of the world's great canals

4:37 and inland waterways as transportation technologies

4:39 and overland shipping have passed them by.

4:43 But then the year 2000 happened.

4:47 Maybe you remember this.

4:48 It was a weird time to be alive.

4:51 There was this strange tension between excitement about the new century

4:55 and fear that all our computer systems would crash into an apocalypse.

4:59 The programmers and IT professionals took good care of us on the computer side,

5:04 but there were people working hard on the celebrations, too.

5:08 One of those organizations was the United Kingdom’s Millennium Commission.

5:12 The idea was simple:

5:14 take some of the money from the National Lottery and direct it toward

5:18 interesting and impactful projects that would help mark the turn of the century.

5:22 In Scotland, a large consortium of organizations- public, private,

5:26 and volunteers- got together and applied

5:29 for a grant from the Millennium Commission.

5:31 In 1997, funding was awarded to cover approximately

5:35 half of the cost of the Millennium Link:

5:38 a massive undertaking to revitalize and reopen the canals

5:42 that once connected Scotland from coast to coast,

5:45 restore locks, build hike-and-bike trails, and rehabilitate bridges.

5:49 The work included The Kelpies, a sculpture of two huge horse heads that serve

5:54 as the gateway to the Forth and Clyde canal.

5:57 That was a pretty fascinating civil engineering project in its own right.

6:01 But of course, the Millennium Link’s flagship project was

6:04 reconnecting the Forth and Clyde to the Union Canal.

6:08 But rather than do it with locks,

6:10 the group wanted a 21st-century landmark, or I guess, more of a watermark.

6:15 A fast, efficient connection that would serve

6:18 as a capstone to the canal revitalization, draw tourists from around the world,

6:23 and serve as a symbol of the region that was

6:26 once a hub of transportation and commerce in Scotland.

6:28 And, in fact, a hub is a good metaphor for what they came up with.

6:34 The Falkirk Wheel opened for traffic in May 2002, and now,

6:38 more than two decades later, it’s pretty clear that they nailed the idea.

6:42 Here’s how it works:

6:43 Boats bound for the Union Canal enter a circular turning basin at the bottom.

6:48 The Wheel has two opposed arms,

6:50 each with water-filled gondolas (or caissons) spanning between them.

6:55 Those gondolas are mounted on bearings that ride on circular rails.

6:59 When one goes up, the other comes down, so traffic can move both ways.

7:04 The wheel is driven at its center using

7:07 hydraulic motors that keep the motion smooth and slow.

7:10 Idler pinions mesh between two identical ring gears:

7:13 one fixed and centered on the shaft; the other surrounding each gondola.

7:18 This arrangement enables the gondolas to counter-rotate as the wheel moves,

7:23 maintaining their perfect upright position throughout the full range of motion.

7:28 The elegance of the Falkirk Wheel hides

7:31 some fairly complicated systems that make it function.

7:34 At the top and bottom,

7:35 each gondola has to be able to open and close to let boats in and out.

7:40 And the aqueduct at the top needs the same capability so

7:43 water doesn’t just flow off the edge when the wheel is moving.

7:46 The docking and undocking procedure is a delicate dance.

7:51 When a gondola reaches the top position, stow pins extend to lock it in place.

7:57 Then an extendable lance connects it to a hydraulic power unit.

8:01 A U-shaped seal extends to bridge the gap between the two structures,

8:05 and pipes fill the gap between the gates with water, balancing the pressure.

8:10 Finally, hydraulic rams open the gates on both sides,

8:14 allowing boats to enter or leave.

8:16 The whole process happens in reverse, and then the wheel is free to move again.

8:20 Part of the engineering genius of the Falkirk

8:23 Wheel is that it’s always balanced,

8:25 whether there are boats inside the gondolas or not.

8:29 This is one of those confusing things about buoyancy:

8:32 a floating vessel always displaces its own weight in water.

8:37 Theoretically, as long as the water level stays the same,

8:40 when a boat floats over an aqueduct,

8:42 there is no change in forces on the columns.

8:45 The displaced water flows away, balancing the new force of the boat.

8:50 Same thing for the gondolas.

8:51 When a boat floats in, its weight in water flows out,

8:55 maintaining a balance between the two sides.

8:57 As a result, the Falkirk Wheel doesn’t really require a lot of power to operate.

9:03 It’s about one-and-a-half kilowatt-hours for a half turn of the wheel,

9:06 often compared to the power required to boil eight kettles of water.

9:10 Where I live, that’s less than 25 cents in electricity.

9:13 And unlike the day-long climb of the industrial-revolution-era locks,

9:17 the Wheel moves boats between levels in about five minutes.

9:22 The Scottish Canals see almost no commercial shipping these days.

9:26 They’re still too small, and the road and rail networks are still faster.

9:30 But the canals do see a lot of traffic.

9:33 There’s a whole class of vessels specifically designed

9:36 for navigating the unique and historic canals of the UK.

9:40 Similar to RV culture in the US,

9:43 narrowboats ply the inland waters across England,

9:46 Wales, Scotland, and beyond, used for holidays,

9:48 touring, and even as long-term homes.

9:51 During the early Industrial Revolution,

9:53 boats like this were pulled along canals by horses

9:57 or donkeys from towpaths that ran alongside them.

10:00 Modern narrowboats are self-propelled and often equipped with domestic comforts,

10:05 including bathrooms, kitchens, heating, and internet.

10:08 The number of boats has been steadily increasing over the past decade,

10:12 offering the freedom and lower cost of a nomadic lifestyle on the canals.

10:17 Even for those not living on narrowboats,

10:19 cruises and tours along the canals offer something unique.

10:23 It’s a totally different way to experience the landscape

10:26 in some of Great Britain’s most beautiful areas,

10:28 and it offers insights into the history

10:31 of the region that you can’t get anywhere else.

10:34 And of course, you also get to see the fascinating infrastructure,

10:38 including a boat lift that you won’t find anywhere else in the world.

10:43 But it doesn’t go all the way up.

10:45 When a segment of the canal was relocated as part of the Millennium Link,

10:49 it needed to cross the Antonine Wall,

10:51 a Roman-era defensive perimeter and UNESCO World Heritage Site.

10:55 Rather than disturb it, the new canal was built into a tunnel below.

11:00 From the aqueduct at the top of the Wheel,

11:03 two new locks raise boats the remaining distance once they

11:06 pass underneath the wall to the top of the Union Canal.

11:10 The Antonine Wall marked the far northern border of the Roman Empire.

11:14 On another edge, just a handful of decades before it was built,

11:19 Mount Vesuvius erupted, burying the city of Pompeii in ash.

11:22 But there’s a twist to that story.

11:24 My friends at the podcast, RadioLab,

11:26 are just about to premiere a fantastic video about the survivors

11:30 of Pompeii and how we discovered that some people actually escaped.

11:35 This simultaneous release is part

11:37 of a collaboration with the Independent Media Initiative

11:40 to highlight some of the best educational and artistic creators on the internet.

11:45 I’m really thankful for the award the channel

11:47 won this year for my Practical Construction special,

11:50 and I’m so excited to hand off to one of my favorite shows on the internet,

11:55 RadioLab, for the next video in this collaboration.

11:58 Go check it out after this!

12:00 When I was a kid, my dad used to tell me,

12:03 “If the only reason you want something is because it’s cool,

12:05 you probably don’t need it.” You can look at me

12:08 and probably tell I took that advice to heart.

12:11 But there are situations where it’s worth doing

12:14 something just because it’s going to be impressive.

12:17 The Falkirk Wheel is a perfect example.

12:20 Locks are a perfectly functional solution to get

12:23 boats up and down to different elevations.

12:25 There are thousands of them around

12:28 the world diligently serving our inland waterways.

12:31 Scotland wanted something special,

12:33 something that would spark a resurgence in their canal system

12:36 and revitalize the sense of pride in the communities along them.

12:40 It took guts to try something completely different, and it paid off.

12:45 Millions of people have visited to watch it turn or travel through it.

12:49 The Falkirk Wheel didn’t just reconnect two canals.

12:52 It reconnected people with the idea that infrastructure

12:56 can be both useful and pretty cool.

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14:47 Thank you for watching and let me know what you think.