The Hidden Engineering Behind the Falkirk Wheel

[00:01] This is the Forth and Clyde Canal in  central Scotland. Completed in 1790,   it was the first canal to cross any part of the  British Isles. There are a lot of geographical   terms for coastal features where the sea indents  into the land: sounds, inlets, fjords, lochs,  

[00:20] coves, bays, and so on. They all have subtly  different meanings that can vary by location,   but in Scotland, a lot of them are called  “firths,” and they’re pretty important when it   comes to navigation. The Forth and Clyde Canal, as  its name strongly suggests, connects the Firth of  

[00:36] Forth to the Firth of Clyde. It also has a branch  into the heart of Glasgow. When it was built,   this canal dramatically shortened the  transit times for goods in the region,   and it also served as the testing waters  for the very first steam-powered boats.

[00:50] Not long after the Forth and Clyde opened,  another important canal was completed in   Scotland. The Union Canal connected  the cities of Falkirk and Edinburgh,   opening up a route for coal and other minerals  from the mines and quarries around Lanarkshire to  

[01:04] the capital. Along the way, it passes over some  pretty impressive aqueducts, including the Avon   Aqueduct near Linlithgow. A connection to the  Forth and Clyde Canal in Falkirk would provide   a direct waterway link between the two largest  cities in the country (Edinburgh and Glasgow)  

[01:21] without ships needing to navigate the hazardous  Firth of Forth. But there is the challenge of   elevation. Union Canal sits about 115 feet or 38  meters above the level of the Forth and Clyde.

[01:35] Moving people and goods by boat has a lot  of advantages: it’s cheap, it’s efficient,   it usually takes less infrastructure, and it  allows for connectivity across the globe. But   there is a major disadvantage: the waterways that  ships and boats traverse have to be pretty much  

[01:50] level. Boats don’t climb hills like cars, trucks,  and trains. This is the main purpose of a lock:   raising or lowering a vessel to navigate  elevation changes in waterways. In fact,  

[02:02] locks are pretty much the only solution to this  engineering challenge… except in a few rare cases. You’ve seen the title. You know where  I’m headed with this. But the story of   the Falkirk Wheel - the only rotary boat lift in  the world - is fascinating, not just because of  

[02:17] the mechanisms, but also how it came to be in the  first place. It’s not easy to accomplish projects   like this. The Falkirk Wheel is not the passion  project of some lone eccentric billionaire.  

[02:29] This is public infrastructure, which means a vast  array of stakeholders had to come together and   agree that this bizarre structure was worth the  resources that went into building it. It’s got   some very clever engineering under the hood, and  a lot of lessons in its creation that, I think,  

[02:46] apply to other challenges we face today. I’m  Grady, and this is Practical Engineering.

[03:01] Of course, the original connection between  the Forth and Clyde and Union canals did use   locks. A lot of locks. This map from 1898 shows  the flight of 11 locks required to get boats up  

[03:14] and down between the two. You can imagine  the time, resources, and effort involved in   navigating this staircase. The process took  the better part of a day, and not only that,   it used a lot of water from the Union Canal.  Even though boats can move through locks in  

[03:31] both directions, water only moves through in one.  Each structure always fills from the upper canal,   and always drains to the lower one. That’s  just gravity. But, it’s important to realize   that even though most locks don’t use pumps, the  energy required to raise and lower boats through  

[03:48] isn’t free. Each passage through costs roughly  one “lock-full” of water from the upper canal. In addition to the inconvenience and water usage,  other factors eventually drove these canal systems   in Scotland into disrepair and abandonment. The  canals were small, and as ships got larger, the  

[04:06] narrow and shallow passages became less useful for  transporting materials and goods. The railroads   also started competing with the canals, offering  faster connections between major cities. By 1930,  

[04:18] the canals were barely used, and by 1960, they  were choked with vegetation and debris. Motorway   construction disconnected several segments, and  authorities decided to close them for good. That  

[04:30] could have been the end of the story, and  honestly, it wouldn’t be too surprising.   It’s been the fate of many of the world's great  canals and inland waterways as transportation   technologies and overland shipping have passed  them by.

[04:43] But then the year 2000 happened. Maybe you remember this. It was a weird time  to be alive. There was this strange tension   between excitement about the new century and fear  that all our computer systems would crash into an  

[04:59] apocalypse. The programmers and IT professionals  took good care of us on the computer side,   but there were people working hard  on the celebrations, too. One of   those organizations was the United Kingdom’s  Millennium Commission. The idea was simple:  

[05:14] take some of the money from the National  Lottery and direct it toward interesting   and impactful projects that would  help mark the turn of the century. In Scotland, a large consortium of organizations  - public, private, and volunteers - got together  

[05:28] and applied for a grant from the Millennium  Commission. In 1997, funding was awarded to cover   approximately half of the cost of the Millennium  Link: a massive undertaking to revitalize  

[05:40] and reopen the canals that once connected  Scotland from coast to coast, restore locks,   build hike-and-bike trails, and rehabilitate  bridges. The work included The Kelpies,  

[05:52] a sculpture of two huge horse heads that serve as  the gateway to the Forth and Clyde canal. That was   a pretty fascinating civil engineering project  in its own right. But of course, the Millennium   Link’s flagship project was reconnecting  the Forth and Clyde to the Union Canal.

[06:08] But rather than do it with locks, the group wanted  a 21st-century landmark, or I guess, more of a   watermark. A fast, efficient connection that would  serve as a capstone to the canal revitalization,  

[06:21] draw tourists from around the world, and serve  as a symbol of the region that was once a hub   of transportation and commerce in Scotland.  And, in fact, a hub is a good metaphor for   what they came up with. The Falkirk Wheel  opened for traffic in May 2002, and now,  

[06:38] more than two decades later, it’s pretty clear  that they nailed the idea. Here’s how it works: Boats bound for the Union Canal enter a circular  turning basin at the bottom. The Wheel has two  

[06:50] opposed arms, each with water-filled gondolas (or  caissons) spanning between them. Those gondolas   are mounted on bearings that ride on circular  rails. When one goes up, the other comes down,  

[07:02] so traffic can move both ways. The wheel is  driven at its center using hydraulic motors   that keep the motion smooth and slow. Idler  pinions mesh between two identical ring gears:   one fixed and centered on the shaft;  the other surrounding each gondola.  

[07:18] This arrangement enables the gondolas  to counter-rotate as the wheel moves,   maintaining their perfect upright position  throughout the full range of motion. The elegance of the Falkirk Wheel hides  some fairly complicated systems that make  

[07:33] it function. At the top and bottom, each  gondola has to be able to open and close   to let boats in and out. And the aqueduct at  the top needs the same capability so water   The docking and undocking procedure is a delicate dance.

[07:51] When a gondola reaches the top  position, stow pins extend to lock it in place.   Then an extendable lance connects it to a  hydraulic power unit. A U-shaped seal extends  

[08:03] to bridge the gap between the two structures, and  pipes fill the gap between the gates with water,   balancing the pressure. Finally, hydraulic rams  open the gates on both sides, allowing boats   to enter or leave. The whole process happens in  reverse, and then the wheel is free to move again.

[08:20] Part of the engineering genius of the Falkirk  Wheel is that it’s always balanced, whether   there are boats inside the gondolas or not. This  is one of those confusing things about buoyancy:  

[08:32] a floating vessel always displaces its  own weight in water. Theoretically,   as long as the water level stays the same, when a  boat floats over an aqueduct, there is no change   in forces on the columns. The displaced water  flows away, balancing the new force of the boat.  

[08:50] Same thing for the gondolas. When a boat  floats in, its weight in water flows out,   maintaining a balance between the two sides. As a  result, the Falkirk Wheel doesn’t really require a   lot of power to operate. It’s about one-and-a-half  kilowatt-hours for a half turn of the wheel,  

[09:06] often compared to the power required to  boil eight kettles of water. Where I live,   that’s less than 25 cents in electricity.  And unlike the day-long climb of the   industrial-revolution-era locks, the Wheel moves  boats between levels in about five minutes.

[09:22] The Scottish Canals see almost no commercial  shipping these days. They’re still too small,   and the road and rail networks are still faster.  But the canals do see a lot of traffic. There’s   a whole class of vessels specifically designed  for navigating the unique and historic canals  

[09:38] of the UK. Similar to RV culture in the US,  narrowboats ply the inland waters across England,   Wales, Scotland, and beyond, used for holidays,  touring, and even as long-term homes. During the  

[09:52] early Industrial Revolution, boats like  this were pulled along canals by horses   or donkeys from towpaths that ran alongside  them. Modern narrowboats are self-propelled   and often equipped with domestic comforts,  including bathrooms, kitchens, heating,  

[10:07] and internet. The number of boats has been  steadily increasing over the past decade,   offering the freedom and lower cost  of a nomadic lifestyle on the canals. Even for those not living on narrowboats,  cruises and tours along the canals offer  

[10:22] something unique. It’s a totally different way  to experience the landscape in some of Great   Britain’s most beautiful areas, and it offers  insights into the history of the region that   you can’t get anywhere else. 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. But it doesn’t go all the way up. When  a segment of the canal was relocated   as part of the Millennium Link, it  needed to cross the Antonine Wall,  

[10:51] a Roman-era defensive perimeter and UNESCO World  Heritage Site. Rather than disturb it, the new   canal was built into a tunnel below. From the  aqueduct at the top of the Wheel, two new locks  

[11:04] raise boats the remaining distance once they pass  underneath the wall to the top of the Union Canal. The Antonine Wall marked the far northern  border of the Roman Empire. On another edge,   just a handful of decades before it  was built, Mount Vesuvius erupted,  

[11:20] burying the city of Pompeii in ash. But there’s  a twist to that story. My friends at the podcast,   RadioLab, are just about to premiere a fantastic  video about the survivors of Pompeii and how we  

[11:32] discovered that some people actually escaped. This  simultaneous release is part of a collaboration   with the Independent Media Initiative to highlight  some of the best educational and artistic creators  

[11:44] on the internet. I’m really thankful for the  award the channel won this year for my Practical   Construction special, and I’m so excited to hand  off to one of my favorite shows on the internet,   RadioLab, for the next video in this  collaboration. Go check it out after this!

[12:00] When I was a kid, my dad used to tell me,  “If the only reason you want something is   because it’s cool, you probably don’t need  it.” You can look at me and probably tell   I took that advice to heart. But there are  situations where it’s worth doing something  

[12:14] just because it’s going to be impressive. The  Falkirk Wheel is a perfect example. Locks are   a perfectly functional solution to get boats  up and down to different elevations. There  

[12:26] are thousands of them around the world  diligently serving our inland waterways.   Scotland wanted something special, something  that would spark a resurgence in their canal   system and revitalize the sense of pride in  the communities along them. It took guts to  

[12:42] try something completely different, and it  paid off. Millions of people have visited to   watch it turn or travel through it. The  Falkirk Wheel didn’t just reconnect two   canals. It reconnected people with the idea that  infrastructure can be both useful and pretty cool.

[13:01] Here’s something else that’s pretty cool:  a homecooked meal that’s seasonal, healthy,   and didn’t require a trip to the grocery  store. We’ve been using today’s sponsor,   HelloFresh, for years now, even  before these ones were born. And  

[13:14] now they’re actually old enough  to help out with dinner… kind of. “Oh, some snail shells. Put them in the pot!” pre-portioned ingredients shipped right to  your door so you have dinners ready to go.

[13:30] These helpers can be a bit picky, but  HelloFresh has expanded their options   and even made them customizable to  fit the preferences of the week.

[13:42] “Just put the pepper on momma’s  croutons. I like it spicy.  And in fact, HelloFresh has kid-friendly  choices that are specifically curated  

[13:54] for the little ones that don’t like  to stray from the staples like I do. “Don’t mind the man saying ‘Oh  no’ repeatedly in the background.” Even beyond the good food, using Hello  Fresh is just a great way to spend time  

[14:09] keeps them involved, and (I think)  makes them more likely to try new foods. “I’m cooking mushrooms on the stove!”

[14:22] Give a second chance to the ‘NEW’  HelloFresh by using my code PRACTICALFM   at HelloFresh dot com for 10 Free Meals +  Free Breakfast for Life. This part’s verbatim:  

[14:34] One free meal per box with active subscription.  Free meals applied as discount on first box,   new or returning subscribers only, varies by  plan. Sign up today! Click the link below or   use my code PRACTICALFM at HelloFresh.com. Thank  you for watching and let me know what you think.