Archimedes and a Boat Lift: the Falkirk Wheel

Archimedes and a Boat Lift: the Falkirk Wheel


This is the Falkirk Wheel, and it’s one of
the greatest bits of modern industrial design in the world. On the top of that hill is the Union Canal,
and down here is the Forth and Clyde Canal. And the traditional way to get boats between
them was a flight of locks, which’d take about a day to get through, and besides, they were
dismantled here in the 1930s. The solution: the world’s only rotating boat lift. Now boat lifts aren’t a new thing. They’ve
been around for centuries. Most of them, like this, have two caissons, which is the technical
term for the tubs that the boats sit in, although usually they’re next to each other rather
than rotating round a central point. And the reason for two is this: to lift 500 tonnes
of water 24 metres up, you need a minimum of 32 kilowatt-hours of power. That’s about
what an average British house uses in three days, or an average American house in one
day. And that’s before friction, that’s just the potential energy you need to put into
the system to raise it up that far. But: if you’re also having the same weight of water
descend at the same rate, at the same time, then you’re not adding any potential energy
at all. On average, nothing is going up or down. You’re just getting a really heavy thing
moving, and then stopping it again. Because of that, this wheel only needs one and a half
kilowatt-hours for one lift: less than a twentieth of what it’d need otherwise. There are even some boat lifts in the world
powered entirely by gravity, where local conditions and the architecture permit it: you just fill
the top one with a bit more water, let it go, and then apply the brakes when you need
to. Bit tricky with something that’s as fancy as this though. It has to be massively reinforced,
there is an incredible amount of momentum there. And here’s the really clever bit: remember
Archimedes’ principle, the Greek bloke with the bathtub. A floating object displaces an
amount of water equal to its weight. An object that sinks, sure, that displaces equal to
volume, but a floating object like a boat displaces water equal to its weight. When
they’re full of water, those caissons weigh about 500 tonnes. You add ten tons of floating
boat into one of them, then ten tons of water flows out into the canal. Which means this is balanced no matter how
much is actually floating in it. [Translating these subtitles? Add your name here!]

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  1. Lovely subject, fascinating. What I love more is how short, sweet and to the point this video was. Less than 3 minutes and I have everything I ever wanted out of this and more. THANK YOU!

  2. Hi Tom
    We are on a trip through scotland right now and because of your video we took a trip on a boat passing the Falkirk Wheel. For an Engeneer this was an absolute blast.

    Keep on making these amasing videos.

    Yours
    Daniel

  3. Ah yes, the Greek bloke with the bathtub. I also like the Italian guy with a telescope and the English dude with the falling apple.

  4. Uhm, actually, the same principle is used in other Boatlifts too. Maybe not the designer solution as there, but for example the "Schiffshebewerk" in Niederfinow, Germany is based on the same principle, only that it uses concrete weights on the other side to balance it out.

  5. 1 1/2 KWh is 3 e-bike batteries. Those little black bricks that power a relatively lightweight and small bicycle around…

    A Tesla Model S has up to 100Kwh and only weighs 2 1/2 tonne or so… go figure.

  6. 0:50 finds a way to take a dig at Americans. Still cant get over the fact that they wanted nothing to do with your faggy little circle jerk commonwealth? Awww.

  7. well in theory they could generate electricity, it's just a matter of balance or imbalance; allow some of the water to drain from the bottom carrier while going up.

  8. "[…] Kilowatt-hours of power"

    Naughty naughty, using a unit of energy in the context of power? Someone skipped physics

  9. That's not far fae Edinburgh and it's an amazing bit of engineering, Scotland is a great place to be! πŸ€—πŸ€—πŸ€—πŸ€—πŸ€—πŸ€—πŸ€—πŸ€—πŸ΄σ §σ ’σ ³σ £σ ΄σ ΏπŸ΄σ §σ ’σ ³σ £σ ΄σ ΏπŸ΄σ §σ ’σ ³σ £σ ΄σ ΏπŸ΄σ §σ ’σ ³σ £σ ΄σ ΏπŸ΄σ §σ ’σ ³σ £σ ΄σ ΏπŸ΄σ §σ ’σ ³σ £σ ΄σ ΏπŸ΄σ §σ ’σ ³σ £σ ΄σ ΏπŸ΄σ §σ ’σ ³σ £σ ΄σ Ώ

  10. Maybe they could dump water from the bottom bathtub as they begin slowing it down and then dump the same volume of water from the top one as it comes to a stop. Gravity assisted braking.

  11. That was a great video very succinct well-prepared and interesting. Thank you very much from a new subscriber

  12. Only works on a flat earth πŸŒŽπŸ˜‚water cannot bend over hills it simply only lays flat. Or please do prove otherwise
    P. S gravity is a theory so don't use that nonsense

  13. Americans use more electricity because they're more technologically advanced and have more money. I wish I lived there instead of the UK.

  14. I guess I'm very late to the party here, but for another world-unique feat of engineering on the British canals, are you aware of the Barton Swing Aqueduct?

  15. I have to say this is an extremely cool engineering feat! I am in awe of the people who have the kind of brains to figure this stuff out!

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