Burj Al Arab Richard Hammond's Engineering Connections


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Burj Al Arab

Richard Hammond looks at how Dubai's sail-shaped hotel Burj Al Arab was built, including creating sea defences and coping with steel expansion due to extreme heat.


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It's one of the most striking buildings in the world.

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In its short life, its distinctive shape

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has made it an icon for Dubai...

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..recognised the world over.

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It's the Burj Al Arab, or Arabian Tower.

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This is the tallest atrium in the world, 182 metres high.

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And that's just the beginning of the superlatives

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in one of THE most opulent hotels in the universe.

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There's enough gold and marble in here to make a rapper look dowdy.

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But behind the bling are some truly remarkable engineering achievements.

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They wouldn't have been possible without...

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..the children's game of jacks...

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..an engine cam...

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..the pages of a phone book...

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Ha-ha!

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..a revolution in fire hose design...

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Look at that!

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..and a camera flash.

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-I see your point. That is a potential problem.

-Yeah.

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Cor blimey!

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Obviously, you don't usually see this bit

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but this is how I start every day's work, this is how we do things.

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Arriving by helicopter is par for the course here.

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Thank you.

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'I'm only doing it to blend in as I'm about to check in...'

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Thank you.

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'..to check out one of the most distinctive architectural achievements in the world.'

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-Thank you.

-Would you like some Arabic coffee?

-I'd love some, thank you.

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Cheers!

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Inside, the suites really are luxurious cocoons,

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sheltering you from the desert outside.

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There really is no sand in here.

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Unless you really want it, I'm sure room service could oblige.

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And then, while your bags are being unpacked for you,

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somewhere in your vast suite,

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you can stride around and look out over the whole of Dubai.

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But perhaps, as importantly, the whole of Dubai

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can look back at the hotel.

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Because this place was designed right from the start to be an icon.

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In the last 20 years, Dubai has shot upwards and outwards,

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looking to find its fortune through business and tourism.

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Oil was discovered in the early '60's

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but people here know it won't last forever.

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The iconic Burj Al Arab is part of Dubai's planned future...

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after oil.

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The architects on the project, however,

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were inspired by Dubai's past.

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Once upon a time, Dubai's wealth came from the sea,

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where they harvested pearls.

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And this building's distinctive shape recalls that history.

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That curve is inspired by dhows, the traditional sailing boats

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that have plied these waters since ancient times.

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Making an iconic building look like a ship

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was only part of the challenge.

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The architects wanted something more.

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They needed a statement.

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The solution, well, put your building 300 metres out to sea

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on its own tailor-made private island.

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Of course it's not going to be cheap or easy.

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Engineers had to make an island

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big and solid enough to hold a quarter of a million-ton tower.

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Most of all, they had to protect it from the sea

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and the power of the waves.

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Even this placid-looking gulf can have a dangerous temper

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which could easily wash away a man-made island.

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Back in the UK, I'm going to attempt

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to show how even a relatively small amount of water

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can do a surprising amount of damage.

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I'm going to create an artificial wave.

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'The man in charge of sea defences at the Burj Al Arab was Mike McNichols.'

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And these things can be pretty powerful?

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In the right circumstances, at the right speed,

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they can act like a solid, smashing into whatever's there.

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This plate glass will test the destructive power of our wave.

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And don't think that this glass is a pushover.

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It's ten mil thick.

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It's the safety stuff they use in tall buildings to stop people falling out.

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It's more than twice as thick as normal window glass.

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This is going to represent our wave - it's a ton of water.

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But it needs one more thing to be like a true wave.

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You need a bit of speed to get this thing going,

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just like a wave pushing through the air.

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Our wave will be set in motion by gravity and explosives.

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You'll like this, it's very subtle.

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At the bottom of the bag is a loop of det-cord, explosive,

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which will explode immediately

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and there will be no bottom on the bag so all this water,

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the whole lot, will fall out in a big solid lump.

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-And that's more like a wave?

-Yes.

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Well, to complete this demonstration of the power of a lump of water,

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I've got this, it's a sort of industrial dining table,

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with a glass top, to give it its full title.

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We will position the bag above there on the crane, fire the explosives, bang, no bottom on the bag,

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all the water comes down in one go on to there.

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And we'll see what happens.

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Part of me thinks even in a solid lump,

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the water will pour round the sides and the biggest problem we'll have is a puddle.

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You'll see, it's going to puncture that glass.

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I'm going to make a suggestion. Whatever happens, let's watch it from over there.

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Now, I have always thought of water as kind of soft stuff,

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which flows around things.

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Sure, in a high-pressure jet, it's good for cleaning the car,

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but a cubic metre of it falling on to thick plate glass?

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Ah, the box.

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I really can't hear a thing now!

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-A nice loud countdown.

-Sorry?

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-A nice loud countdown and press the button.

-Right, this is it for real,

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here is comes, a wave - stand by in five, four,

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three, two, one...

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GLASS SHATTERS

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Well, that was quite a big bang. Thank you for the big bang.

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Yup, too much explosive.

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That's really...

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You can see the thickness of the glass now - ten mil thick, you could stand on that!

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Our ton of water only fell a couple of metres

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and it still had huge destructive power.

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Compared to the power of the waves in the gulf, however, it is a drop in the ocean.

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The biggest waves that batter the artificial island can deliver hundreds of tons of force.

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Each wave can be the equivalent of 130 small cars crashing into it.

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So how do you protect your island from the extreme forces of the waves?

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I think we will take our inspiration, Richard,

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from this little group of jacks here.

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So these are jacks... Forgive me, it seems like quite a leap

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because, how do they take the energy out of the wave?

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This is more a modern version of the jack -

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these things interlock together.

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So the principle is these shapes interlock.

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And the space between them, the water swirls within them,

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and loses its energy.

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-So it's these holes that are doing the work?

-Yeah, the holes.

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It's nothing creates something.

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Holes are the answer, well, sort of.

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Holes were first used in revolutionary jack-shaped sea defences

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created by South African harbour engineers.

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They saw a local version of jacks being played

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and, fascinated by how the jacks interlocked,

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successfully redesigned the harbour defences for East London.

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Almost all coastal defences still rely on this idea of holes,

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including the Burj Al Arab.

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I'm creating a furniture protection system inspired by the sea defences

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used to protect the hotel...

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..in which spaces are the secret ingredient.

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Instead of trying to stop waves dead with a wall,

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the idea was to create a series of spaces -

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holes - that absorb the energy of the sea.

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And we are going to see if the same principle will protect my spare dining table.

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It will be the holes doing the work, I hope.

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We need to clear off out of the way, and let's do it again,

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only this time my table will survive. Probably. ..It's your theory.

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I know!

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Our homemade defences will use the holes in the tyres to redirect the water.

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It will swish around and SHOULD fall harmlessly out the bottom.

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-I have every faith.

-Let's give it a go.

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If we have done our homework right this will save the glass...

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just as it saves the Burj Al Arab's man-made island.

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If we're ready? In five, four,

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three, two, one...

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This is one of those occasions where from seeing something,

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you suddenly really understand it.

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You can see the breakwater break that big lump of water up

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into eddies and swirls and bits.

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-It really was the holes doing the work?

-The holes did all the work.

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Net effect, a protected table, a protected island, a protected hotel.

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Not that my table isn't important.

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In Dubai, the Burj Al Arab engineers used exactly the same principle

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for breaking up waves, except they used concrete, not old tyres.

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Their defences create a smooth, elegant and uniform shape -

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suitable for keeping a world-class hotel's head above water.

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The holes are so good at taking the energy out of waves

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that the island could be built at just seven and a half metres above sea level.

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Keeping the island relatively low allows the architects to continue the illusion

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of a boat on the water.

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But what I think is fascinating is how the architects completed

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the boat itself, inside the sea defences.

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Those are just the outer shell of the island.

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They needed to fill the middle in with something, and they chose... sand.

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I guess it is not in short supply around here, but call me old fashioned...

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I've never thought of sand as the ideal material to make firm foundations for a building...

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especially one that size.

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The Burj Al Arab is 321 metres high -

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slightly taller than the Eiffel Tower.

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How does it possibly stand on sand

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without keeling over in the first stiff breeze?

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Through a remarkably simple scientific principle, in fact.

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Skin friction is exactly what it sounds like -

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it's the friction between the skin, the surfaces of objects.

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If I rub my hands together, friction generates heat, I can feel it.

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Now ordinarily, skin friction is there

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but it's pretty easily overcome.

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So, two pages together, I can feel the friction between them

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but there's not a lot of it.

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However, if I multiply that effect by as many times

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as there are pages in these directories,

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well, let's see what happens.

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I'm going to interleave them page by page. One, two...

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Skin friction is one of the factors

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that keep the Burj Al Arab standing tall.

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'Mind you, I think they built the hotel in less time

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'than it's taking me to do this.'

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1,407...1,408.

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There we go, all done.

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Now, according to the theory, the effects of skin friction

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should have been magnified by as many times

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as there are interfaces between the pages I have interleaved.

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It took a while, but I didn't have much else on this afternoon.

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Knowing how long it took, I'm reluctant to test it, but I'm going to.

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How tough is it?

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HE GRUNTS

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I'm pulling as hard as I possibly can. There is no glue, that is just skin friction.

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There's no way can I pull those apart,

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honestly, I'm trying as hard as I can.

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HE GRUNTS

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No, I need to try harder.

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OK. This should be more like it.

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Obviously skin friction already doing well just to hold this shackle on.

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Remember, nothing holding these together, just the friction between the pages.

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Right, lift it, please.

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How good is skin friction? I mean, really, how good?

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Up!

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OK. Time to demonstrate, if nothing else, my faith in science.

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HE CLEARS THROAT

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Um, yeah, skin friction...

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HE CHUCKLES

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That's all that's holding me up, and the weight of that shackle.

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Remember, no pins in there,

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no tape, no nails, nothing.

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Just friction.

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And friction is also one of the answers to building on unstable material, even sand.

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Otherwise the enormous tower would just topple over.

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The secret was to use reinforced concrete pile foundations,

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which are like long nails driven into the ground.

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They work using skin friction to keep the building in place,

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even in loose sand.

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To show how strong pile foundations can be, a simple demonstration.

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Jar of uncooked rice and a knife.

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Put knife into rice...

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..that's something called skin friction in action.

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Skin friction is strong enough to support a 320 metre tall tower...

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on sand.

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There are six miles of concrete piles bored 43 metres into the sand

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under the hotel to keep it upright and safe.

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Think of each pile as a page in the directory -

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every one makes the bond stronger.

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Combined, they make the sand as solid as a rock,

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and keep the building standing tall.

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In Dubai, temperatures can reach a blistering 49 degrees Celsius.

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And that heat posed a challenge for engineers and architects

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working with steel.

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Metal, like most materials, expands when you heat it up.

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Think about it, if you've got the lid stuck on a jar,

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warm it up and the metal lid will expand and you can free it, that's a good thing.

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But if you're working on giant metal trusses,

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and they're expanding and contracting according to the temperature

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at different times of day and you're trying to fit them together

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in a very precise way, it's going to be tricky.

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The Burj Al Arab was constructed using a steel exoskeleton,

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and external frame.

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The six steel trusses that support the building's weight

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are up to 85 metres long.

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That's longer than a Jumbo Jet.

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In the desert heat, the lengths of steel could expand by 5cm,

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which was critical during construction,

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when everything had to come together exactly.

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These two steel triangles will represent

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the huge steel trusses on the Burj -

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and they really are huge, 80 metres long,

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but the principles will be the same, even at this scale.

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So they've been machined very accurately

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so they can be fixed together using these fixings...

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That goes in there, that mounts in the hole...

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..and one here...

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So that's my steel structure firmly fixed together.

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Fine, but it hasn't yet had to cope with the problems of desert heat

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and the problems of heat expansion associated with it.

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Could be waiting a while here for some desert heat,

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but that's OK, we can bring our own.

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Gas axe, please. Thank you.

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While he's firing that up, I'm going to remove one of these fixings,

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because I want to see the effect of that thermal expansion.

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Right...

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Well, that was, I think we can agree, a hot day.

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But, if I try and put my original fixing back in...

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..and line it up - remember this is machined so the holes should align -

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and...oh, surprise, surprise, they don't,

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there's absolutely no way is that going to go through there.

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Because the metal's expanded, the hole's ended up in the wrong place.

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When the top metal bar undergoes thermal expansion,

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it becomes longer,

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but the bottom one stays the same.

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This means that the holes in each no longer align.

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If this were 80 times bigger,

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imagine the effect it would have then.

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But what can you do about it?

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The steel trusses ARE going to grow and shrink depending upon the time of day and temperature,

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that will happen.

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It could be disastrous, you could end up with a crooked tower.

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The engineers found an ingenious solution,

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thanks to the cam of an engine.

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Cams are used, of course, in car engines, you've probably heard of a camshaft.

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Well, here is one.

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This is the top of the engine,

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this assembly here is to operate the valves,

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which would be in the cylinder bores below.

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They have to open and close very quickly to let fuel and air in,

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and exhaust gases out, that's where the cams come in,

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so I'm going to be the engine turning here,

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and as I rotate the camshaft you can see the cams move eccentrically,

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these lobes where they bulge and stick out push down on this assembly here,

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open the valve and then shut it.

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It's a clever principle

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and one that's been used for a long, long time.

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The off-centre bulge of a cam allows it

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to open and close engine valves on each rotation of the camshaft.

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The builders of the Burj Al Arab borrowed from that idea

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to overcome the problems caused by extreme desert heat.

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This fixing is called an eccentric fixing.

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It's been designed using the same sort of principle -

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this is like a cam inside this hole here.

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And that gives us the flexibility we need

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to cope with this heat expansion.

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So let's put it in, line it up roughly, in the big hole there...

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and if I drop that in,

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we can manoeuvre it around, and there it is -

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that lines up perfectly.

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That's the connection between the engine's cam

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and our fixings for building in the desert.

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The eccentric fixing allows the top hole to be moved,

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so that no matter how much the steel expands,

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it can still be aligned to the bottom hole.

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Engineers at the hotel, taking their inspiration from engine cams,

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designed bespoke moveable fixings that allowed them

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to install the massive trusses accurately,

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despite the thermal expansion.

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Once installed, everything was welded firmly in place.

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Now the building expands and contracts as a whole,

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keeping it in shape.

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In the baking heat of the desert,

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one of the ultimate luxuries

0:22:500:22:52

must be a cool, air-conditioned room.

0:22:520:22:56

Even when temperatures approach 50 Celsius outside,

0:22:570:23:01

the interior of the Burj Al Arab maintains a balmy 23 degrees.

0:23:010:23:07

But keeping it this way isn't as simple as you might think.

0:23:070:23:12

Creating and maintaining an oasis in the desert presented the engineers

0:23:140:23:18

with a series of challenges, right from the very beginning.

0:23:180:23:21

The real problem is managing the big difference

0:23:230:23:26

between temperatures inside and outside the hotel.

0:23:260:23:29

On a hot day, the difference between the two can be 20 degrees Celsius.

0:23:310:23:36

Temperature differences create pressure differences.

0:23:370:23:41

In nature, big pressure differences create violent winds,

0:23:410:23:44

even hurricanes.

0:23:440:23:46

Pressure differences affect all skyscrapers.

0:23:480:23:51

They're especially bad in a structure the size of the Burj Al Arab, in the desert.

0:23:510:23:56

It could literally stop people getting in and out of the building.

0:23:560:24:02

'Back on home soil, Professor of Building Engineering Physics

0:24:030:24:07

'Doug King explains why combining air conditioning,

0:24:070:24:10

'a tall building and a scorching desert can stack up big trouble.'

0:24:100:24:15

Big temperature differences, although they make life nicer inside,

0:24:170:24:21

-they can bring big problems.

-Absolutely. We're going to demonstrate that with this model,

0:24:210:24:25

which is a scale model of the atrium at the Burj.

0:24:250:24:28

I did wonder. It's not as big, is it?

0:24:280:24:30

No, unfortunately, we couldn't get one that big in here,

0:24:300:24:34

so we've had to scale things down. We've got a light bulb at the bottom,

0:24:340:24:37

representing the heat gains from people and the sun shining in the windows.

0:24:370:24:41

And we've got about a kilogram of dry ice on a tray at the top,

0:24:410:24:45

representing the cooling effect of the air conditioning.

0:24:450:24:48

'And the problem is all to do with airflow.

0:24:500:24:53

'An air pellet will show how the air circulates.

0:24:530:24:56

'Heat from people and the sun through the windows on the ground floor cause the air to rise.

0:24:560:25:03

'The air conditioning cools it down, making it more dense, and the air falls...'

0:25:030:25:08

So we've got up-flow on the one side and down-flow on the other side.

0:25:080:25:12

'..leaving you with a tall column of cold, heavy air surrounded by the hot desert,

0:25:120:25:18

'which doesn't sound like a problem.'

0:25:180:25:21

-I still don't see - why the big problem?

-If the building stays closed, it's not a problem.

0:25:210:25:25

The problem happens when we've got this big stack of cold air inside.

0:25:250:25:29

We've got warm air outside, and it's all being held back by the front door.

0:25:290:25:33

-So why don't you open the door and see what happens?

-This door down there?

0:25:330:25:36

-That's the one.

-So I'll open the door...

0:25:360:25:38

-Wooh! Yes!

-What's happening now... See how quickly it's clearing down?

-Yes.

0:25:380:25:42

You've got this big column of cold air inside, much heavier than the air outside,

0:25:420:25:47

-and it's being forced out through that little opening.

-You can see it's rushing out -

0:25:470:25:51

that's not just tumbling out because I've opened the door, that's being pushed out...

0:25:510:25:56

-Right.

-..by this pressure difference.

-See how quickly all that air inside the model

0:25:560:26:00

-has fallen down and pushed the air out.

-So if that's how it works on this scale,

0:26:000:26:04

how big a problem does it represent

0:26:040:26:06

for something the size of Burj Al Arab?

0:26:060:26:08

Well, for something as big as that atrium - it's 180 metres high -

0:26:080:26:11

that's an enormous stack of cold air. Very, very dense at the bottom.

0:26:110:26:15

Opening that door against that pressure is like trying to lift a sack of potatoes.

0:26:150:26:20

To be more precise, the vast atrium at the Burj Al Arab,

0:26:200:26:23

combined with the heat of the desert outside,

0:26:230:26:27

could create the equivalent of 21 bags of sugar pressing against the door.

0:26:270:26:33

So, a 21-kilo weight suspended from a pulley.

0:26:330:26:37

This, then, is about as tough as it would be to open the door at the Burj Al Arab.

0:26:370:26:41

I mean, it's not impossible, but it is a bit of a workout.

0:26:410:26:44

I don't think you want a work out every time you open the door,

0:26:440:26:47

especially if you've saved up to book a suite.

0:26:470:26:50

With the largest atrium in the world,

0:26:510:26:54

this problem is especially acute for the Burj Al Arab.

0:26:540:26:57

The unwanted stack effect was first noticed

0:27:010:27:04

with the rise of the skyscraper.

0:27:040:27:07

Workers in New York and Chicago complained not only of draughts,

0:27:070:27:10

but that they couldn't even open the doors of their buildings

0:27:100:27:14

because of pressure differences inside and outside.

0:27:140:27:17

One solution to the problem is to equalise the pressure inside the building

0:27:190:27:23

with the pressure outside the building.

0:27:230:27:25

But that would mean you'd need to equalise

0:27:250:27:28

the temperature in here with the temperature out there...

0:27:280:27:31

in the desert.

0:27:310:27:32

You wouldn't be able to heat or cool the building.

0:27:320:27:35

And I think having the temperature in here hover around the 40-degree mark

0:27:350:27:39

does rather spoil the whole idea of an oasis in the desert.

0:27:390:27:43

The hotel might lose a star or two for that.

0:27:430:27:46

What you need is a means of getting between two areas of different pressure -

0:27:460:27:51

outside on the street and inside the hotel -

0:27:510:27:54

without allowing the pressures to equalise.

0:27:540:27:57

There was a different solution

0:27:570:28:00

and it came from something inspired by a 19th-century French coal mine.

0:28:000:28:05

In 1839, French mining engineer Jacques Triger overcame the problem

0:28:060:28:11

of moving between two areas of different pressure

0:28:110:28:14

in waterlogged coal mines.

0:28:140:28:16

He created the world's first airlock.

0:28:160:28:19

This is how Triger's system worked. This is my waterlogged ground.

0:28:210:28:24

Well, it's a glass, but you know what I mean.

0:28:240:28:27

Here's my mine shaft.

0:28:270:28:29

If I just sink a mine shaft into waterlogged ground like this,

0:28:290:28:32

it's just full of water at the bottom,

0:28:320:28:34

nobody can work down there.

0:28:340:28:36

The answer to that is

0:28:360:28:37

fairly simple - seal it at the top.

0:28:370:28:39

That stops the air getting out,

0:28:390:28:40

which means the water can't get in.

0:28:400:28:43

That's all well and good until you need to open the top

0:28:430:28:45

to let your workers go down the mine,

0:28:450:28:47

then it flows with water again.

0:28:470:28:51

That answer to that one - establish your dry mine shaft,

0:28:510:28:56

fit an airlock at the top,

0:28:560:28:58

let your workers in.

0:28:580:28:59

Then once they're safely in,

0:28:590:29:00

seal it behind them - everything stays dry, everybody's happy.

0:29:000:29:05

What they needed at the Burj Al Arab was some sort of airlock

0:29:050:29:08

so they could separate the pressure inside the hotel

0:29:080:29:11

from the pressure outside.

0:29:110:29:13

Sounds complicated, like something off a space station.

0:29:130:29:16

But in fact, I've just been through it -

0:29:160:29:18

it's a revolving door.

0:29:180:29:21

Revolving doors are designed in such a way

0:29:220:29:24

that there's never a direct opening to the street.

0:29:240:29:28

The inside is sealed from the outside,

0:29:280:29:30

even when the door is spinning.

0:29:300:29:33

First used in Rector's Restaurant in Times Square in New York in 1899,

0:29:340:29:39

its tagline was, "Always open, always closed",

0:29:390:29:41

because the door keeps a seal, even when you go through it.

0:29:410:29:46

This makes the sort of airlock that's needed

0:29:480:29:51

to stop the big out-rush of air that would happen

0:29:510:29:53

because of the stack effect.

0:29:530:29:55

Now, everyone who can afford it can come and go in comfort.

0:29:550:30:01

But comfort can bring its own difficulties.

0:30:010:30:04

It's probably not surprising

0:30:050:30:07

that pretty much every electronic gizmo conceivable

0:30:070:30:10

has been incorporated into these rooms,

0:30:100:30:12

all operated by remote control.

0:30:120:30:14

At the touch of a button, televisions drop from the ceiling,

0:30:140:30:17

or pop up out of pieces of furniture.

0:30:170:30:19

You can change the temperature, open and close the doors,

0:30:190:30:22

change the mood, adjust the lighting, dim it, make it romantic.

0:30:220:30:26

Let's leave it bright.

0:30:260:30:27

So, whilst all of this is great for the guests,

0:30:270:30:30

it can be bit of a headache for an electrical engineer.

0:30:300:30:33

Luxury calls for a lot of energy.

0:30:350:30:38

Just the lights in one suite can draw more power

0:30:380:30:41

than all the appliances in a British home burn in a whole day.

0:30:410:30:46

And making the mood romantic could have shocking consequences.

0:30:460:30:51

So, to dim the lights, simply press a button.

0:30:510:30:54

Not complicated - we're all familiar with dimmers.

0:30:540:30:56

But simply pressing that button could have had a catastrophic effect.

0:30:560:31:01

The origin of the potential problem lies

0:31:010:31:04

in what happens to an electrical current when you dim the bulb.

0:31:040:31:08

It can heat the wires to abnormal levels and start a fire.

0:31:080:31:13

To show what can go wrong when you're adjusting the ambience,

0:31:160:31:19

we're going to check in to my own replica of a luxury hotel room.

0:31:190:31:23

I've brought electrical expert Paul Mitcheson along

0:31:300:31:35

to create a sophisticated lighting system.

0:31:350:31:37

Oh, yeah, home from home.

0:31:410:31:42

No, I'm not back in the Burj Al Arab, this is my replica.

0:31:420:31:46

There's no en suite yet or Jacuzzi or under-floor heating,

0:31:460:31:49

but it's got a bedside table and plastic roses.

0:31:490:31:52

Everything the modern luxury bedroom needs, including lights.

0:31:520:31:56

They don't really come on and off when you do that,

0:31:560:31:59

that's just Paul out there operating them.

0:31:590:32:02

Still, thank you! There it is, all working perfectly.

0:32:020:32:06

My shed may not be a fully authentic replica,

0:32:090:32:12

but it has two crucial similarities.

0:32:120:32:14

It has a high voltage power supply for the electrical systems

0:32:150:32:19

and it has a dimming system.

0:32:190:32:22

Paul, in addition to providing adult supervision,

0:32:250:32:28

has set up a high-tech monitoring station

0:32:280:32:30

complete with a complicated array of gauges and test equipment.

0:32:300:32:35

Paul, to me as a customer, staying in my luxury hotel room

0:32:350:32:39

the lights are on, that's it. What is going on in there? What's happening?

0:32:390:32:43

So, what we're doing is we have a wave form, which we can see on the oscilloscope,

0:32:430:32:47

and this is electric current which is powering the lights.

0:32:470:32:50

And at the moment, the key thing to note here is that this is a very smooth wave form.

0:32:500:32:54

So, this is what a normal current looks like on an oscilloscope.

0:32:540:32:59

It's regular and safe.

0:32:590:33:02

So, a smooth wave form there. What if I change things a bit?

0:33:020:33:05

This is what I want to change.

0:33:050:33:07

It's a luxury bedroom, but that light is a bit harsh.

0:33:070:33:10

You want something a bit more cosy?

0:33:100:33:12

Yeah, I'd like to change the light setting.

0:33:120:33:14

Instead of three on full, I'd like to put six lights on but dim.

0:33:140:33:19

OK, in that case, what we could do is, we could dim those,

0:33:190:33:23

bring up another three.

0:33:230:33:26

It's a much better ambience in there.

0:33:270:33:29

Am I right? That's the same amount of light.

0:33:290:33:33

We've just got six lights on but lower.

0:33:330:33:35

That's right. The same amount of power into the lights.

0:33:350:33:38

We can see from the oscilloscope that something has changed drastically.

0:33:380:33:42

So, what's different?

0:33:420:33:44

The problem is now that we're delivering power to the lights in short bursts.

0:33:440:33:49

So that's how the power's been halved then?

0:33:490:33:51

That's exactly right, yes.

0:33:510:33:54

Because I always thought a dimmer was like a tap,

0:33:540:33:57

cos if you turn a tap on full and then that's too much

0:33:570:33:59

you turn it down halfway and half the amount of water comes out. I thought a dimmer was the same.

0:33:590:34:04

Turn it down and half the amount of electricity goes to the lights.

0:34:040:34:08

So, it's more like turning the tap on and then off and then on and then off.

0:34:080:34:12

Modern dimmer switches basically shut off the power to the light

0:34:140:34:18

120 times a second.

0:34:180:34:20

It has the effect of not letting the light ever achieve full brightness.

0:34:200:34:25

It also has a side effect.

0:34:250:34:28

So, it's the same amount of electricity

0:34:280:34:30

but being switched on and off.

0:34:300:34:32

-Right.

-Why is that different? Why does that upset things?

0:34:320:34:35

You're only delivering the power for a short period of time.

0:34:350:34:38

And in order to that, you introduce extra heating effects in the wires.

0:34:380:34:41

An electrical current in a wire always creates

0:34:410:34:44

a certain amount of heat.

0:34:440:34:46

But adding a dimmer switch can add extra heat to the wire,

0:34:460:34:50

sometimes dangerously so.

0:34:500:34:53

The on-off action of a dimmer switch creates so-called harmonic distortion,

0:34:530:34:58

a sort of chaotic current in the wires,

0:34:580:35:01

frequencies the system isn't designed to deal with.

0:35:010:35:05

A wire heating up doesn't sound too ominous.

0:35:070:35:10

It might smoulder away but, in the wrong circumstances,

0:35:100:35:13

that wire can ignite flammable items close to it.

0:35:130:35:17

If, for example, someone had carelessly left the exposed wire

0:35:170:35:22

on a waste paper basket full of cotton wool,

0:35:220:35:25

which might happen to be soaked in nail varnish remover.

0:35:250:35:29

It could happen!

0:35:290:35:31

With six lights on dim, let's see what does happen.

0:35:360:35:40

My hotel's on fire, just so they know.

0:35:500:35:53

That's a lot of heating!

0:35:530:35:56

That took less than 20 seconds to catch.

0:35:560:35:59

You really wouldn't want that in a top-class hotel.

0:35:590:36:02

Our shed's on fire. You've ruined my hotel quite badly.

0:36:030:36:07

I see your point. That is a potential problem!

0:36:070:36:11

Cor blimey! Bloody hell.

0:36:130:36:15

Man, that's hot!

0:36:220:36:23

Obviously, this is a very exaggerated scenario.

0:36:260:36:31

Electricians don't generally run exposed wires through flammable bins of cotton wool.

0:36:310:36:37

But if it is a serious threat, how come dimmers are so common?

0:36:370:36:42

Why isn't there a fire every time someone wants to change the ambience?

0:36:420:36:46

That could ruin the mood.

0:36:460:36:47

It's because of electrical defences that include part of a camera's flash.

0:36:480:36:54

Yeah, I do see your point.

0:36:580:37:01

It's not great, is it?

0:37:010:37:02

My hotel's ruined. So clearly that needs to be avoided.

0:37:020:37:05

It is. They have dimmers and that doesn't happen.

0:37:050:37:08

So, what's the solution?

0:37:080:37:09

So, the solution is the capacitor that's in the camera flash.

0:37:090:37:13

We're all familiar with a regular camera.

0:37:130:37:17

Early camera flashes used explosive powder to create the bright light

0:37:190:37:24

but carrying that around was not for the faint-hearted.

0:37:240:37:28

They needed a safe, portable alternative.

0:37:320:37:35

And the solution came in the form of an electrical component,

0:37:380:37:42

known as a capacitor.

0:37:420:37:44

In cameras, the capacitor stores up energy

0:37:440:37:48

and releases it all at once setting off the flash.

0:37:480:37:52

But, in buildings, combined with inductors,

0:37:520:37:55

they act like filters, removing the chaotic currents that can cause fires.

0:37:550:38:01

This is a regular, relatively large capacitor.

0:38:010:38:03

So, this is the thing that allows you to take energy more slowly

0:38:030:38:08

and release it back to the lights.

0:38:080:38:11

All that does is accumulates this energy and releases it at a controllable rate.

0:38:110:38:15

And stops that happening.

0:38:150:38:17

Burning your shed down.

0:38:170:38:19

Wish I'd known that ten minutes ago, I'd still have a shed.

0:38:190:38:24

The Burj al Arab's capacitors are buried deep in the building.

0:38:240:38:28

With the inductors, they are the unsung electrical heroes

0:38:280:38:32

that protect the hotel from itself and its pampered guests.

0:38:320:38:36

I guess it is a relief to know that, when I dim the lights,

0:38:360:38:39

I'm not going to set fire to the Burj al Arab.

0:38:390:38:42

I imagine the bill would be quite big if I did.

0:38:420:38:46

I'd never get that through on expenses.

0:38:460:38:48

The designers of this amazing building

0:38:500:38:54

didn't limit the spectacle just to the structure.

0:38:540:38:57

It is, after all, a hotel.

0:38:570:39:00

And the guests will spend most of their time inside looking around,

0:39:000:39:03

not outside looking in.

0:39:030:39:06

When it comes to earning its keep,

0:39:090:39:11

this building is all about symbolising luxury and opulence

0:39:110:39:15

so what could be the best possible luxury here,

0:39:150:39:19

in a hotel perched in a scorching desert of sand and sea?

0:39:190:39:23

Yep, fountains.

0:39:250:39:28

Think about it, a fountain in the desert is the ultimate in opulence.

0:39:290:39:34

And, not just any old fountains,

0:39:340:39:37

a series of digitally-controlled million-pound masterpieces.

0:39:370:39:41

And, whilst fountains are pretty and all that,

0:39:420:39:45

it takes some surprising engineering to create the flair.

0:39:450:39:48

You need to be seen to do something extravagant

0:39:510:39:54

and opulent with the water.

0:39:540:39:56

And the water features here are an engineering feat

0:39:560:39:59

in their own right. Mesmerising.

0:39:590:40:02

Sometimes the water doesn't even look like water.

0:40:030:40:07

That's because it's not behaving like water,

0:40:110:40:14

normal water that is.

0:40:140:40:16

Normal water can't move like this does.

0:40:160:40:19

To allow it to play these tricks, you need to eliminate turbulence.

0:40:220:40:28

It has to achieve an almost unreal glassy smoothness,

0:40:280:40:31

something called laminar flow.

0:40:310:40:35

Here it comes, if you need it,

0:40:360:40:38

a quick reminder of how water behaves in a flow normally.

0:40:380:40:42

There it goes, that's...

0:40:440:40:47

Well, it's a mess, that's because of turbulence,

0:40:470:40:50

there's lots of eddies and flows and swirls in there,

0:40:500:40:52

which is fine for use here on the farm.

0:40:520:40:56

But if you want to make those beautiful polished glass-like tubes

0:40:570:41:01

in the fountains at the Burj al Arab you need to smooth that flow out.

0:41:010:41:06

You need to make it laminar.

0:41:060:41:09

And to do that engineers turned to a type of hose

0:41:090:41:12

used to help put out fires in sky scrapers.

0:41:120:41:15

The 1930s. Buildings grew taller.

0:41:170:41:22

Fire fighters needed to stream water higher to quench towering infernos.

0:41:220:41:26

A helpful hydraulic engineer realised that turbulence

0:41:260:41:30

reduced the range of fire hoses,

0:41:300:41:32

because the water flow broke up in air.

0:41:320:41:35

His invention to smooth out the flow in fire hoses,

0:41:350:41:38

to make it more laminar,

0:41:380:41:40

was the key to the Burj al Arab's glassy fountains.

0:41:400:41:43

Right, quick quiet minute before we do the next bit

0:41:430:41:46

and we'll be finding out about this laminar flow business.

0:41:460:41:49

Which is far as I understand is doing, well what seems impossible?

0:41:490:41:54

Here is an example, my coffee,

0:41:540:41:56

don't worry, they'll get a coffee too, once they've earned it.

0:41:560:42:00

If I stir in milk, there you go,

0:42:000:42:05

stir it all in, there you go, it's all mixed up thoroughly.

0:42:050:42:08

Wouldn't it be kinda cool if we could un-stir it,

0:42:080:42:12

and we would be left with a blob of milk and black coffee?

0:42:120:42:16

So maybe if I stir the other way?

0:42:160:42:19

Obviously you can't, that would be turning back time.

0:42:190:42:23

We haven't yet conquered time travel and you can't un-stir coffee

0:42:250:42:30

unless you can make water behave in a fully laminar way.

0:42:300:42:34

Amazingly, however you can un-stir some liquids.

0:42:340:42:39

Professor Tom Mullen from Manchester University,

0:42:400:42:43

an expert in fluid dynamics shows me how.

0:42:430:42:46

So Tom, with this device are we about to spin a salad

0:42:470:42:50

or do some painting and what's this got to do with laminar flow,

0:42:500:42:54

whatever that is, and trying to unstir my coffee?

0:42:540:42:57

That's your mission to explain all of that.

0:42:570:43:01

Well, what you have to do is put this colour dye into the fluid

0:43:010:43:04

and we will stir it around and see what happens.

0:43:040:43:08

The liquid inside is thick viscous sugar syrup...

0:43:100:43:13

-A bit further along here. This direction.

-Right.

0:43:130:43:16

..and the coloured blobs are the same stuff with food dye added.

0:43:160:43:21

So three blobs, good, not much flowing,

0:43:230:43:26

laminar or otherwise going on now.

0:43:260:43:28

No, we have to create the flow, so to create the flow

0:43:280:43:31

we have to turn that handle, say five times in that direction.

0:43:310:43:36

-Right, it's quite thick stuff this. One...

-Very sticky.

0:43:360:43:40

Two...

0:43:420:43:43

Keep going.

0:43:430:43:45

Three...

0:43:450:43:46

Four...

0:43:480:43:49

Five. OK, I've done that.

0:43:500:43:52

-Now, it looks like we've created a right mess.

-It's a mess. It's all gone.

0:43:520:43:56

What we need to do is go backwards, the same number of times.

0:43:560:44:00

-So I'm literally un-stirring it?

-Unstir.

0:44:000:44:03

I feel like someone might be having a laugh at my expense.

0:44:030:44:07

One...

0:44:070:44:08

Two...

0:44:100:44:12

Three...

0:44:130:44:16

-Four.

-Slow down a bit, slow, slow, slow.

0:44:180:44:25

There you have your three blobs back again.

0:44:250:44:28

Wow. Look at that! I have literally unstirred it.

0:44:280:44:32

That's a great party trick.

0:44:320:44:33

Thick, viscous liquids like sugar syrup are very smooth.

0:44:370:44:40

It's easy to make them move in a laminar way.

0:44:400:44:44

They don't behave turbulently like water.

0:44:440:44:46

So you can un-stir them and make the blobs re-appear.

0:44:460:44:50

If water behaved like that you could un-stir your coffee.

0:44:500:44:54

To make water flow in a laminar fashion, you need to remove

0:44:580:45:03

the turbulence, with a laminar flow nozzle.

0:45:030:45:06

The good news immediately is, now correct me if I'm wrong,

0:45:060:45:09

is that this appears to be laminar flow in water.

0:45:090:45:12

This is laminar flow coming out of this nozzle here,

0:45:120:45:15

whereas this is turbulent flow. The reason you can tell

0:45:150:45:18

immediately that it's turbulent is that you can see it.

0:45:180:45:22

It scatters the light and in this case it's glassy smooth and laminar.

0:45:220:45:26

Quite a simple difference really, neat tidy and elegant, and scruffy and a mess.

0:45:260:45:30

But to achieve this it needs this device here,

0:45:300:45:33

-that looks like something from a '60s sci-fi movie, what is it?

-You have turbulent flow coming in

0:45:330:45:41

and you have the flow goes through these gauzes and these straws and so the turbulence decays as it comes

0:45:410:45:46

through here and you end up with laminar flow coming out of the nozzle.

0:45:460:45:51

The gauze and straws effectively smooth the water,

0:45:510:45:54

removing the bubbles and swirls that cause turbulence.

0:45:540:45:58

Non-turbulent water can flow quicker and more smoothly.

0:45:580:46:03

So to solve the problem then of fast moving laminar flow in water

0:46:030:46:06

for the Burj al Arab's fountains, what you need is a device like this.

0:46:060:46:10

-To calm the water down.

-Yes.

0:46:100:46:13

And smoothly flowing water also helped fire fighters.

0:46:140:46:19

In the '30s, American engineer Horace Barker had a brainwave.

0:46:210:46:24

He realised that removing turbulence made the water travel further.

0:46:240:46:29

His new fire hose design had metal feathers inside

0:46:290:46:33

that aligned the water as it left, reducing this turbulence.

0:46:330:46:36

Barker's flow-straightener extended the range of fire hoses.

0:46:380:46:41

The smooth water flow travelled further.

0:46:430:46:45

So fire-fighters could tackle blazes on the higher floors

0:46:450:46:48

of sky scrapers more easily.

0:46:480:46:50

Laminar flow nozzles go one step further than Barker's device,

0:46:510:46:55

removing all turbulence

0:46:550:46:56

and smoothing the water to a glassy finish.

0:46:560:46:59

The fountains at the Burj al Arab incorporate 66 laminar flow nozzles,

0:47:040:47:08

I'm pretty sure theirs aren't made from drinking straws though.

0:47:080:47:13

Either way, they allow for breathtaking displays.

0:47:130:47:15

You see, the crucial thing about the Burj al Arab is that

0:47:170:47:20

it's all about the bling. It's engineering to impress...

0:47:200:47:25

not just to survive.

0:47:250:47:28

All these engineering achievements have made

0:47:280:47:31

the Burj al Arab a spectacular feature on Dubai's skyline.

0:47:310:47:35

The Burj al Arab instantly joined the world's list

0:47:370:47:39

of iconic landmarks. Becoming the face of Dubai.

0:47:390:47:42

Synonymous with it's re-invention as a luxury playground.

0:47:420:47:49

Behind the glitz, the glamour and the spectacular show,

0:47:550:47:59

there is some amazing, and solid engineering.

0:47:590:48:03

And none of it would have been possible without...

0:48:050:48:08

..a game of jacks...

0:48:080:48:09

..an engine cam...

0:48:110:48:14

..the pages of a phone book...

0:48:140:48:17

..a revolution in fire-hose design...

0:48:190:48:21

..and a camera flash.

0:48:210:48:25

-You've ruined my hotel, man!

-THEY LAUGH

0:48:250:48:29

Subtitles by Red Bee Media Ltd

0:48:360:48:39

Email [email protected]

0:48:390:48:42

Richard Hammond checks out the world's tallest and most distinctively shaped hotel, the 320-metre-high Burj Al Arab, or Arabian Tower. Rising from its own custom-built island, 300 metres off-shore, the sail-shaped building has already become one of the world's most recognisable buildings, and an icon for Dubai.

Constructing the island was the first engineering challenge. Protecting it from two-metre-high waves called for strong sea defences. Richard demonstrates the power of quite small waves by explosively releasing a ton of water just two metres above a coffee table. His second coffee table relies on a furniture protection system inspired by the Burj's sea defences. Tyres lashed together create spaces that absorb the destructive energy of the 'wave'.

Building in the extreme heat of the desert posed construction challenges due to steel expansion. The 85-metre steel trusses forming the hotel's exoskeleton were fitted together thanks to an ingenious solution inspired by an engine cam, a rotating mechanism which presses down on valves by moving eccentrically or off-centre. Clever rotating fixings were used, which allowed builders to move the fixing pin off-centre until the two holes married.

The Burj Al Arab is a high-tech palace: remote controls operate lights, doors, curtains, and climate control. Richard creates his own luxury hotel room, with a sophisticated lighting system, and watches it all go up in flames simply because of what dimmers do to the electrical current. The solution lies in a capacitor - the electrical component used to fire a camera flash.

Finally Richard reveals how the secret of the Burj's extraordinary and unnaturally glassy water fountains - achieved thanks to laminar flow - and a revolutionary fire hose.