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Watch Tom Scott England NBLA, Season 1 Episode 31 on Dailymotion (2026).
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00:00There's a door, near London Bridge,
00:02above which is carved, facts, not opinions.
00:05And inside that building is the Kirkcaldy Testing Works,
00:09and a machine that breaks things.
00:14Hello, hello, lovely to meet you at last.
00:16David Kirkcaldy.
00:17I am pronouncing that right, by the way, I double-checked with them.
00:19The town is Kirkcaldy, but the name here is David Kirkcaldy.
00:23He was a Scottish engineer, and in the Industrial Revolution,
00:26as new materials like steel were being made and forged,
00:29someone had to catalogue their properties and to prove
00:32that the companies making those materials weren't lying about
00:35how much weight and strain they could take.
00:37And so Kirkcaldy set up his testing works in what was once the County of Surrey,
00:42and is now just London.
00:44His slogan was facts, not opinions, and in 1865,
00:48the colossal universal testing machine that he'd commissioned arrived.
00:53We will work up to that, because the testing works has many machines
00:56for fact-finding, some more violent than others.
00:59Before we get to the big machine, we're going to demonstrate some other ways
01:02to dramatically bend and break things.
01:05Righto.
01:05It's what we call a Charpy impact machine.
01:08Impact it hits a sample and either breaks it or bends it.
01:13And Charpy after the man who designed it.
01:15Oh!
01:16Right.
01:17I thought there might be some fancy...
01:18No, it's just his name.
01:19No, it's just a mouse name.
01:21And we believe this is the second oldest Charpy machine in existence.
01:25Oh!
01:25And still in working order, so we'll do an impact and show you how it works.
01:29These days there are fancy electronic strain gauges,
01:32or things called polariscopes, to see stress inside transparent plastics and glass.
01:37But modern Charpy machines still do exist, and they still use the very simple technique
01:42of swinging a big hammer very precisely.
01:45This one came from a research lab somewhere.
01:47I set up a close-up camera, and Bill, one of the volunteers, lifted the pendulum.
01:52We have the sample supported on its anvils.
01:55Yep.
01:55We've lifted the weight.
01:57We're going to swing the weight down, and we will see what happens.
02:00So what is the metal there?
02:02It's hot rolled mild steel.
02:04Hot rolled mild steel.
02:06Okay.
02:07Mild steel has low carbon content.
02:09And hot rolled means it was shaped with rollers while very hot,
02:13so it's a bit more malleable.
02:14For this test, the steel should bend, but not break.
02:18And then I'll put another sample in which we've cooled down,
02:21and we'll see how they compare.
02:23What's the point of the black bar just there?
02:25This one?
02:26Yes.
02:27It's supposed to act as a break on the hammer.
02:31It doesn't break terribly well.
02:32Okay.
02:34Why would you need a break on it?
02:35As a safety thing, or to just...?
02:37You will find out when the hammer swings through.
02:38Oh, yeah, yeah!
02:40When you're ready.
02:41Go for it.
02:44It's a very simple idea.
02:46Secure thing in machine, hit thing with hammer.
02:49The key is that the hit is precise and repeatable.
02:52Looks like that.
02:54May I?
02:55Of course.
02:56You take it with you.
02:57Look, we've got masses of them.
02:59Of course you have, because you're doing this demo regularly.
03:02Yeah, that's right.
03:03Nearly broken, but not quite.
03:04Well, I'll show you something different.
03:07Look, what I'm going to do now is to put a cold test piece in.
03:10The other sample was identical, except it had been stored in dry ice for a few hours,
03:15so it was somewhere around minus 80 Celsius all the way through.
03:19Frost formed on it, as Bill put it in the machine, and, of course,
03:21I asked if I could pull the switch.
03:23All right.
03:24Whack that with your hand.
03:25I just wiped that with my hand.
03:26That's it.
03:27Ha, ha, ha, ha, ha, I'm not brave enough.
03:31Oh!
03:33It's it.
03:34And now I see why you've got the brake.
03:36Yes.
03:38Exactly.
03:39That's a terrifying machine.
03:42How heavy is that hammer?
03:44Oh, 22.5 kilodons.
03:4522 kilo hammer.
03:46And the sample is shattered, clearly.
03:49Yes.
03:50It's snapped neatly into.
03:52It hadn't shattered, it had snapped.
03:55Once it had warmed up and the frost had melted, it looked like this,
03:58the internal structure revealed.
04:00That seems obvious, but when steel was a new material, that had to be discovered.
04:05There's a classic example of steel going brittle at low temperature,
04:09and that's SS Schenectady.
04:10The SS Schenectady was an oil tanker built of steel,
04:14mass-produced in just a few months during the Second World War.
04:17The production rate was fantastic, but they were fairly brittle ships,
04:20and this thing was taken out on test, accepted as OK,
04:25moored up overnight in cold water.
04:26Oh.
04:27Bang.
04:28Two half-ships.
04:30Wow.
04:31I thought Bill was simplifying for a joke there, but no,
04:34I looked up the SS Schenectady, and while the cause was a bit more complicated
04:38than just the wrong steel, it did, very literally, snap in two.
04:42So they ended up using a more sophisticated steel, a more expensive steel,
04:47but, you know, when you're breaking ships that cost $2.3 million in half,
04:51you can spare a bit for a bit of quality metal.
04:54On to the next machine, demonstrated by volunteer Julian.
04:57We've looked at Sharpie samples downstairs, that's toughness in terms of impact.
05:02These machines do toughness in terms of indentation, how hard the surface is.
05:08So if you're doing a bearing, you want to know how hard the sideways thrust's going to be.
05:13If you're putting down floor, how hard's the floor?
05:15In a restaurant, you need to know how hard it is.
05:18So these machines do that.
05:19That particular machine is from about 1920, and it was in regular use at the testing works
05:24until they closed in 1974.
05:26Which feels surprisingly recent, right?
05:29Any time I've heard about the testing works, it's all Victorian engineering
05:32and the Industrial Revolution.
05:34But this continued basically until modern computer simulation
05:37and electronic techniques came along.
05:39It's a charity now, by the way, and they did ask me to mention
05:41that they're looking for volunteers.
05:43As for this machine, with apologies to Julian, who gave a great demonstration,
05:48I am going to skip over the details because, unfortunately, it is not particularly visual.
05:53So there's some weights hanging on it.
05:55These are the weights.
05:56And then that's going to get multiplied by the hydraulics in there.
06:00Yes.
06:02Which we pump up, pressure's coming up, the weights pop up,
06:05so the weights are now acting down onto our sample.
06:10The result is a small dent, which you measure,
06:12and that gives you a Brinnell hardness number.
06:15There was also the Vickers machine, which uses a diamond tip for harder surfaces,
06:19and which is, alas, just as underwhelming on camera.
06:23Yep, just push release.
06:25You've done a test.
06:27Hey!
06:28Somewhat more dramatic was the Avery machine,
06:31originally used for testing parachute cord and other fabrics,
06:34which Jonathan demonstrated using a packing strap.
06:37Can you do that one-handed and start turning anti-clockwise?
06:42I feel like I should be wearing safety glasses here.
06:44Oh, yes, yes.
06:45Hold on.
06:46We'll give you the works.
06:48Here we are.
06:49Safety glasses.
06:50Thank you.
06:50Hard hat.
06:51Oh, I think I can deal without the hard hat.
06:53Oh, no, come on.
06:55This is an old British Telecom logo from the 1970s.
07:00This is a pre-privatisation British Telecom hard hat.
07:04Yeah, yeah.
07:05Right, now you're safe.
07:07Good, right.
07:08I should not have complained about not having eye protection.
07:11The hard hat did not stay on, but I did keep the goggles.
07:14As I turned the wheel, the weight on the back swung outwards,
07:17the strain increased on the packing strap.
07:21F minor, I think.
07:22And eventually it got to breaking point.
07:25Listen to that.
07:29I mean, you can just hear the creaking over the road noise.
07:32May I?
07:32Yes, keep going.
07:35Oh, that requires a lot more force,
07:37which I know is an obvious thing to say.
07:39Yes, indeed.
07:40Oh!
07:44Now, that didn't immediately release the weight.
07:47There's the ratchet.
07:49Which stops it swinging back.
07:51So that broke at 141.5 pounds.
07:57All of which brings us to Kirkcaldy's universal testing machine.
08:01It occupies the entire ground floor of the building.
08:04It's 15 metres long, weighs more than 100 tons,
08:06and it's hydraulic.
08:07It uses water pressure.
08:09These days there's an electric pump for that,
08:11but in the past it was served by the London Hydraulic Power Company,
08:15who had a distribution network for ultra-high-pressure water
08:18across the centre of London.
08:19Water was centrally pumped by steam engines and later electric pumps
08:23and arrived at the customers at about 25 times the pressure
08:27that comes out of a modern domestic tap.
08:29If you imagine a fire hose,
08:30that water arrived at about twice the pressure
08:33that would break a fire hose.
08:36That could be used to power lifts and cranes,
08:38machinery and workshops, revolving stages in theatres.
08:41In the basement, the museum has a piece of the old pipe work.
08:44See how thick the walls are?
08:45Yeah. So that was…
08:47That was a bit of the London Hydraulic Power Company's pipe.
08:54Because they weren't sending much water.
08:56They were just sending very high-pressure water.
08:59You didn't need to pull an entire city's showers and baths and everything.
09:03It was just for industry.
09:05It was just for industry.
09:06Yeah. It's astonishing.
09:08Why have your own steam engine or heavy machinery,
09:10when you can just pay someone else to run it and maintain it,
09:13connect to their pipe network and use their water pressure?
09:16But even that colossal pressure wasn't enough for the universal testing machine.
09:22Jane showed me the old hydraulic intensifier.
09:25And this intensifier is capable, was capable, but it doesn't work anymore, thank God.
09:33I was about to ask whether that was a good or a bad thing.
09:36That's an enormous insurance risk waiting to happen.
09:39Yes, indeed. It could step the pressure up to 4,500 PSR.
09:48In metric, that's 310 bar pressure.
09:52A water jet at that pressure is enough to slice through flesh.
09:56They still used the intensifier at the testing works until the 1970s.
10:00We know that because we had a visitor who worked here at the time.
10:05And he said, oh yeah, I recognise that.
10:09I got that working again. And he told us how he did it.
10:13And they used it to drive the big machine when they were testing the rebar
10:20for the rebuilt London Bridge. And he said, I did that.
10:24The testing works closed in 1974. Some of the technology is Victorian,
10:28but it was useful for a long time. And by the way,
10:31the London Hydraulic Power Company kept going until 1977.
10:35After they finally stopped transmitting water,
10:37they were bought by a telecoms company who put fibre optics through their old pipes.
10:41Anyway, after all that, let's go see the machine.
10:44So, it looks horrendously complicated, but in fact,
10:50you can split the machine into two parts.
10:53So, this side of the machine is the bit that exerts the force on the sample.
11:02And we've got our sample already in place.
11:05That sample was, again, a mild steel bar, just a lot bigger,
11:09and with chalk marks on it, so any movement could be tracked.
11:12And there would definitely be movement.
11:14And if we walk right down to the end of the room, we can see the driving force,
11:22which is this cylinder here. Inside the cylinder is a ram.
11:28You can see the ram poking out at the top here.
11:32And when water is driven into the cylinder under pressure,
11:39it forces the ram out of the cylinder towards the back end of the room.
11:46So, as the water pressure increases, those hydraulic rams pull away,
11:50or at least they try to.
11:52So, if we walk further,
11:55at this point, the rods are moving that way.
12:00You've got props!
12:01I've got props!
12:02Thank you, Julian.
12:04Right.
12:04So, everything is moving in that direction.
12:08And these are screws here?
12:09They are turned rods.
12:11And the reason that they are turned is, if we move a little further up,
12:22this is the movable carriage,
12:26which by turning these wheels here, you can move up and down the turn rods to accommodate different sized samples.
12:35Oh, so you could handle a little sample like we've got in there today,
12:39but you could also have an enormous steel I-beam in here.
12:43Exactly.
12:44It goes for what?
12:45Exactly.
12:46Five meters?
12:47Four, five meters?
12:48Six meters?
12:48Yeah.
12:49Yeah.
12:49And that was really, really important at the time the machine was built,
12:55because the overall integrity of the thing that you're testing depends not only on the material that you've chosen,
13:06but also the quality of the manufacturing process, the two combine.
13:12And at the time, the manufacturing processes were nowhere near as refined as they are today.
13:22So, you had to test the whole thing.
13:25So, you might, you know, a column like that, or exactly, you had to.
13:30Yeah, you might just literally put one of these in the machine.
13:33Exactly, exactly.
13:34And the machine is capable, was capable, still is with the right tooling, of testing things in tension,
13:43which is what we're going to be doing today, compression.
13:47If you wanted to test things in compression, you'd have to mount them between the movable carriage and there.
13:57It could do bending, it could do torsion, and it could do bulging and thrusting, whatever they were.
14:06I don't know.
14:06All through various adaptations.
14:09All through various adding extra bits of tooling to the machine to do that.
14:14All that force from the water pressure pulls on the sample,
14:17which becomes the only meaningful connection between the hydraulic rams
14:20and the other side of the machine called the steel yard.
14:23Yes, there'll be a little friction from the wheels that it all sits on and the floor and such,
14:27but the only relevant connection is that one sample.
14:31So, everything's going that way.
14:34That's being stressed, it's being pulled.
14:39Right at the top here, there is a pivot, which I believe is called a knife-edge pivot.
14:47And the effect of that, as that's being pulled that way, the effect of that is to cause this arm
14:57here to swing out in that direction.
15:03And you can see the connection here is to these two bars at the bottom.
15:13So, yep, the pivot is swinging out, those bars are being pulled that way.
15:18And it's taking the bars with them.
15:20Those bars are connected to the operator's console, where Colin would be standing in a couple of minutes.
15:25In here is what I believe is called a bell crank.
15:30So, this bar, or these bars, are attached to the bottom of the bell crank.
15:38And, of course, that moves in that direction, causing this bit here to get out of balance.
15:49So, that now starts moving up.
15:51Okay.
15:53Yes.
15:54Just about.
15:55Okay.
15:55So, look, these bars are moving that way.
15:58Yeah.
15:59There is a bell crank in there.
16:03So, as those move right, that, again, starts to pivot up and it all falls out of balance.
16:08Yes, you've got it.
16:10Let's put another arrow on there.
16:12But you can't see that, it's inside there.
16:15Yep.
16:15The operator has two jobs.
16:16First, to regulate the water flow and the power in the machine,
16:19so the pressure is applied steadily and gently to the sample.
16:21And the second is to keep the machine in balance, to stop that bar pivoting up,
16:26so the measurement can be taken.
16:27As this comes out of balance, you can bring it back into balance by moving the weight.
16:37Oh, 350 pounds of weights down there.
16:39Correct.
16:41Yes.
16:42How do you know that it's in balance?
16:44Well, for this huge machine, it all comes down to a pointer on here and a scratch mark on the
16:56machine.
16:56So, if those are lined up, then you know how much force is being applied from these weights to bring
17:06it back into balance.
17:07Yes.
17:08To stop it pivoting any further.
17:10Yes.
17:11Which gives you the reading on that.
17:14Correct.
17:14If you're confused by the description of the machine, don't worry, so was I.
17:18I tried to recap it in one go.
17:20The operator here has two jobs.
17:23Number one is to run these two valves here, which put water into the cylinders.
17:29And also, I just like this, do not open these two lower valves, they flood the basement.
17:34Okay, the top two valves control water into the cylinder over there.
17:38Yes.
17:39The water pressure over there is pushing the enormous rods here that way.
17:45Yes.
17:46That puts tension on the sample just here, which is the only relevant link between the two sides of the
17:53machine.
17:53Yep.
17:55That sample then puts tension onto the pivot just here.
18:01Yeah.
18:01The pivot translates that into movement that goes that way.
18:05Yep.
18:06That pulls these rods this way.
18:10Yep.
18:10That, in turn, means that you can keep the machine in balance by moving these weights.
18:15That lets you measure how much force is being applied.
18:18And at some point, that's going to break, and at that point,
18:21you very rapidly start turning the dials.
18:23But it doesn't matter that the sample is broken.
18:28That's why you've got the separation between the two sides,
18:30because the weights are now in position.
18:33Yeah.
18:33Locked off.
18:34Yes.
18:34You know where that broke.
18:35Yes.
18:35Doesn't matter anymore.
18:36Yeah.
18:37Yeah.
18:37Yeah.
18:38That's so clever.
18:39So simple.
18:42To get the final load, there's a scale on here, right?
18:48Yep.
18:48And what you do when you're finished, you take the reading on the scale,
18:54multiply that by whatever you've got on the weight holder, and you're done.
19:01Let's break that sample.
19:03The universal testing machine wouldn't always be used to break things.
19:06If you just needed to prove that some iron or steel could withstand a particular force,
19:10then you probably wouldn't test it much past that force,
19:13because clean-up's going to be a nightmare.
19:14Now, this wasn't about destruction unless it had to be.
19:18It was about facts, not opinions.
19:20The maximum load the machine could provide was more than 450 tons.
19:24Imagine ten fully loaded cargo trucks, all tied on and dangling from one sample.
19:30Colin turned the valves, and the cylinders started to pressurise.
19:34So your job now is to keep this in balance?
19:36Yes, you're trying to...
19:37You send the weights this way.
19:39Yes.
19:40That's going to start bringing that back down.
19:41A little bit now.
19:42And it's going to get pulled up as that...
19:44Yes.
19:45...imperceptibly moves that way.
19:47Right.
19:50100...
19:50PSI, pounds per square inch is being called out by my colleague.
19:54And that's the pressure on...
19:56Yes, the pressure on the cylinder.
20:00I don't know where to look.
20:02It was this weird contradiction, a delicate balancing act,
20:06keeping the two sides working together while ever-increasing force,
20:09tons and tons of force was being applied.
20:12And I expected the steel sample to break.
20:15I expected it to do nothing for a long time and then bang.
20:18What I did not expect is for steel, industrial steel, to stretch.
20:23Can I see that expanding now?
20:28What?
20:29I feel like I can see it being stretched now, like taffy.
20:35I can see that.
20:38That's...
20:39Oh!
20:39There you go.
20:42The most incredible thing was something I only noticed looking at the edit.
20:46I didn't see it at the time.
20:47I must have flinched or missed it or just not understood that it could happen.
20:51The chalk markings exploded off the steel.
20:55And the answer?
20:56So 119 on the scale.
20:58Yes.
20:59350 pounds down there.
21:0341,650 pounds.
21:05Of force required to break that steel sample.
21:08That is just under 19 tons.
21:11So if you want to test a sample like that, you can somehow rig up 10 modern cars,
21:16tie them together and dangle them from a single piece of steel.
21:19Or you could use Kirkcaldy's testing machine.
21:23What a machine!
21:24Right, so there you have it.
21:25Thank you, folks!
21:26Wow!
21:28Next time, I step inside a secure facility and see how the lights are kept on around Britain.
21:33Clhet dividers are in their hand.
21:33It does not matter.
21:33No.
21:33That's really not me?
21:34And that's fine.
21:34– Sous-titrage FR 2021