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Practice English Speaking&Listening with: Track Test: Nissan DeltaWing Driven At Road Atlanta -- /CHRIS HARRIS ON CARS

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CHRIS HARRIS: A few years ago, a very clever Englishman

called Ben had an idea for a racing car.

It was to answer a specific criticism with modern racing

about downforce.

Because modern racing cars have to have downforce,

particularly sports cars, to go around corners quickly at

high speed.

That's part of the sport.

But they create so much turbulence that they become

quite inefficient in going through the air, and they're

very difficult to over take each other, because there's so

much turbulent air coming off the back.

He creates something called the DeltaWing.

The problem is, there was no where to race the car.

It wasn't eligible for any championships.

And then a very brave car manufacturer called Nissan

came along and said, we can do something with this.

This is too cool not to have a part to play in our global

motor sport ambitions.

The rest is history.

They went to Le Mans where the car was doing really well

until it got punted off by an LMP2 car, and two days ago at

Road Atlanta it came fifth overall in petit Le Mans,

which is really, really cool.

And now we're going to get the chance to drive it.

[MUSIC PLAYING]

There's a problem with the seat, because I'm a big

chunkier than their normal drivers.

So they're going to go to tubby spec now.

[MUSIC PLAYING]

[INAUDIBLE]

[CAR ENGINE ROARING]

[CAR ENGINE REVVING]

[CAR ENGINE]

That's not like anything I've driven before.

Quite a lot of power--

very interesting.

Ben, this is a magnificent machine.

I've had one go in it, and done about five laps.

Everything in my head tells me that having looked at the

front of the car, it shouldn't work.

For the first time we might have a look underneath it.

And then you can tell me why you say it's physics and

science that makes it work, and I think it's some kind of

hex or maybe it's snake oil.

I don't know what it is, but it shouldn't

work, but it does.

BEN BOWLBY: It is counter-intuitive.

So, I will explain how it works.

CHRIS HARRIS: OK, well let's have the cover off it, and

we'll see what it actually looks like underneath.

You did say, earlier, you said, "Did you look underneath

the front of the car before you drove it, because if you

look underneath it, you won't want to drive it.

BEN BOWLBY: That's true, because the tires are 100

millimeters wide.

I mean, they are the size of a dish of eggs.

It's extraordinary--

same diameter, same width.

And the wishbones--

because the loads are so small, because the whole front

end of the car is so light, the gauge of

the steel is minute.

I mean, it's less than a millimeter thick.

So we've got incredibly, spindly, light little pieces.

Your steering arms--

these are titanium and a millimeter and a half--

CHRIS HARRIS: I'm not sure I want to look at this.

I mean, look at the spring!

So can you tell me what vehicle this spring and damper

unit assembly comes from?

BEN BOWLBY: Well, it's practically mountain bike.

I have to tell you.

CHRIS HARRIS: Sorry, can we get that?

It's a mountain bike.

Did you get that?

It's a mountain bike.

So I'm going to test you.

This is the biggest test you've ever had.

If you thought designing the car was difficult, explain to

a moderately educated car fan audience how

the hell that works.

BEN BOWLBY: Well it works, because the amount of weight

that is carried by the front axle, and the distribution of

the downforce that's made under the car on the front

axle and the tire capacity, are all actually in harmony.

They're all matched.

So the specific contact patch load, the stress at the front,

is the same as the stress at the back.

So it's like an aircraft--

it's a 2D lift and weight has to balance.

In our case, we have a third dimension, which is the tire.

So our negative lift, our mass distribution, and our tire

distribution, in terms of the capacity of the

tires, is all balanced.

And that's why it goes around the corner.

CHRIS HARRIS: And it has a very interesting steering

behavior, doesn't it, in the faster turns you're talking

about, in terms of the aerodynamic load verses the

grip that you're generating for the front of the car,

because of this narrow set up at the front.

It behaves completely differently.

BEN BOWLBY: It does tend to behave very differently.

And in fact, the tires are used much more efficiently,

because they're very close together.

And typically, on a rear engine, rear wheel drive, rear

weight bias car, the inside front tire is almost doing no

work through the corner.

So one tire is doing almost all the work.

Whereas in our case, because all of the roll stiffness

being at the rear, those two front tires see the same load

all the time.

And because they're really close to the center line,

instead of it feeling like you've got the brakes on the

one tire that's working, that kind of gives an under steer,

when it's trying to give you turning through the corner, we

don't have that problem.

Because the scrub drag, as it's called, of the front

tires acts directly, straight back on the center of gravity.

Say all of the tire's effort goes into turning the car

around the corner, rather than some of it-- the drag

element-- being an under steer moment.

So it's all to do with forces and balances and moments.

And that's what makes the car go around the corner.

When you see this rear suspension, that

will freak you out.

CHRIS HARRIS: OK, let's have a look at the

rear suspension then.

Oh dear God!

Right, OK.

BEN BOWLBY: So there are two conventional dampers with

springs on them, here.

CHRIS HARRIS: Yeah.

BEN BOWLBY: But it's how they're connected up that's a

bit peculiar.

So we have push rods from the wheels.

CHRIS HARRIS: Yeah.

BEN BOWLBY: And that's sort of, fairly understand.

This is the pivot point here.

CHRIS HARRIS: Yep.

BEN BOWLBY: So when the push rods, when the car is being

pushed down, to push rods come in this way, and they put on

these pull rods.

And you're thinking, why on earth do we to go through all

this monkey motion.

But back here, we have a beam that amplifies the amount of

damper displacement in roll compared to in heave.

And that's very important, because all of the damping for

the car in roll is done by the rear end of the car.

So if we weren't careful, we would land up with a car that

had inadequate damping in roll.

CHRIS HARRIS: Yep.

BEN BOWLBY: And say we want to give it

optimum damping in heave.

But in order to get enough in roll, we have to over drive

the dampers when there is the roll moment.

CHRIS HARRIS: All right.

BEN BOWLBY: And so this allows us to do that by the ratio

from this-- so this is the axis of rotation for the beam.

It's also the anti-roll bar.

CHRIS HARRIS: And what's the gearing effect on it?

BEN BOWLBY: So this is about 1.2 times as fast.

And obviously because of velocity, velocity squared,

you have to square 1.2 for the damper force

that you get off it.

So it's quite heavily damped in roll, because it has to do

all the work that normally halfway would have been done

by the front end.

CHRIS HARRIS: Yeah.

BEN BOWLBY: And we don't have a front end

that's rolling around.

So we've got this feel.

And I don't know if you felt when you were driving the car

that the rear felt very flat and stable.

It never felt like it kind of lurched.

CHRIS HARRIS: No, it doesn't at all.

BEN BOWLBY: There was no delay in taking load.

And you still had best part of 20 millimeters of roll

occurring, but you didn't feel it, because it

was very well damped.

And so we went through this rather elegant, but kind of

monkey motion, layout to enable us to have, in a very

passive and simple way, more damping in roll than in heave.

CHRIS HARRIS: And what's the spring rate?

Because it's quite an open wound spring there.

BEN BOWLBY: It's an 850 pounds per inch spring.

And we actually went up here compared to Le Mans.

In Le Mans we ran a 750, but the loads at this

track are so obscene.

This track is crazy high loads.

CHRIS HARRIS: Yeah.

BEN BOWLBY: And it's nearly 4G through turn one

when you're on it.

And so we actually had to support the car a bit more.

CHRIS HARRIS: I'm sorry.

I'm going to have to say thank you there, because I could

listen to that all day long.

But we'd have to have a 50 minute episode that isn't

[INAUDIBLE].

But mate, it's extraordinary.

And clearly it still excites you.

BEN BOWLBY: It does!

It really does excite me, because it is unexpected.

And we keep discovering that it has-- you know at first,

one of the things we hadn't realized was that the car was

going to be stable under brakes.

And you still think that it's got awful lot of

breaking at the rear.

It has to, because they've got bigger tires at the back.

How's that going to feel?

Well it's like launching a parachute behind you.

That's a good idea.

CHRIS HARRIS: Yeah.

BEN BOWLBY: If you try and launch a

parachute in front of you--

and that is one of the unique aspects of this car.

The parachute launched in front would

try and the car around.

But every racing car that we raced against on Saturday has

more total braking force occurring at the front axle.

So if you lock a rear, it's going around.

This car, if the guy's pushed a little hard and locked a

rear, it didn't really matter.

They could still make the corner.

It just locked it up a little bit.

Very, very different set of circumstances that make a car

that has fundamental stability, and--

CHRIS HARRIS: I think it's fantastic.

I really do-- privilege to drive it.

Thank you.

The Description of Track Test: Nissan DeltaWing Driven At Road Atlanta -- /CHRIS HARRIS ON CARS