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[CAR ENGINES]
CHRIS HARRIS: A few weeks back, I did a race with Andy
Green in the Dunlap Radical UK Cup.
We shared a car for two 40-minute
races at Brands Hatch.
Now, if you don't know who Andy Green is, you should.
He's the holder of the world land speed record at 763.035
miles per hour.
And soon he will drive Bloodhound SSC, a machine that
aims to top 1,000 miles per hour still
connected to the ground.
He's basically a hero.
And he used to fly fast jets for the RAF.
The race weekend was a chance for Andy to see how a small
race car with wings and slicks would help his training, and
for me to pepper him with irritating questions like,
ooh, does it feel really fast going 700 miles per hour?
Well, this is a kind of video blog vlog pastiche, collection
of stuff, whatever you want to call it, from the weekend.
And for starters, here's Andy.
ANDY GREEN: The thing probably that surprises most people
about straightline racing world's land speed record is
that cars, the faster they go, like any track car, the
lateral corner or lateral grip tire cornering stiffness,
whatever you want to call it, goes down.
And the faster you go, the less grip you've got sideways.
If you're going to extreme speeds, 400, 500, 600, 700,
800 miles an hour, then the car is sliding pretty much
continuously at that stage.
The wheels are planing on a dry lake bed.
The vehicle is moving around in the
slightest of cross winds.
Having more paint on one side of the car than the other will
produce a side force.
There are so many things that will move the car around.
And experiencing that for the first time at 600 or 700 miles
an hour is inevitable if you're
driving a brand-new car.
Experiencing the sensations of having a car sliding around
underneath you and, first of all, not panicking, second of
all, working out whether it's OK and that's normal, so
you're somewhere near your stability limit where you're
actually nice and comfortable, or you're over your stability
and the car is starting to get away from you, and what you
can do about it.
And then, because you haven't panicked, putting in the right
amount of steering correction or backing off on the power a
little bit--
all of that decision-making process, I don't have the time
to practice at 600 or 700 miles an hour.
Coming here to a racetrack and practice going around in
circles and scaring myself at 100 miles an hour and getting
used to a car that's moving around, recognizing whether
I've got a bit more to push, whether I've slightly
overcooked it and I need to start doing something to
collect the car, that same principle and the same mental
process and the same psychological getting used to
being a little bit scared but not too scared and being right
on the top of the stress performance curve, that's a
brilliant thing to practice for the weekend.
And as you and I are both discovering, the Radical is a
great car to practice it in, because it is quick.
Its handling does change with speed
because of the aero package.
And that actually is quite useful for me.
I haven't done that before.
And it's relatively forgiving.
We've both been backwards down the main straight.
That wasn't intentional for either of us.
But we've both learned quite lot about it.
And the car's forgiving enough that it's out there now, ready
for the race.
CHRIS HARRIS: So the race [INAUDIBLE] was a pretty
normal setup--
test Friday, qualify Saturday morning, race Saturday
afternoon and Sunday.
This is the car we were racing, a Radical SR3, which
to me is the classic Radical--
a tweaked Suzuki Hayabusa motor taken out to 1,500 cc.
That's 210 horsepower and 130 foot-pounds of torque.
The car weighs just 570 kilograms.
And as you can see, it has a [BLEEP]
load of aero.
It has a paddle shift gearbox, and it runs Dunlop SLICKS.
The challenge with a Radical is
getting used to the downforce.
Even compared to a fast GT car, the turning and cornering
speeds are breathtaking.
And you have to take a leap of faith to find
the limits of grip.
The braking performance is startling, too.
It only has little 260 millimeter steel rotors, but
it'll pull 2 Gs on the brakes all day long.
From a very high speed, you also have some aero effect,
which allows you to use big initial pedal pressures, but
not that big, as you'll see later.
Friday was a chance to get comfortable in the car, or as
comfortable as two people sharing a drive who are about
8 inches apart in height can be.
You see, I was wedged forward with a load of foam.
Brands Indy is an evil circuit.
Andy worked his way into the car.
I did the same.
In the last session, I pushed harder in the braking zone
into paddock, because that's where I was losing time.
I found some time, but sadly I lost the car.
Now, Radical were understandably miffed at me
wrecking the rear end of the beautiful
Bloodhound liveried SR3.
They went and found more stickers for the next
morning's qualifying session.
I went to look at the data.
Too much brake pressure, plain and simple.
Didn't feel like it from the inside, but the
numbers don't lie.
The rears locked, and my neck got stretched.
This seemed like a good time to ask Andy what it's like to
go really fast.
I just find this stuff mind-bending.
You had opposite lock at how fast?
ANDY GREEN: Between 600 and 650 miles an hour.
CHRIS HARRIS: How much lock did you have to apply?
ANDY GREEN: Well, the steering for the car is about twice the
ratio of a road car.
So you get about half the wheel response.
So for a normal road car if you've got 90 degrees of lock
on, you get about 6 degrees at the rear wheels.
We had a 30-to-1.
So 90 degrees of lock, which is what I had on at 600 miles
an hour, is about 3 degrees at the rear wheels.
And we're rear wheel steering.
That is part of the problem.
The twin jet supersonic car we built last time had so much
jet and structure at the front, there was no room for
the steering gear, just enough room for the wheels.
So the wheels were behind me.
So every time you put in the steering input, the car moves
the wrong way before it starts to go, which is quite
confusing for a simple brain like mine at
600 miles an hour.
And to add to that, aerodynamically the car became
unstable in the transonic region--
not uncontrollable.
And the difference is, in a push bike at slow speed, you
can actually ride a push bike.
If you let go of the handlebars, it falls over.
It's controllable, but it's not stable.
Multiply that up to 600 miles an hour, and I have much the
same problem of fighting the car.
And it's set off sideways, usually left because of the
aerodynamics.
And I ended up putting 90 degrees of lock on and backing
off on the power to just try and change the front rear
balance a little bit, get the weight off the front so that
we finished up with a better balanced car.
Soon as it started responding to the steering--
because we've got about probably two or three degrees
of yaw on now as the car's sliding sideways.
And it's about 15, 20 meters offline.
Soon as it starts responding and coming back, I've got to
get the power back down again.
Because I've only got another mile and a half to the
measured mile.
Got to get up about 750 miles an hour.
So it's full power.
Start to wind the lock back off.
So that will the car straightened up on the line
going into the measured mile at supersonic speeds.
And of course, I've got to do that two ways within one hour
to set the world record.
CHRIS HARRIS: This was my qualifying lap.
I'm a bit of a pussy through paddock, I have to admit, but
it left us 13th on the grid.
Andy qualified for the first race.
I did the second.
Neither of us made much of an impression on
the computer screens.
His excuse was valid.
He hadn't raced a car at Brands before, and this was
only his second event.
Mine was more tenuous.
I felt that if I bent the car again, I was
probably a dead man.
And the combination of seat and
downforce was plain torture.
That's [INAUDIBLE]
of what you're trying to achieve.
Because we're both learning that the [INAUDIBLE]
car, but it has lots of aero effects here in two places,
Paddock Hill and [INAUDIBLE].
For me, an aero effect on my car is when the car forces you
to do something your brain tells you you shouldn't, to
turn at a speed that mechanically you think is not
suitable for the vehicle, that means the
wings aren't working.
Is that a reasonable description of it?
ANDY GREEN: Absolutely right.
And the classic here is coming into, at the bottom of Brands
Hatch, the S-bend, Surtees, for those that
have driven it here.
And first day I was braking quite hard.
By the time I got to the end of the first day, you can go
through there almost flat.
So I'm braking a little bit.
Now I'm just lifting very slightly, and the car is going
through like everybody promised it would be.
But it doesn't make sense.
The performance of the Radical loaded up at best part of 100
miles an hour, it just does stick to the tarmac
astonishingly.
CHRIS HARRIS: We had a discussion the other day about
the aero when you go to 1,000 miles an hour.
That's remarkable.
So talk us through the speed ranges of the car.
ANDY GREEN: First of all, the aerodynamic forces are
absolutely dominant at the high speeds.
To go about 15 years to Thrust SSC, one degree nose down
would generate 10 tons of download on the front and
crush the front suspension into the desert.
One degree nose up would generate 10 tons of lift.
The car would pitch up, pull 40 G. The body work comes off.
Engines tear out the bottom of the car.
That's the end of my interest in the afternoon.
So that precision, it needs to be incredibly precise.
And with the thrust shape 15 years ago, we didn't have the
tools to set that so it was the same
angle all the way through.
We actually had to change the pitch angle of the car as it
was accelerating.
The problem with that is if that system fails, you finish
up in an uncomfortable place.
And we limited with Thrust SSC, because we were only just
going supersonic.
Step forward 15 years.
We're now trying to do 1,000 miles an hour.
That's almost 40% above the speed of sound, like 1.4.
So tweaking the car a bit isn't the solution.
We're actually going to have to solve the fundamental
problem of a shape which generates virtually no lift or
downforce all the way through the speed range.
And that's been the single most difficult technical
problem we've had.
We've had Swansea University, who are the world's leading
experts in this, they developed the technique 15
years ago that we used.
Intel have given us a huge amount of computing power.
And we've done some genuinely world leading modeling
supersonic ground effect, and got a shape which, at all
speeds, will stay on the ground.
And that actually, when you think about it, is the only
safety requirement for a land speed record car.
As long as you can keep it shiny side up, keep all the
wheels on the ground, and the fin is the right size to keep
it pointy end forwards, you've cracked it.
CHRIS HARRIS: But you don't want to drive it into the
ground so hard that it disrupts the surface and makes
it unsafe [INAUDIBLE].
ANDY GREEN: Exactly.
That's why the aerodynamics have to be so precise, to
actually bound the load so you don't crush the wheels, but
you don't at any stage finish up with them lifting.
Or, with the front-rear distribution so far out,
particularly front-heavy, the car becomes
uncontrollable as a vehicle.
Because before it becomes totally dominated by the
aerodynamics, which is 500, 600 miles an hour high speed,
but at 300 or 400 miles an hour, which is slow to medium
for this car, it is behaving like a car at least as much as
its behaving like an airplane.
So it's dominated by its vehicle dynamics as well.
And we need to get that balance right.
CHRIS HARRIS: 300 to 400, slow to medium speed.
It's a different reality, isn't it?
Anyhow, back to the racing.
Andy started race one, and in the dust and mayhem held his
nerve for 24 minutes before handing over to me.
For his first time in a fast racing car, it really was a
stellar effort.
The change was reasonably smooth, but there was a
problem with my reproductive equipment.
My right spud was being crushed by the belt.
This was agony, so I tried frantically to adjust on the
small straights.
It didn't work.
I then got overtaken a few times.
The only thing for it was a pit stop for testicular
adjustment.
As racing driver excuses go, you have to
admit it's pretty good.
We started 16th.
We finished 15th.
Anyways, this is Andy talking about rear suspension design.
ANDY GREEN: We have to have the rear wheels outside the
body work, first of all because the shock waves under
the body will tear up the desert.
This is a dry lake that we're going across.
The front wheels and the shock waves between them will rip up
the surface they're running over.
So we need some fresh surface outside the body work for the
rear wheels to run on.
And we need them wide enough apart that we've got some
really good rollover stability so that even if the car does
get a little bit sideways, there's no chance of it
digging in and rolling over.
So we've got a 50% safety mark on the rollover ability.
Pushing the wheels out puts the strut out into the airflow
and the shock waves over them, the sudden deceleration of the
air, supersonic as it hits those struts.
Sudden slow-down, the pressure goes up.
It's like traffic suddenly stopped and all the cars
compressed.
Finish up with a high-pressure ridge around
the back of the car.
It's underneath the car, lifts the tail off the ground.
Now, the way to fix that, simple way, is to angle the
struts down.
Problem is when you're subsonic, say 600 miles an
hour, no shock waves, so no high pressure.
But the angled-down struts are now generating 10
tons of down load.
So you've got to find a solution that works subsonic
and supersonic.
And although it's more a combination of things, a
significant part is the double wishbone.
So you've got a pair of structure at the top, pair of
structure at the bottom supporting the wheels.
That pair at the bottom will be filled in, so it's almost
like a big delta plane, like a Vulcan wing.
CHRIS HARRIS: Race two was a little more straightforward
because I didn't have any knacker problems.
This time I started and Andy took over.
We started in 13th.
We finished in 13th, and everyone
was very happy indeed.
I hope you'll join me in wishing everyone involved with
Bloodhound the very best of luck.
And I want to leave it here with Andy talking about the
numbers involved in Bloodhound, because that's
what it is, really.
It's a collection of amazing numbers.
And that's what always captivates us about the land
speed record.
ANDY GREEN: Our car's going to have three engines.
It's got a state-of-the-art Typhoon jet engine, nine tons
of thrust, which is about 65,000 horsepower.
We've got a hybrid rocket, Falcon rocket which gives us
about 70,000 horsepower.
And to pump the hybrid rocket, we've got a Cosworth Formula
One engine, because we need 700 horsepower just for the
rocket pump.
[CAR ENGINE]
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【賽車介紹】訪問 SR3 記錄保持人-Andy Green  Racing a Radical SR3 with Andy Green, Holder of the Land Speed Record -- DRIVEN

9500 分類 收藏
Furong Lai 發佈於 2012 年 12 月 15 日
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