Today we are going to talk about the braking systems on a Formula One
car, how the various parts work individually and how they work
together as a combined system.
So, when a driver presses on the brake pedal in a
Formula One car, the force he is applying to the brake pedal
is applied to two master cylinders. One cylinder is a fluid that is linked
to the front brake system and the other cylinder is linked to the back
brake system. And that pressure in that cylinder goes through a brake
line and onto the calliper, onto the brake disc itself. And that
pushes the pads onto the disc and that’s what slows the car
down. On the back of the car, the system is a bit more
complicated than that because we now have
Energy Recovery Systems and we need to deal with
those to get the brake balance right. In your road car at home,
when you press the brake pedal, you have an assist system, a servo-assist.
So that multiplies the pressure you are applying into the master cylinder,
to give you the braking effort. On a Formula One car, we can’t do that.
What happens is the driver has to provide all that force. So, it’s a huge
amount of effort the driver is making. And in fact, if they were to just sit in the
car normally and apply the brake pressure, they couldn’t press the pedal hard enough.
In order to do that, what happens is they are actually using the deceleration of the
car and their own bodyweight sliding in the car
to actually get the amount of pressure that they need. So, the driver is not only
having to press the brake pedal really hard, he’s also having to withstand
the huge G-Forces. So, that can be a G level of sort of five, so that’s five
times the pressure you get of gravity. So, if you imagine his head and his helmet
is sort of between five and 10 kilos, for that peak part of braking the driver is
getting as much as 50 kilos into his neck.
So, if we look at a brake disc, this is a brake disc off of a Formula One
car. When we are braking at maximum brake
temperature, so on a high-duty circuit, the temperatures could be up to 1,000 °C
on one of these carbon discs. As the car goes down the straight, the air
is coming through the brake duct, coming out through the upright and that is cooling
the disc itself. So, by the end of the straight, temperatures could be as low as 200°C
and those temperatures are really important. The disc itself has up to 1,000 holes
and they are there just to try and get the maximum surface area and
the maximum cooling we can achieve. In actual fact, because we have
removed so much material from the brake disc, the peak temperatures
are actually higher because the thermal mass of the disc is lower
than it would’ve been years ago. But, it’s not that individual peak that’s
important. It’s the repeated braking that occurs. Repeated braking is where
we don’t get the disc cool enough by the end of the straight and the temperatures
come back up. That is when we see these really high temperatures. So, what we
are trying to do is get as much cooling as we possibly can. It’s important to
understand why handling the brake temperatures is hard. If the disc
gets too hot, so when we talked about that 1,000°C at the end of the
straight, what happens is we start seeing fade. It’s a bit like a car going
down a hill, when you get to the bottom of the hill sometimes the brakes are less
effective and that’s because the discs are too hot. Equally if the discs are too cold,
something we might see at end of straight, then we don’t get the bite,
we don’t get that initial braking that we are looking for, so we have to
manage the temperatures of the discs really well. And we do that with the
flow that’s coming through the brake ducts here. And that flow is fed through
the duct and through the upright and onto the disc. It’s also there to cool the
calliper and also the pads that are inside the calliper. All of that has to
be kept at the right temperatures to get the peak braking performance.
It’s also really important how we deal with the flow that comes out of the disc.
That hot air that’s trapped with inside the drum, how that feeds over the
wheelrim and also around the tyre is really important for the
tyre performance because we need to keep those in the right operating window too.
You may have heard on the TV the drivers talk about brake balance
and also brake migration. So, what’s happening there is it’s important to
get the amount of braking effort at the front and the braking effort
at the rear in the right balance. Because what you are trying to do is
maximise the rate at which you decelerate, so, it’s really important that you are
extracting the most grip from the front tyres and from the rear tyres.
And we do that by changing the balance and that’s an adjustment the drivers
can make inside the car. When we talk about brake migration, what we are
actually talking about is balance migration. So, as the driver presses on the brake pedal,
we also alter the balance front to rear using the Energy Recovery Systems to get an
optimal braking performance.
On a typical road car, you might be able to brake at say
around 1G. On a Formula One car, at peak braking we are braking at
nearly 5G. And the reason we can do that is one, the tyres themselves
have more grip. We have more powerful, more capable brakes but we also have
the aerodynamic performance of the car. At the end of the straight, the aerodynamic
load might be three, maybe even four times the total weight of the car and that load
is pushing into the tyres and that allows us
to generate much more grip at the tyres and therefore more braking performance.
So, one of the questions we quite often get asked is, why is it so difficult
to brake into the first corner? Well, as we talked about earlier,
it’s really important to have the right temperature in the brakes.
So, if the brakes are sitting there cold because we have been sitting
on the grid waiting for the start, the drivers don’t really know quite
how much grip they are going to get from the brake system,
quite how hard they should press the brake pedal, to get the right braking
force. If they don’t press hard enough,
then they could lose their advantage into the first corner. And if they press
too hard, then they could lock up the brakes and go straight on.
So, it’s difficult to get that balance right for the driver.
So, two of the most difficult tracks for the brakes are Monaco and Baku
but for different reasons. In Monaco, the problem is that the
car speed is generally low, so we don’t get the huge amount of air rushing
through the brake duct we might get at faster circuits. But what we’ve
got are these repeated corners. So, each corner the brake temperature
rises as we press the brakes, we don’t get enough cooling down the next straight,
then we get another application of the brakes and the temperatures keep going up and up.
So, that’s one that’s really challenging for
the brakes in terms of the maximum temperatures. In somewhere like Baku,
Baku is a funny circuit. It’s got half like Monaco and half more like Monza,
so a high-speed circuit. So, what happens there is we’re having to give enough brake
cooling for those twisty parts of the circuits where the average car speed is low but
then we have also got these huge, long straights. Which means that the
brake temperatures get really low at the end of straight, so going into
those corners after the very long straights, the brakes are cold and
therefore they lack the bite that the drivers would want.
In these different circuits,
we have to manage the brakes and that’s the drivers and the engineers
working together. The engineers determining what the right set-up is
and the drivers knowing how they need to manage the brakes within the race.