Racing is a tricky business and between mistakes
and failures a driver can never guarantee that their car will stay on the track.
With spectators, marshals, TV and track staff needed nearby, impenetrable perimeters around
the track are needed to stop any out-of-control cars.
With such high speeds involved in racing, motor sport has had to come up with all manner
of solutions to stop an uncontrolled car without injuring the driver. In this video we’re
going to look at the brief history of barrier technology in F1 and how thoughtful engineering
has helped solved the problem of cars flying off-circuit, as well as introducing some problems
of its own. Douglas Adams once wrote, ‘it’s not the
fall that kills you; it’s the sudden stop at the end.’ And so it is with racing accidents.
The risk of serious injury in a crash is mostly from massive acceleration Acceleration is the rate of change in velocity.
Acceleration produces a force acting on you. You can very gradually drive a car from zero
to two hundred kph and not really feel anything, but an F1 car can do it in a few seconds and
it’ll feel like you’ve been kicked in the chest. It can come to a stop even quicker.
Acceleration and deceleration are essentially the same thing, by the way. 0 to 200 kph in
3 seconds has the same acceleration as 200 to 0 in 3 seconds… just in the other direction.
The two components of acceleration are: the change in speed, and the time taken to change
speed. If an F1 car drives straight into a rigid
concrete wall at 100 kph, it’s going to go from 100 to 0 in milliseconds. That’s
huge deceleration, and the larger the deceleration the larger the force you’ll experience as
a driver and the more dangerous it will be. This is massive energy transfer to your body,
your organs and your brain. F1 accidents will often be reported in “g”
– e.g. a 21 g accident. G is a unit of acceleration and if you know that slamming on the brakes
in a normal road car at 60 mph will produce less than 1 g of deceleration you can start
to imagine just how massive a 30 g impact can be.
A big part of the design of F1 barriers in F1 is to reduce the deceleration by lengthening
the time and distance is takes to stop an F1 car upon impact.
I’ll talk about this ability to reduce deceleration as ‘absorption of momentum’ or ‘energy
absorption’, with the barrier ideally taking away some of the energy of the impact from
the car and driver. And the kinetic energy of a moving object
squares with speed, so an F1 car going 150 kph has 2.2 times the energy of a car going
100 kph. At 200 kph the energy is 4 times greater. You can see how the duties of a crash
barrier start to stack up! Back in the way back when, straw bales were
often used as trackside barriers. Circuits were frequently constructed in towns,
airfields and public roads and drivers would be exposed to trees, telephone poles and walls
– hefty objects they really didn’t want to hit.
Straw bales, then, were cheap and accessibly items that, having some weight to them, could
absorb some of the momentum of a moving car when struck. If you collide with a stationary object and
make it move, this is a transference of momentum from one object to another. Think snooker
balls. Straw bales are a light touch solution that
allow cars to slow down more gently than driving into a tree.
They do, however, come with a huge list of negatives.
They could snag the car and flip is over, which is especially dangerous when your car
looked like this. In snagging a car they could also send it
into a tight spin, which is a large transfer of rotational energy that can lead to injuries
like whiplash. Once struck, straw bales leave straw all over
the track, which is slippery and dangerous. And, worst of all – it turns out that straw
is extremely flammable. The most famous bale-related horror was when Lorenzo Bandini crashed and
flipped at the Monaco Grand Prix in 1967, ending up trapped and on fire in a pile of
straw bales. He ultimately succumbed to his burn injuries.
Bales were banned in 1970. Catch-fencing was a pretty popular form of
barrier for a while as a relatively cheap and cheerful way of keeping cars from flying
off circuit. This is a simply a wire fence design, cabled
together to form a long chain of fencing at the edge of the track.
Cars could fly into it and the fence would deform and ‘catch’ them, absorbing the
impact by putting the car’s energy into deforming the shape of the fence.
Unfortunately, this too was fraught with problems: The fence actually deformed so readily that
it can wrap around the car and it make it difficult to extract the driver. In cases
of fire or injury you can quickly see the problem here.
The fencing could also wrap around the drivers themselves – Carlos Reuteman was nearly
choked by one at the 1981 South African GP. And – as the fencing deformed so easily,
the posts that held the catch fencing up could be whipped around with speed and could strike
and injure the drivers. At that same South African GP, Geoff Lees was knocked out by
a catch fence post. They are also no easily rebuilt once they’ve
been hit, which is a problem if you want to keep a race going without delay.
This type of catch fencing was also banned and if you hear the term catch-fence in F1
today it’s normally in reference to reinforced debris fences which are never the main component
of stopping cars. One thing that’s important to consider in
barrier choice and placement is the angle of impact.
Around a corner, a car is likely to fly off the road and hit a barrier at a steep angle
[angle is trajectory, not car-pointing angle] On a straight, a car is more likely to hit
the barrier at a shallow angle. What we’re actually interested in in both
cases is how much speed the car is carrying perpendicular to the barrier. Whatever its
trajectory, we can think of a car’s energy being carried in two component directions:
parallel to the barrier and perpendicular to the barrier.
In a steep angled crash, most of the speed will be carried perpendicular to the barrier
and we’ve got to consider how to absorb that energy into the barrier.
But in a shallow angle, most of the energy is carried parallel to the barrier with only
a small component straight into the barrier. In these cases we need to absorb the energy
in this parallel direction by minimising the deformation of the barrier and slowing the
car down with friction by forcing it to slide along the wall instead.
Concrete walls have done a great job at this. They are terrible at absorbing energy in the
perpendicular direction as they are extremely rigid and immobile. You really don’t want
to hit them head on. But they are great at deflecting cars and absorbing momentum by
friction. Along straights we can increase the chances
of a shallow crash angle by bringing the walls closer to the track edge. When the car loses
control it take time to travel through a curve that will transfer its trajectory from parallel
to perpendicular – bringing the wall closer forces it to hit the wall at a shallow angle.
This works great if you’ve got less space on your circuit or want to bring a grandstand
up close. The long back straight in Canada is a great example of this.
A more common sight in F1 to the concrete wall is the humble guard rail.
The guard rail has a distinct wobbly W-shape to it and there’s a good reason for that: See, if you bend a plane of material in one
direction it’s really hard to bend it in the other direction. Try it with a piece of
paper – once you’ve bent it over, it really doesn’t like being bent the other way. That’s
also the reason we hold a pizza slice with a bend, by the way, because it won’t sag
if it’s already curled along it’s length. So a guard rail is very strong along its length
and if a car hits it at a reasonably shallow angle it will deform only slightly, absorb
the energy of the impact and redirect the car along its length, bringing it to a stop
without throwing it back out onto the track (in most situations).
The post and spacers behind the rail are designed to bend and deform to absorb some of the impact.
Of course, severely damaged guard rails are hard to repair, can be expensive to replace
and only really work in lower speed areas with limited run off space, like in Monaco.
They’re ideal for Monaco. But for maximum versatility, let’s meet
a well-loved and famous friend, the Tyre Wall. This is simple to describe – it’s a bunch
of tyres stacked and lined up to make a soft wall for the cars to safety crash into .
We’ve got advantages right off the bat: used tyres are cheap and readily accessible.
Tyres are soft and squishy, which is great for energy absorption – energy from the
speeding car goes right into deforming the rubber like a spring.
Over the years we’ve improved the efficacy of tyre barriers in a number of ways.
The tyres are strapped or bolted together, not stacked loosely.
Loose tyres will be scatter upon impact leaving only tyres directly in the impact zone to
absorb the energy. Strapping tyres together allows the barrier to act as one elastic unit.
Upon impact, the tyre wall in its entirety spreads the energy absorption out through
its structure. The more tightly you attach the tyres to each
other, the stiffer the wall, just like a more tightly strung trampoline.
Similarly you can adjust the stiffness of a tyre wall by the number of rows of tyres.
You tend to use between two and six rows in one tyre wall, with more rows creating a stiffer,
less flexible wall. A stiffer structure is better in zones where a high speed impact
is likely as they can absorb much more energy, where a shallow, soft wall might allow the
car to hit the back wall. Tyre walls are now wrapped in large belts
or coverings. This is useful in a number of ways:
1- with exposed tyres a glancing blow can snag the car into an jarring spin. A smooth
surface will allow the car to glance off the barrier in a shallow collision
2- it is much harder to penetrate a tyre barrier that’s covered. With exposed tyres, a car
can embed itself like a dart, making extraction difficult and increasing the chances of being
hit in the head – though this is less likely now we have the Halo.
Another innovation that often goes unseen is that tyre barriers in F1 tend to have inserts
– these are plastic tubes that sit inside the tyres themselves, making them harder to
squish – i.e. it takes more energy to deform the tyres. This can double the energy absorption
ability of a tyre wall. Finally let’s quickly look at Tecpro barriers
These are specifically designed, tessellating crash barriers that come in two flavours:
A red ‘absorbent block’, a hollow foam block that squishes fairly easily
And a grey ‘reinforced block’ with strong foam skin, a squishy foam core and a thing
steel wall inside to present cars from penetrating through the barrier,
They are actually quite similar to belted tyre wall in what they are trying to achieve
but are designed to be quite adaptable in how they can be arranged as well as their
tessellating shape allowing them to fit around different corner shapes.
They have had a few minor problems over the years. One is that, with the low noses on
F1 car, they can be lifted upon impact and end up burying the cars instead of slowing
them down correctly. [PICTURE OF SAINZ]. Maldonado actually managed to rip a TecPro
barrier free in Monaco and drag it onto the track so perhaps their weight is not quite
correct for all situations. The matter of bringing fast moving out-of-control
cars to a half safely and in a controlled manner is a very tricky business and a lot
of engineering and study has gone into finding solutions that are adaptable, affordable,
reuseable after impact and rebuildable (to avoid long session delays).
In F1 in particular, it seems that our best friend will continue to be the humble, adaptable,
predictable tyre barrier and it’s easy to see why.