For 2019 the rules around the minimum allowed weight are changing slightly.
This year, the total weight of the car and driver together would have to weigh at least
733 kg excluding fuel Next year, the driver and their seat must
meet a minimum weight on their own.
It’s expected this will be 80 kg.
The rest of the car, excluding fuel will have to make up the remaining 653 kg.
A minimum weight is enforced for reasons of safety – to ensure the teams don’t skimp
on their cars strength in pursuit of speed.
Every kg of mass you have requires more energy to accelerated around a track, as you’d
know if you ever had to run while carrying massive bags.
By the way, mass and weight do mean different things but I’ll be using them fairly interchangeably
throughout this video as it doesn’t really matter in this context.
If you want to know the specific differences I’ll explain over the credits.
OK, so now we have to weigh the driver and seat separately to the rest of the car.
In what way is this different to weighing the car and driver as one mass?
A smaller 65 kg driver and a larger 75 kg driver will weight identically when combined
with their cars, so why is it so much easier to have a smaller driver in your car that
drivers have been known to lose unhealthy amounts of weight to benefit performance?
The answer is weight distribution.
See cars are built as underweight as possible and then brought up to the minimum weight
via ballast.
Ballast is the term given to heavy material strategically placed around the car for stability.
Ships and aeroplanes also use ballast.
Often heavy metals like tungsten are used to this purpose.
As they are so dense, very heavy masses can be placed precisely without taking up room.
So how does weight distribution affect an F1 car?
Well, there are a number of factors at play here.
One is how much you want to load up the tyres.
See the tyres are the only points of the car that touch the ground so ultimately all the
weight of the car is borne by the tyres.
If you force a tyre to bear too much weight it can start to overheat more quickly as it’s
used, which can lead to degradation and loss of grip.
If a tyre has too little weight pushing it into the ground then it is more prone to slip
and can more easily lock under braking.
Pirelli of course design front and rear tyres with certain expected weight demand thresholds
and in fact the rules mandate that during qualifying (when the car is low fuelled) the
“weight applied on the front and rear wheels must not be less than 333kg and 393kg respectively
during qualifying.”).
Secondly, we have to consider acceleration All the acceleration comes from the rear wheels,
as these are the driving wheels.
More weight over the rear axle (to a point) leads to better traction through and out of
corners, meaning better acceleration.
Under balance the rear of the car and traction will suffer.
What else happens when we move ballast around between the front and rear of the car?
Well now we need to have a little understanding of two things: moments and inertia.
A moment is a turning force.
Specifically, when we think about moments, we think of a pivot point and applying a force
a certain distance from that point.
Imagine a door.
It shouldn’t be hard, there’s probably one right behind you.
If you apply a force – i.e. push – against the door close to the hinge it’s much harder
to get the door to turn than if you apply the same force far from the hinge.
Just FYI: the actual definition of a moment is the force you apply multiplied by the distance
from the pivot that you apply it.
So on a see saw, you can place a 1 kg weight 2 metres from the pivot and a 2 kg weight
1 m from the pivot and it would all balance out.
So, with that in mind, think what would happen if we put a 100 kg weight right at the end
of the see-saw, let’s say it’s 3 metres out.
It would be really hard to get the see-saw moving, right?
But if we moved the mass more towards the centre, suddenly it becomes a whole lot easier,
doesn’t it?
And that’s the first lesson – it’s hard to turn something whose weight is far from
the pivot point.
You can try this – carefully.
Hold a hammer from the end of the stick part and start to swing it – carefully.
It’s much harder work that holding it from the hammer end, because this time all the
weight is much closer to the turning point.
So back to the F1 car: because of its layout, you’re turning it around a point between
all the wheels.
You don’t want the centre of mass to be too far from the centre of the car or it will
require more energy to get the car turning quickly and it won’t be particularly nimble.
Now let’s consider inertia But quickly first, let’s define the ‘centre
of mass’, which you’ll often hear as the ‘centre of weight’ though that’s less
accurate.
It’s very simple – the centre of mass is the average point of all the mass in an
object.
A pretty regular, homogenous cuboid of plastic would have a centre of mass bang in the middle.
But if that block was half plastic, half lead, then the centre of mass would be way more
towards the lead end of the block as the lead part has more mass.
Therefore, on average, the mass of the block would be much more towards the lead end, and
that’s what the centre of mass represents.
It’s also the balance point of the object.
If you placed that plastic/lead block on its centre of mass, if would balance perfectly.
With our F1 car, if we start moving the centre of mass around by re-positioning our ballast,
we’ll see the weight load on each tyre change accordingly.
Inertia then.
Inertia is the resistance of an object to change in velocity.
If a car is travelling along, it actually doesn’t want to be moved around.
It’s going to keep going as it is until you put some force in to make it do something
else, like braking or steering or accelerating or crashing into a barrier.
The more mass something has, the more resistant it is to change.
A double decker bus driving at 60 miles an hour is harder to stop than a Mini Cooper
at the same speed.
So, bearing inertia in mind – that bodies of mass will tend to keep on going and resist
being yanked about – let’s take a look at a car cornering with all its weight at
the rear.
The car is going straight and then turns right.
But all the weight wants to keep going straight.
As the front steers in, the back really wants to keep going and this leads to the back sliding
out, which we’d call oversteer.
On the flip side, if we bunged all the weight at the front, all the weight at the front
would want to carry on.
The front is resistant to being turned in and struggles to get the car steering as much
as we like.
This is called understeer.
Finally, we’ve looked at front-to-read distribution but let’s thinking about top-to-bottom weight
distribution See, ballast tends to be placed as low as
possible to lower the overall centre of mass.
But why is this useful.
Well let’s consider inertia again – particularly if the centre of mass is quite high up.
The car will turn in, but all this mass will resist.
So the top of the car will be the most sluggish to respond and lean out as the bottom of the
car moves out from under it.
This is car roll, when the car rotates along the centre line.
The problem with a car rolling too much is it starts to unbalance the tyre loads.
The inside tyres start to lift and the outside tyres take all the weight.
Body roll is heavily controlled by suspension engineering – but that’s definitely for
another video.
Bringing the overall weight as low to the ground as possible is a great help at reducing
body roll and keeping the car balanced through the corners.
Which brings us back to the driver.
See a taller, heavier driver will naturally be carrying their weight quite high up compared
to a lighter driver with the extra low, low ballast.
Enforcing the driver/seat weight to meet a strict minimum means a lighter driver loses
a lot of the advantage of having a lot more ballast to be strategic with.
The obvious, fairest place to put the mandated seat ballast (to bring the weight to 80 kg)
is not down on the floor but halfway up the seat, roughly where the actual driver’s
centre of mass is.
I’d hope the FIA mandate and minimum height for seat ballast.
I hope this helps you understand why the new rules are finally separating the minimum weights
of the driver and car.
Any questions – leave them in the comments.
Thank you to my patreon patrons for supporting me with these videos.
And now – what’s the difference between weight and mass?
Well mass is the amount of “stuff” in an object.
I.e.
a human adult is made of, say, 70 kg of stuff.
Weight is the measure of how much that stuff pushes down towards the ground.
Now, for a the most part in every day life, these things are pretty similar.
A 70 kg person pushes down with the weight that 70 kg of anything would, right?
Except if they’re going up in a lift in which case they push down harder.
Down in a lift?
They push down less.
On the moon?
They weigh less.
In space, they weigh basically nothing.
But their mass stays the same.
See, once you start doing things with a mass, the weight can change quite a lot, which is
why they are technically different things but you don’t have to think about that when
following a recipe.
Unless you’re a chef on the moon.