Theoretically questions aero Vs weight

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marmer
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Theoretically questions aero Vs weight

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Does aero do more than just increase weight so there is more weight pushing tyres into the ground. If so couldn't teams run a really heavy car with a very slippery car. Be able to achieve the same cornering speeds and higher top speed just with less acceleration

Or am I missing something

I guess weight could cause extra lateral load during cornering but why doesn't aero also do this to the tyres weight is weight is it not

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Big Tea
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Re: Theoretically questions aero Vs weight

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marmer wrote:
17 Dec 2018, 13:19
Does aero do more than just increase weight so there is more weight pushing tyres into the ground. If so couldn't teams run a really heavy car with a very slippery car. Be able to achieve the same cornering speeds and higher top speed just with less acceleration

Or am I missing something

I guess weight could cause extra lateral load during cornering but why doesn't aero also do this to the tyres weight is weight is it not
They have to accelerate and retard the extra weight, and stop it flying sidewards in the corner.
I believe a more technical explanation will follow (from someone who knows what they are talking about :D )
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Tommy Cookers
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Re: Theoretically questions aero Vs weight

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marmer wrote:
17 Dec 2018, 13:19
I guess weight could cause extra lateral load during cornering but why doesn't aero also do this to the tyres weight is weight is it not
the weight is a force (gravity acting downwards so through the tyres to the road) proportional to the mass of the car
to take a corner the car will need a lateral force proportional to the mass of the car
the lateral force available from the tyres in cornering is proportional to the downwards force on the tyres
whether that downwards force is weight only or weight force plus some aero downforce

for a given corner without aero DF....
the downwards force from the tyres depends on the car mass
the lateral force needed also depends on the car mass

for the same corner with aero DF .....
the downwards force from the tyres is greater
but the lateral force needed is not greater
so (if we want) corner speed can be increased

Just_a_fan
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Re: Theoretically questions aero Vs weight

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marmer wrote:
17 Dec 2018, 13:19
Does aero do more than just increase weight so there is more weight pushing tyres into the ground.
Downforce doesn't increase weight. That's where you're going wrong.
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marmer
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Re: Theoretically questions aero Vs weight

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Just_a_fan wrote:
17 Dec 2018, 16:02
marmer wrote:
17 Dec 2018, 13:19
Does aero do more than just increase weight so there is more weight pushing tyres into the ground.
Downforce doesn't increase weight. That's where you're going wrong.
so what force is affecting the tyres then

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jjn9128
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Re: Theoretically questions aero Vs weight

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marmer wrote:
17 Dec 2018, 17:15
Just_a_fan wrote:
17 Dec 2018, 16:02
marmer wrote:
17 Dec 2018, 13:19
Does aero do more than just increase weight so there is more weight pushing tyres into the ground.
Downforce doesn't increase weight. That's where you're going wrong.
so what force is affecting the tyres then
He's right aerodynamic downforce isn't weight - Weight being the force produced by mass under the gravitational constant and downforce being the effect of air pressure on the surfaces. The reaction at the wheels normal to the ground is equal to the sum of both:




Technically you can split those into 2 as the % mass and % downforce at each axle will be different, ~45% mass on the front and ~40% downforce for an F1 car (depending on the track). You could even split them into 4 for each wheel equations to account for the weight transfer and downforce shift in pitch/roll/yaw.
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Just_a_fan
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Re: Theoretically questions aero Vs weight

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marmer wrote:
17 Dec 2018, 17:15
Just_a_fan wrote:
17 Dec 2018, 16:02
marmer wrote:
17 Dec 2018, 13:19
Does aero do more than just increase weight so there is more weight pushing tyres into the ground.
Downforce doesn't increase weight. That's where you're going wrong.
so what force is affecting the tyres then
The "lift" from the wings and the floor. This is the same lift as a plane makes but facing downwards. This "lifting force" pushes the car's body down towards the track. The suspension transfers that downward force in to the tyres. Ideally, you'd have the force applied directly to the wheel uprights but that is illegal in F1.
If you are more fortunate than others, build a larger table not a taller fence.

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hollus
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Re: Theoretically questions aero Vs weight

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marmer wrote:
17 Dec 2018, 17:15
Just_a_fan wrote:
17 Dec 2018, 16:02
marmer wrote:
17 Dec 2018, 13:19
Does aero do more than just increase weight so there is more weight pushing tyres into the ground.
Downforce doesn't increase weight. That's where you're going wrong.
so what force is affecting the tyres then
Let's try less technical.

The force acting down on the tires is the total of weight plus downforce. Weight from mass and gravity, downforce from aero.

Bus as said in a post above, weight comes together with mass and mass resists acceleration. The more mass, the more resistance to: accelerate the car, brake the car, turn the car.
So increasing mass gives you extra "push" on the tires, but also creates slower acceleration, longer braking distances and slower cornering. The positives and negatives kind of cancel each other out, actually.

Downforce adds no mass, so it adds no resistance to accelerating, braking and turning. Resulting in better acceleration, better braking and better turning.
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Just_a_fan
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Re: Theoretically questions aero Vs weight

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But downforce does add drag which does resist acceleration as speed increases (but then also helps braking so probably cancels out to a good degree).
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godlameroso
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Re: Theoretically questions aero Vs weight

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Tommy Cookers wrote:
17 Dec 2018, 13:59
marmer wrote:
17 Dec 2018, 13:19
I guess weight could cause extra lateral load during cornering but why doesn't aero also do this to the tyres weight is weight is it not
the weight is a force (gravity acting downwards so through the tyres to the road) proportional to the mass of the car
to take a corner the car will need a lateral force proportional to the mass of the car
the lateral force available from the tyres in cornering is proportional to the downwards force on the tyres
whether that downwards force is weight only or weight force plus some aero downforce

for a given corner without aero DF....
the downwards force from the tyres depends on the car mass
the lateral force needed also depends on the car mass

for the same corner with aero DF .....
the downwards force from the tyres is greater
but the lateral force needed is not greater
so (if we want) corner speed can be increased
Beautifully stated! Downforce adds a downward force, but does not increase the inertia of the car, just drag.
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Vyssion
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Re: Theoretically questions aero Vs weight

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marmer wrote:
17 Dec 2018, 13:19
Does aero do more than just increase weight so there is more weight pushing tyres into the ground. If so couldn't teams run a really heavy car with a very slippery car. Be able to achieve the same cornering speeds and higher top speed just with less acceleration

Or am I missing something

I guess weight could cause extra lateral load during cornering but why doesn't aero also do this to the tyres weight is weight is it not

I made a post on this a while ago which I will quote here for you - hope it helps.


Vyssion wrote:Essentially, the generation of downforce is the way that allows for the car to (in lamans terms) "be heavier than it actually is, without the bad stuff that comes with an increased weight".

The downforce and the normal (weight) force of the vehicle is the simplified mechanism by which the tyres gain their grip. And again, over-simplifying things for a purely aero discussion, the more grip you have, the faster you can theoretically corner at. \mu is the coefficient of friction here.


The "N" denotes normal force which is made up of the vehicles weight force and any downforce currently being produced.


If you combine this equation with the formula for centripetal acceleration (which could be adapted to fit a corner if a constant radius)

and rearranged to give:


Then you get the following formula:


This then shows that for a constant coefficient of friction, that velocity is proportional to (meaning that an increase in the right hand side of the equation will increase the left hand side). If this is differentiated to get this in terms of time, it shows that time is proportional to (or simply that it is inversly proportional).

The important term here is this which is often referred to as the "specific downforce" of the vehicle. So if we are to increase this term, by means of increasing downforce or reducing the cars mass, the theoretical maximum velocity we can corner at will increase and hence the time taken to travel the corner will decrease. Add in that since you can carry more speed through the corner, braking time is reduced in the lead up to it and the acceleration beyond it begins from a higher speed, and you can begin to see the benefits.

By increasing mass initially, this would have the effect of decreasing this term, which would be counter productive.

This argument here is purely from an aerodynamic standpoint (and extremely simplified!!!) though and doesn't even mention things like the weight transfer or suspension changes and other vehicle dynamic effects that would be required to handle the higher initial weight during a race. But hopefully it helps explain why it is the way it is!!
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