Aerodynamic balance biased towards inside or outside tire?

[Tim.Wright]

Hi all,

Just wondering if during any given cornering situation, would you want the aerodynamic balance to be closer towards the inside pair of wheels or outside?

Intuitively I would think you would want to give more downforce to the inside tires; as those are the unloaded tires during a corner is this correct?

I am thinking about say, splitting the drs flap in half, and then having each 'flap' open or close by varying amounts to shift the aero balance left and right (ignoring the foward and back shift this would also cause, would need a similar mechanism on the front wing or something). Would this have any unwanted downsides if shifting balance towards inside side of car?

Thanks!

Greatly simplified but:

In terms of grip...
The inside tyres have a higher grip sensitivity to downforce (due to tyre load sensitivity), so adding X kgf of downforce to the inner wheels will give you more grip than adding X kgf of downforce to the outer wheels. But you will always end up with more grip by simply adding X kgf of downforce to both sides simultaneously if you can.

Or in other words - if you divide the DRS into 2 halves - there is no grip advantage in only using one half of it.

In terms of balance...
An asymmetric aero element will create a yaw moment which will change your oversteer/understeer balance. Whether that's a good thing or not depends on the baseline balance.

[sosic2121]

Yeah. And It's been done.

Pagani Huayra raises it's flaps on the inside to increase downforce on the unloaded tires and prevent roll.

Zenvo has a solution where they flip the whole back wing to achive the same thing.

https://thumbor.forbes.com/thumbor/960x ... it%3Dscale

That wing will cause a small reduction in downforce but it will give an increased lateral force albeit likely quite small.

Remember that lift acts normal to the surface - if you angle the surface, you change the vector resulting in a reduced downwards vector and adding a sideways one.

Looks like a gimmick to me.

While pagani solution is a gimmick, I have a different opinion on zenvo.
IMO there are benefits of this solution, like being able to run softer rear suspension and tires doing less work.

[Just_a_fan]

Yeah. And It's been done.

Pagani Huayra raises it's flaps on the inside to increase downforce on the unloaded tires and prevent roll.

Zenvo has a solution where they flip the whole back wing to achive the same thing.

https://thumbor.forbes.com/thumbor/960x ... it%3Dscale

That wing will cause a small reduction in downforce but it will give an increased lateral force albeit likely quite small.

Remember that lift acts normal to the surface - if you angle the surface, you change the vector resulting in a reduced downwards vector and adding a sideways one.

Looks like a gimmick to me.

While pagani solution is a gimmick, I have a different opinion on zenvo.
IMO there are benefits of this solution, like being able to run softer rear suspension and tires doing less work.

How will this wing allow the suspension to be changed? And how will that equate to the tyres doing less work?

[sosic2121]

That wing will cause a small reduction in downforce but it will give an increased lateral force albeit likely quite small.

Remember that lift acts normal to the surface - if you angle the surface, you change the vector resulting in a reduced downwards vector and adding a sideways one.

Looks like a gimmick to me.

While pagani solution is a gimmick, I have a different opinion on zenvo.
IMO there are benefits of this solution, like being able to run softer rear suspension and tires doing less work.

How will this wing allow the suspension to be changed? And how will that equate to the tyres doing less work?

Since all aerodynamic force is not downforce, peak force that rear suspension sees should be lower, allowing for softer suspension.

Traditionally, DF(together with weight of the car) push the tires into the road to allow higher cornering grip, allowing tires to work harder.
This wing(partly) circumvent the tires, and is working directly on the body of the car.
So tires are doing less, but cornering limit is the same, or higher.

Also, since wings center of load is much higher than cars centre of mass, it should counter weight transfer and some negative effects that it has.

I don't know what DF can this wing produce and what angles can it reach, but it theory I think this concept has potential(unlike pagani which is imo mostly a gimmick)

[Just_a_fan]

Traditionally, DF(together with weight of the car) push the tires into the road to allow higher cornering grip, allowing tires to work harder.
This wing(partly) circumvent the tires, and is working directly on the body of the car.
So tires are doing less, but cornering limit is the same, or higher.

If you apply a vertical load on to the body of the car then you put that same vertical load on to the tyres (spread out over the tyres depending on where the vertical load acts in respect to the centre of mass). You don't "circumvent the tyres".

[Hoffman900]

Traditionally, DF(together with weight of the car) push the tires into the road to allow higher cornering grip, allowing tires to work harder.
This wing(partly) circumvent the tires, and is working directly on the body of the car.
So tires are doing less, but cornering limit is the same, or higher.

If you apply a vertical load on to the body of the car then you put that same vertical load on to the tyres (spread out over the tyres depending on where the vertical load acts in respect to the centre of mass). You don't "circumvent the tyres".

Yeah, wow.

As for Indy, I have to think about it some, but the aero asymmetry could have something to do with asymmetry in the setups of the car, including yaw, which would change the AoA. Same with NASCAR (they put a yaw rule into effect).

[sosic2121]

Traditionally, DF(together with weight of the car) push the tires into the road to allow higher cornering grip, allowing tires to work harder.
This wing(partly) circumvent the tires, and is working directly on the body of the car.
So tires are doing less, but cornering limit is the same, or higher.

If you apply a vertical load on to the body of the car then you put that same vertical load on to the tyres (spread out over the tyres depending on where the vertical load acts in respect to the centre of mass). You don't "circumvent the tyres".

This wing is producing centripetal force which directly counters centrifugal force, so in effect centrifugal force is reduced and tires are bypassed in the process
https://youtu.be/Hvocv9zF10c

[Just_a_fan]

Traditionally, DF(together with weight of the car) push the tires into the road to allow higher cornering grip, allowing tires to work harder.
This wing(partly) circumvent the tires, and is working directly on the body of the car.
So tires are doing less, but cornering limit is the same, or higher.

If you apply a vertical load on to the body of the car then you put that same vertical load on to the tyres (spread out over the tyres depending on where the vertical load acts in respect to the centre of mass). You don't "circumvent the tyres".

This wing is producing centripetal force which directly counters centrifugal force, so in effect centrifugal force is reduced and tires are bypassed in the process
https://youtu.be/Hvocv9zF10c

Yes, that's all great in principle when looking at a static situation. But there are other issues to consider in the whole car's performance.

For example, when the wing pivots, it will affect the base pressure distribution across the rear of the car and that will affect the undercar flow. What will that do to the car's total grip and its ability to corner? After all, if you change underfloor flow then you potentially alter the flow under the nose and thus cause an increase/decrease in understeer.

When the wing pivots, the two sides will see different angles of attack - albeit briefly - and that will affect performance - albeit briefly.

How quickly can the system react? Through a chicane, for example, the car will go from lock to lock to lock in very quick succession. Will the wing react quickly enough? If you can move the wing quickly enough, it will also have a roll-bar effect on the rear of the car - rotating the wing will cause the rear of the car to rotate in the opposite sense. How will that be dealt with in a chicane so that the rear end doesn't become unstable? Active damping could deal with it, but it's another level of complexity. Also, dealing with this will remove some of the alleged benefits of "circumventing the tyres".

If the wing is to be reactive enough, it will need to follow the steering wheel in real time. On the road, that's going to be adding some interesting sideways moments as the wheels follow the road surface - in effect, the rear will be constantly wiggling in response to steering wheel movements. And if you damp that effect then you reduce the ability to react to the steering wheel in rapid direction changes.

And above all else - what does the wing do to help the front end grip? All very well saying you can get lateral load at the rear to help cornering, but if the front is a standard car set up, the front end will lose out and you develop massive understeer.

I'd like to see this car run around a representative track with the system active and inactive and see what the lap times say. Likewise, take it on a real road (in controlled conditions) and see what it does with the system active and inactive.

[sosic2121]

If you apply a vertical load on to the body of the car then you put that same vertical load on to the tyres (spread out over the tyres depending on where the vertical load acts in respect to the centre of mass). You don't "circumvent the tyres".

This wing is producing centripetal force which directly counters centrifugal force, so in effect centrifugal force is reduced and tires are bypassed in the process
https://youtu.be/Hvocv9zF10c

Yes, that's all great in principle when looking at a static situation. But there are other issues to consider in the whole car's performance.

For example, when the wing pivots, it will affect the base pressure distribution across the rear of the car and that will affect the undercar flow. What will that do to the car's total grip and its ability to corner? After all, if you change underfloor flow then you potentially alter the flow under the nose and thus cause an increase/decrease in understeer.

When the wing pivots, the two sides will see different angles of attack - albeit briefly - and that will affect performance - albeit briefly.

How quickly can the system react? Through a chicane, for example, the car will go from lock to lock to lock in very quick succession. Will the wing react quickly enough? If you can move the wing quickly enough, it will also have a roll-bar effect on the rear of the car - rotating the wing will cause the rear of the car to rotate in the opposite sense. How will that be dealt with in a chicane so that the rear end doesn't become unstable? Active damping could deal with it, but it's another level of complexity. Also, dealing with this will remove some of the alleged benefits of "circumventing the tyres".

If the wing is to be reactive enough, it will need to follow the steering wheel in real time. On the road, that's going to be adding some interesting sideways moments as the wheels follow the road surface - in effect, the rear will be constantly wiggling in response to steering wheel movements. And if you damp that effect then you reduce the ability to react to the steering wheel in rapid direction changes.

And above all else - what does the wing do to help the front end grip? All very well saying you can get lateral load at the rear to help cornering, but if the front is a standard car set up, the front end will lose out and you develop massive understeer.

I'd like to see this car run around a representative track with the system active and inactive and see what the lap times say. Likewise, take it on a real road (in controlled conditions) and see what it does with the system active and inactive.

O, I agree with almost everything you said in this comment. I was just trying to say that idea has some potential, unlike pagani who's active aerodynamics is reducing maximum available DF.

Just to mention, this wing is also capable of changing AoA, so it's not much more complex than "other" wings that change AoA,

and moving in two planes allows it to be fine tuned to compensate for some negative effects...

[PhillipM]

The biggest trouble is those semi slicks the car runs on as stock generate more than 1.0mu.

So you would be better just putting the load down directly through the tyres, because they can turn the downforce into more lateral force than directly using the airflow.
More than that, without the twisting mechanism the car would be lighter and the wing could be made more efficient/aggressive in profile without risking stalling as much.

It's a gimmick, at best.

[hollus]

Think in terms of sines and cosines. You barely lose any vertical force, but you gain comparatively much horizontal force (for small angles)

[Just_a_fan]

Think in terms of sines and cosines. You barely lose any vertical force, but you gain comparatively much horizontal force (for small angles)

Again, assuming the nice static diagrams. But cars are not static systems.

[Tim.Wright]

If your tyres have a coefficient of friction > 1 you are better off using the aero forces vertically to load the wheels ans to let the tyres convert that load i to a cornering force.

If your tyres have a coefficient of friction < 1, then you are better off using your aero forces directly as centripetal forces (assuming you can control them well enough to be in-phase with the driver steer movements).

[Just_a_fan]

(assuming you can control them well enough to be in-phase with the driver steer movements).

Which is the key point here. As a road car, keeping steering, wing and tyre requirements aligned is likely to be problematic. Public roads are anything but consistent.

[godlameroso]

It's an interesting question and the way you measure your results has a big influence on the outcome of the investigation.

A change in local downforce doesn't necessarily translate to more lap time, so even if your instruments say you have more downforce, it could be upsetting the balance or it throws the driver off for the time being.