On which side is downforce more effective?

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godlameroso
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On which side is downforce more effective?

Post by godlameroso » Sat Apr 14, 2018 8:38 pm

Is downforce more important on the loaded or unloaded side of a car during transient maneuvers? Say in turn 8 around Shanghai, the long mid speed right hand, would you gain more in the corner by having more downforce on the right side or left side of the car?
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Tim.Wright
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Re: On which side is downforce more effective?

Post by Tim.Wright » Sat Apr 14, 2018 9:08 pm

From a grip perspective you will benefit more from loading more lightly loaded wheels which will usually be the inner wheels. Tyres have a coefficient of friction which drops as you increase their vertical load.

From a balance perspective it's difficult to generalise. A laterally offset downforce will cause a lateral load transfer which causes symmetrical effects like toe and camber to create net lateral force which could change the balance.

Additionally you should consider that if the downforce can be asymmetrical (which I'm sure it is) then so is the drag. A lateral drag offset will cause an US/OS yaw moment depending on which side it acts.

I could imagine an ideal situation would be to create downforce on the inner wheels and drag towards the outer wheels to in function of the sideslip angle. Difficult to imagine how to implement this though.
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bill shoe
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Re: On which side is downforce more effective?

Post by bill shoe » Sat Apr 14, 2018 9:08 pm

I think a given amount of downforce would be more effective on the inside (lightly loaded) side of the car, because tire lateral force (normalized to vertical force) declines at higher loadings. Also would heat and wear the tires more evenly.

Edit: a.k.a. what Tim said.

Vanja #66
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Re: On which side is downforce more effective?

Post by Vanja #66 » Sun Apr 15, 2018 9:30 pm

Outboard car side in corner is closer to the ground, no matter how stiff the suspension is - tyres flex. Being closer to it makes more downforce on that side and it would be great to have it evenly distributed or even more on the inner side of the car. That's why active suspension and all those recently banned "trick" suspension set-ups are/were worth investing into. :)

JonoNic
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Re: On which side is downforce more effective?

Post by JonoNic » Sun Apr 15, 2018 9:36 pm

Well negative camber allows the outside wheels to run square during hard cornering. So aero on the outside would do the same?

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Re: On which side is downforce more effective?

Post by Jolle » Sun Apr 15, 2018 9:38 pm

Extra load, trough balance, active suspension or downforce (any other then mass) is always best welcomed at the wheel that will loose grip the earliest, so, the outside wheels. Outside front for turn in, both outside wheels mid corner and rear outward wheel corner exit.

Tim.Wright
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Re: On which side is downforce more effective?

Post by Tim.Wright » Sun Apr 15, 2018 10:30 pm

Jolle wrote:
Sun Apr 15, 2018 9:38 pm
Extra load, trough balance, active suspension or downforce (any other then mass) is always best welcomed at the wheel that will loose grip the earliest, so, the outside wheels. Outside front for turn in, both outside wheels mid corner and rear outward wheel corner exit.
In my experience, looking at both wheel force sensors on actual cars and simulated forces in mathematical models, the inside wheels drop off their cornering force well before the outside. They are essentially sacrificed on purpose using load transfer and geometric effects to ensure that the outer wheels (which produce the dominant cornering forces) produce grip as long as possible.
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Sevach
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Re: On which side is downforce more effective?

Post by Sevach » Mon Apr 16, 2018 2:10 am

I've always wondered how a assymetrical Indycar would perform (setup is already assymetrical).

Scootin159
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Re: On which side is downforce more effective?

Post by Scootin159 » Mon Apr 16, 2018 2:30 am

Indy cars already run asymmetric aero on some ovals. In particular in Indy 500 qualifying, it's not unusual to see them have more wing on the inside of the car than the outside. Further evidence that having extra downforce on the inside (as well as a slight drag force rotating the car) would be better than the inverse.

trinidefender
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Re: On which side is downforce more effective?

Post by trinidefender » Mon Apr 16, 2018 4:09 am

Vanja #66 wrote:
Sun Apr 15, 2018 9:30 pm
Outboard car side in corner is closer to the ground, no matter how stiff the suspension is - tyres flex. Being closer to it makes more downforce on that side and it would be great to have it evenly distributed or even more on the inner side of the car. That's why active suspension and all those recently banned "trick" suspension set-ups are/were worth investing into. :)
In all practical applications to do with F1 then yes but just to be a smartass :D I'll remind you that if you have your roll centre above your centre of gravity then your car will actually roll toward the inside of the corner.

Vanja #66
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Re: On which side is downforce more effective?

Post by Vanja #66 » Mon Apr 16, 2018 10:07 am

trinidefender wrote:
Mon Apr 16, 2018 4:09 am
In all practical applications to do with F1 then yes but just to be a smartass :D I'll remind you that if you have your roll centre above your centre of gravity then your car will actually roll toward the inside of the corner.
Cheers to that! :D

But as Tim said, in practical applications the outside front wheel is always more loaded, so there's no denying how cars roll in reality. :) Formula Student cars in general have pro Ackermann steering, but only because of very low cornering speeds and low vertical loads as far as I know.

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Re: On which side is downforce more effective?

Post by Andres125sx » Thu Apr 26, 2018 3:41 pm

Tim.Wright wrote:
Sat Apr 14, 2018 9:08 pm
Tyres have a coefficient of friction which drops as you increase their vertical load.
Is this correct Tim? I know you know what you´re talking about, but this makes no sense to me so I have to ask just in case it was a mistake while typing. If it´s not a mistake and that´s correct, may you elaborate?

Maybe that´s only on a perfectly flat surface? Tarmac is far from flat so in my mind when a tire load is increased, rubber should get into the holes deeper, increasing friction

:?: :?:

Tommy Cookers
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Re: On which side is downforce more effective?

Post by Tommy Cookers » Thu Apr 26, 2018 4:24 pm

(1) if the coefficient of friction doesn't vary with vertical load the friction (force) is proportionate to vertical load increase

(2) if the coeff of friction falls with load increase but in a smaller proportion the friction force has still increased with load
but the increase in friction is less than case (1)

ie the tyre is less 'efficient' at high loads

I thought

Tim.Wright
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Re: On which side is downforce more effective?

Post by Tim.Wright » Thu Apr 26, 2018 5:42 pm

It's basically what Tommy said. The frictional force increases yes but the coefficient of friction decreases (they are two different things)

The coefficient of friction is the instantaneous slope of the available friction force when plotted against the vertical force. The frictional forces increase regressively with vertical load. It's roughly an inverse parabola. Theoretically there will exist a force at which increasing the vertical won't give you anymore grip force.
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dren
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Re: On which side is downforce more effective?

Post by dren » Thu Apr 26, 2018 5:48 pm

Wouldn't your tire contact patch increase with vertical loading since the tire is flexible?
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