Downforce Map

[Belatti]

Can someone post some information regarding how does the downforce distributes in an F1 chassis?

[Belatti]

OK, almost 1 month and no answers.
I would appreciate at least a "I don´t know" or a "I think ... but not too sure".

My question is based in some idea that crossed my mind when helping a friend that is in 3rd year mech. eng. solving hiperstatic and isostatic beams exersises.

Would downforce in front of the front axle (generated by front wing) produce "upforce" in the rear and vice versa. Here I´m using the principle of superposition.

So, when downforce is applied in a well balanced car with good air flow everything is ok, but when something (eg. slipstream from a car ahead) disrupts the flow into the front wing, you don´t "only" loose downforce there, but also have and uplift if rear wing is still charging.

Understand what I mean? Any idea?

[Ogami musashi]

The modifications of balance are of course present and modern F1 cars are so sensitive that even when braking (so with pitch down moment) the aero balance is changed and a car can suddently oversteer or understeer.

Being in the wake of someone does the same.

Now i suspect the way downforce loadings are transfered to the tyres is a major and secret subject for each teams.

[scarbs]

I think there is a summary in one of Peter Wrights books. As I recall a rough summary is....

DF

Rear Wing 30%
Diffuser 30%
Front wing 30%
Other 10%

Drag
Rear Wing 30%
Diffuser 5%
Front wing 5%
Other 60% (largely the wheels)

[Belatti]

Here there are some very vulgar pictures to ilustrate my thoughts:

[Carlos]

I don't know anything, well not much anyway... but some of the aero threads mentioned this... something about a centre of aero along the length of the car ... sort of similar to a physical center of gravity... theres a center of aero effect... maybe skim the aero threads and PM our knowledgeable residents.

Just spent a few minutes, all I have right now, its called 'aerodynamic centre of pressure', most stuff app to airplanes, can't find anything on cars or as they call them... ground vehicles...

This is a narrative -
http://en.wikipedia.org/wiki/Center_of_pressure

This is NASA Odds And Ends
http://stinet.dtic.mil/oai/oai?verb=get ... =ADA056468

http://wright.nasa.gov/airplane/ac.html

http://www.grc.nasa.gov/WWW/K-12/airplane/cp.html

All the time I've got Belatti... Life and Lucre interfere with my habitual hobbies

[Belatti]

scarbs: thanks, I suspected some values cause of racing sims, you increase FW angle and you gain grip but no too much drag!

Carlos, thanks for the links and your time , I studied some of that in fluids mechanics and it is always good to have a look at them again! But as you said, it happened the same to me: a lot about planes and nothing about cars

Ogami, could we be chating about one of the biggest mysteries in F1 design?

In resume: Thank you all a lot!

[Ogami musashi]

Belatti, i don't know how it is done, but downforce is net force which means it is an apparent weight (this is a major advantage of the downforce) so it is a short range force.

That means it only acts on surfaces and then propagates through body via all the super complex mechanical.chemical.mystical laws to the tires.
the tires being themselves hyper complex in their mechanical.chemical.aerodynamical.mystical behaviors.

So, you can produce 2 tons of downforce if you want, the fact is that this acceleration is lost when transitioning into the chassis and then tires this is a problem.

And there i wish for Carlos to pop up in the thread with his magic links to pdfs that will help us!

[Carlos]

Ogami musashi- A reseach task beyond my abilities. However this article offers some tantalizing suggestions, not a complete answer, the two questions of mechanical grip and aero downforce have been treated separately but in relationship to each other in Mosley's Equations.

http://atlasf1.autosport.com/99/san/pre ... ensen.html

[dumrick]

Yes, if you know the center of pressure, you can calculate its influence in wheel load the same way as with the CG. But this is the "sum" of all loads, any specific load behind the rear axle e.g. will load the rear axle and unload the front.
For common street cars, you can take one single measure from the wind tunnel and use it to evaluate and place this CP, is a good enough estimate. For F1 design, however, you must go in detail and understand that, varying the conditions (speed, wing algles, wind, yaw angle, being in the wake of a competitor...), the different forces vary, resulting in the CP moving all the time, thus the load in any wheel. Any distance between the CP and CG placements also causes a moment relative to the CG, possibly causing the vehicle to pitch, dive...

[Ogami musashi]

Yeah, i think it is more efficient in F1 to calculate each wing/underbody CP rather than the overall one (except for the stability you mentioned).

But overall i think engineers not in the set up part (in which they would use the Cp method) but in the conception look also of tribology that is the internal friction that decreases the load transfert of downforce.