Underbody Tunnels

[xpensive]

flat floor is not particular sensitive to rear rideheight changes in downforce ,as long as you do not get into nose up configurations.

for a sweep of rear ride height settings with a set front rh of 33mm
you would get 699KG @3mm,845kg@13mm,904kg @23,927@33,916@43 and 891@53 for example .

so dramatic ride height changes of 20mm from 23 to 43 will yield only a difference of 10 kg of downforce , apparantly no rake at all will give best downforce.

BUT changing front rh will still give you best downforce at 33 to 43 mm rh at the rear....and the optimum configuration would be 3mm front rideheight ...but now resulting in 1056kg ....

Being a sucker for hard numbers myself, occupational damage that, I love seeing someone trying to get ballpark values.
I would like to give you a few suggestions if I may, in order to make your presentation a little easier to follow?

- Try to begin with xplaining the conditions of the xample given, like in this case; If the object is a road-vehicle or just a flat surface, what does it look like on the top, surface-area and air-velocity, any rear venturis, that sort of thing.
But perhaps most of all, what method was used to crack those numbers?

- Take your time to organize the results in a comprehensible way, easy to read.

- It might be a good idea to stick to SI-units, kg is mass and could be misunderstood.

[marcush.]

flat floor is not particular sensitive to rear rideheight changes in downforce ,as long as you do not get into nose up configurations.

for a sweep of rear ride height settings with a set front rh of 33mm
you would get 699KG @3mm,845kg@13mm,904kg @23,927@33,916@43 and 891@53 for example .

so dramatic ride height changes of 20mm from 23 to 43 will yield only a difference of 10 kg of downforce , apparantly no rake at all will give best downforce.

BUT changing front rh will still give you best downforce at 33 to 43 mm rh at the rear....and the optimum configuration would be 3mm front rideheight ...but now resulting in 1056kg ....

Being a sucker for hard numbers myself, occupational damage that, I love seeing someone trying to get ballpark values.
I would like to give you a few suggestions if I may, in order to make your presentation a little easier to follow?

- Try to begin with xplaining the conditions of the xample given, like in this case; If the object is a road-vehicle or just a flat surface, what does it look like on the top, surface-area and air-velocity, any rear venturis, that sort of thing.
But perhaps most of all, what method was used to crack those numbers?

- Take your time to organize the results in a comprehensible way, easy to read.

- It might be a good idea to stick to SI-units, kg is mass and could be misunderstood.

ok .
on one hand you suck for numbers .I provided those.
On the other hand you seem not happy that I intentionally left out some detail as it is already difficult to capture without having a graph showing the tradeoffs.

As for the KGs ,yes that is a obvious glitch ,but quite normal ways of communication in the field ... to me a kilogramm catches my imagination better than 10N but obviously you are right there.

I can of course provide the conditions for these data ,but in fact it would not really help ,as this is valid only for those conditions and that car.so what?
My only intention was the statement:set up rake has to be 20 mm for a flatfloor car is not necessarily true ,and what you need is the knowledge which rake and rh
you really need dynamically and how you get there.
As with increasing downforce you will squash the tyres and springs more ,so additing springrate will put you in a different area of the aeromap....so first step for any underbody aero car is to measure dynamic rideheights during all your tests and draw your conclusions (building up an aeromap)from this .So on your outing loading down the ride heightdata (not only suspension movement!)you will instantly see if and how long you are in a prefered area of your aeromap when it counts.From there you can decide how to get the car in the window for longer .

ah..by the way .my example does not even account for front rear split ,just total
value so in effect the hard data is not really more than examle and it was meant to be just that.
the available conditions for the example are: 240km/h,15°C,1bar

[xpensive]

Just trying to help, giving numerical results without adequate input-data the way you do is engineering-wise useless.

[marcush.]

Just trying to help, giving numerical results without adequate input-data the way you do is engineering-wise useless.

It was not meant to be a table to be applied to a diffrent car.
the information of conditions would as weel not be helpful by any means in this .

again the statement rake of 20mm static is not necessaryly a good starting point to aquire knowledge abbout the aeromap.dynamically the vehicle could do anything from nose up to rake of 50 mm dynamically ,so without a doubt withot full knowledge of setup,charcteristic and aeromap a precise starting point for the tradeoff is just not possible.
What is possible ,and this was exactly the starting question ,is there a general
tradeoff in terms of rideheight vs CG height implications andf there you could clearly state :
at the rear your deciding factor is the mechanical side of things is the mmain objective ,as the flatfloor is not overly sensitive to rear RH change.

[Belatti]

Your example was OK to me marcush, dont bother yourself.

See, in these kind of questions the only thing that matters is qualitative data. And I got that.

This Xpensive guy wants to turn it all in a scientific matter, and that is useless.

[Giblet]

If aerodynamics was an exact science, and not equally part black art, all the cars would look exactly the same, as there would only be one right answer.

[xpensive]

That's not really the point, more like when you present three-digit numerical values, an Engineer might be led to believe that there was a scientific-like method behind, along with the pertinent input-data to go with it.

[marcush.]

I would not at all call a plot of measured up values very scientific ,in fact it is just empirical data ,and I doubt it makes sense to lay all details on the table
as neither you or me will run that car in that configuration ever.
As we all know ,we very rarely are able to control the variables in testing ,so to read more into it ,like you did is just a useless exercise as only Belatti has even seen the vehicle let alone has made the impression that he has all information available ,nor a possibility to do so.
On the other side the general ways to work on aero optimisation are valid and in case of a flat floor car THE KEY to constant sucess ,as from track to track you might need to adjust static ride heights in the front or springs just to mbe able to drive the thing around (extreme example Nordschleife).So to know where you want to be with the car dynamically and to have the information available where you actually are is going to help tremendously with setup,no matter if your downforce was 9700N
or 9565N at 17°C ....
To further elaborate ,ambient temps are not really that important compared to track temp when it comes to underfloor downforce.As a matter of fact high track temps will
cause the car to drive thru exeptionally hot temps and this is one reason why cars loose a lot of downforce at elevated temps and more so at the frontend.... but try to quantify this ...if you can ,I´m sure after having digested the firesuit ,USF1 will take you on board as Aeroguru and will inevitably perform a BRAWN in 2010...