F1technical.net

Reca, thank you very much. We have been enlightened, oh, master.

What a beautiful post! You made me smile with "Both these things not really easy to achieve..."

You made me pause for a while, to "get" why the moment caused by pressure counteracts the one originated in braking. I never thought about it, but thinking about the car as an "inverted wing", surely it has to be high. You have to wonder how high it can be, given the low pressure under the diffusser, the high drag and the bulky rear shape.

Is this the reason (well, one of them, just look at the tires) why the rear wing is located higher than the front wing (besides aerodynamic shape)?

The inffluence of this "drag" torque must be high, enough to throw your calculations off... or am I wrong? The car is pretty "asymetrical" in this sense.

BTW, what I like more about the post is that you show how closely related are a "simple" thing, like an acceleration profile and the mechanical properties of the whole car. I've been trying to learn as much as possible about the software you pointed me to. I wish every road designer understand it. At least, I must find the time to grasp it.

Anyway, beyond your impressions of GP and F1 cars, Nelsinho comments (in F1tecnical news) seem pretty enthusiastic.

Thanks Ciro and NickT.

Actually reading again my post I noticed a mistake. I said that body movements add a further weight transfer while that’s wrong, the one calculated with the basic geometry data (Cg position and wheelbase) is the total one (otherwise it wouldn’t make sense to calculate it as I did...), it could change a bit due to variation of position of the cg related with body movement but that’s a minimal variation. What the suspension geometry and springs/shocks stiffness affects is mainly how fast the load is transferred (obviously also body inertial characteristics matter on that), with no dive and no squat it’s transferred instantly.
While talking about roll the suspensions (relative stiffness front/rear) have an influence also on the distribution of the total weight transfer between front and rear.
Sorry for the mistake, didn’t think enough about it while writing.

Ciro Pabòn wrote: The inffluence of this "drag" torque must be high, enough to throw your calculations off... or am I wrong? The car is pretty "asymetrical" in this sense.

The reason I didn’t care much about it is that my main point was to establish a “maximum” for the weight transfer (seeing that it was suggested it reached 80% at the front and that looked way too much) so once I noticed that that drag moment would have reduced it and not having data about an approximate position I just neglected it.
If I had to guess a position I would say that it shouldn’t be particularly high because, even if rear wing is quite high, still the biggest part of drag is related with tyres, car body and cooling, and that’s particularly true in Monza where the rear wing is tiny.
so if I had to guess I would put an ideal centre of pressure at wheel axle height or thereabout.
Assuming it’s at 0.4 m above the ground (a bit higher than wheel axle) that’s the result (purple is the previous one without drag force) :
[IMG:150:128]http://img177.imageshack.us/img177/4053 ... nz1.th.jpg[/img]
As you can see it reduces the peak by roughly 3% and acts mainly (expectably) at high speed.

Anyway I think more about it and look for some data to see if I can improve the approximation.

I feel almost guilty by interrupting this wonderful and warm thread. It's truly a pleasure just to have any kind of association with so many enthusiastic and nice people.
In the discussion of braking and anti dive and such, there are many different forces at play, causing and reacting to different inputs. Myself, I make a mental picture of a side view of a Formula One car, and draw little lines. There are certain points, such as tire contact patch (where at the end of the day, all the forces pass through), center of gravity, center of aerodynamic downforce, center of aerodynamic drag, to name a few. Of course, this all can be visualised by simple trigonometry. Force vectors, and the resulting forces. And as I said before, and this is very important, different laws of physics and forces from different sources. Mass, center of gravity, inertia. Aerodynamic drag and downforce. The torque from the drivetrain, the rear wheels attempting to lift the nose on acceleration and the front wheels trying to raise the rear under braking. Then there are the suspension mounting points and the fundamental geometry of the suspension. The torsion bars, their loads, where they are mounted, and act upon. Tons and tons of different lines, but each one having an effect on how the car reacts.
One good example is under braking, where the brake pads grip the disks, which apply a (negative) torque to the suspension, and could make it rise or dive depending on the geometry. Then there is the center of gravity, and all that mass. The car still wants to keep moving forward, but the force on the contact patches of the tires apply a leverage. And then the wings, having virtually no mass, but pressing hard down relative only to the velocity of airflow. The wing doesn't care if the driver is on the gas or brake, it just wants to push down.
Whew, it's late here in the great White North, and I'm doing the late night vigil to watch the qualifying. My head is already spinning. My rant is just to try to point out that when discussing this stuff, we should try to identify and separately categorize each individual force, and what it does to the rest of the car. Yea, it is complicated, but only if you try to digest it all in just one bite (hmm, reminds me of one of my favorite sayings.... how do you eat an elephant? One bite at a time... )
A Formula One car is a wonderful ballet of mechanical interaction, designed for a brutal attack on the laws of physics, resulting in a complicated, but gorgeous display of beautiful motion. Hmm, so is a blonde in a bikini on a hot beach... my mind digresses.

How about hydraulic motors on each wheel? It would still be as dangerous as electrical wires to motors, but if we every hit a chipmunk at speed, at least it wouldn't expire in a flash of light.......? lol
Why not have the driver sit facing backwards since the force of braking is higher than acceleration? Just use lots of mirrors and have a monkey motion steering system. Of maybe have the cockpit roll with the G's?
Under braking have the rear wing unfold like a wind generator, and flash subliminal messages to the spectators? Buy Shell, buy shell, buy shell, I love Max.. lol.
I'll sign off for now, it's time to locate my center of sanity and watch the qualifying. Peace all.