Drag while cornering

[Ogami musashi]

Dear members,

I'm relatively new to the world of auto racing and went to it by growing interest in formula 1.
I come from the military aviation world.

While browsing the downforce topic on racing cars i went to do comparison with fighter planes.

While turning the main obstacle of faster turn rate for a plane is the induced drag at first then also profile drag for some %.

I asked myself, is it the same with cars?

In fact while comparing former group-c/GTP/sports 3.5l levels of downforce with today F1 cars ones i couldn't answer why those prototypes cars that had for some about twice or three time the level of downforce of F1 cars (some having only 250kg more) and equivalent if not better L/D ratio, didn't match the F1 cars times around a track and especially in corners where they couldn't beat the 5+G lateral acceleration possibilities of today f1cars.

One explanation i thought about, was maybe that the vastly superior power/weight ratio of F1 cars allowed them to go faster in corners.


Any idea?

Thank you.

[phoenix]

Originally Posted by Ogami musashi

Dear members,

I'm relatively new to the world of auto racing and went to it by growing interest in formula 1.
I come from the military aviation world.

While browsing the downforce topic on racing cars i went to do comparison with fighter planes.

While turning the main obstacle of faster turn rate for a plane is the induced drag at first then also profile drag for some %.

I asked myself, is it the same with cars?

In fact while comparing former group-c/GTP/sports 3.5l levels of downforce with today F1 cars ones i couldn't answer why those prototypes cars that had for some about twice or three time the level of downforce of F1 cars (some having only 250kg more) and equivalent if not better L/D ratio, didn't match the F1 cars times around a track and especially in corners where they couldn't beat the 5+G lateral acceleration possibilities of today f1cars.

One explanation i thought about, was maybe that the vastly superior power/weight ratio of F1 cars allowed them to go faster in corners.


Any idea?

Thank you.

Looking at cornering speeds alone, whilst drag may come into it a little, power to weight in the corners really doesn't, so I suspect the answer lies in the relative weight of the cars and the tyres.

Minimum weight of a current LMP1 is 925 Kg whilst F1 is 600 Kg including driver! So there is much more weight to multiply by the cornering forces.

Tyres in prototype racing are expected to last 500Km or more. In F1 you get three sets of tyres for around 320 Km, so tyres for the prototypes have to be harder (as each tyre has to last five times longer) and therefore give less cornering grip despite some extra downforce.

All in all cornering Gs will have to be lower for a heavier car with less grippy tyres, so I think that is the explanation for lower Gs in cornering.

Acceleration will be lower if the power to weight ratio of the prototype is less than F1 and braking distances will be greater in prototypes because of more weight and less tyre grip, as mentioned above. So overall lap times will suffer compared with a formula 1 car despite lower drag. Top speeds on long straights can be much higher than F1 though!

[Ogami musashi]

Thank you for your answer.

In fact the protos i thought about were the sport 3.5L (for example the peugeot 905) that weighted 750Kg and had about 650/700 hp.

Routinely those kind of cars (and their GTP counter parts) had already 2500 kg of downforce at only 280km/h, some of them culminated at more than 4500 kg at 320 km/h!

By comparison nowadays, an F1 car may have 1500kg at 320km/h.

L/D ratio used to be low for F1 cars of the 94-99 area (about 1.5) but those years the L/D have increased a lot to settle at 4,5 average.


The former 3.5/GTP cars had about 5 sometimes 6 max L/D too.


But your remark on tyres makes sense, just that..in fact 3.5L cars were more of a sprint type of racing, they did le mans of course, but routinely the World Sports Car Championship featured 500km races.

Interestingly the peugeot 905 did lap at suzuka 92 (in practise) 1.43' just 2 seconds slower than Senna the same year!

But compared to today's F1 car the lap times did fall by more than 10 seconds (qualifying about 1,29' and in race 1.31' for 2006).

Also, at le mans 92, the peugeot 905 did in qualifying a 3.21' lap , 7 seconds faster than the next opponent (the toyota) but thoses cars were T-cars, that's cars specially designed to do qualifications.


All in one,the tyres reason is okay to me (just as the engine revs) but still i wonder why that downforce hell did not translate in more radical lap times.

This question soars also in the wake of the 2009-2011 F1 regulations that states no more than 1250Kg downforce is to be generated at any time by an F1 and still FIA assures lap times will be similar to thoses that we have now..

There's a key relation between the downforce needed, how it is used and lap times that i still don't get clearly.

[Goran Malmberg]

A few guesswork from me. In addition to the tire influence.
The downforce must be compared in relation to car weight.
The downforce created at actual corenring speed.
The LMP cars have restrictions for bellypan shape and maybe the downforce
comes more from wings etc.
At what speed does these car create the highest cornering G?
Goran

[Ogami musashi]

Hello,

For the weight we compared it already, if we take a figure of 260km/h a 650 kg F1(assuming the fuel weight) will make about 1500 kg of downforce.

Same speed, a 800 kg (same assumption, 750kg+fuel) peugeot 905 will make 2500 kg of downforce.

Now in fact one very good hint given by you two in the tyres and actual DF while cornering brings a question:

Let's say a 650kg at 250km/h corners at 5Gs (like in silverstone, magny cours ...) how much downforce is needed?

I think that if we go into that we will see many clues about why a sports car can't match a modern F1.

Both of you argument (tyres compound, and real downforce exerced in corners) will fill into all the parameters but i don't know all of them.

[AU N EGL]

Does not the current F1 cars have the most downforce or Drag of any racing car?

and does not downforce have a lot to do with the aerosetting of the wings? Greater angle of attack of the wings the more downforce, but less top speed.

So circuits that have lots of corners and few long straight would require more downforce of the wings then a ciruite with long straights that requires higher top speeds?

So in short there is no one setting. Each car is set up for the ciruite they are racing on.

[Ogami musashi]

I think you misunderstood my message,maybe it was not clear(i do think so).


in fact i'm looking at physics of cornering with F1 cars.

What is the downforce needed for a given turning acceleration(a G), how this downforce applies on the wheels, how the wheels transfer the pressures to the ground and how all this translates into lateral acceleration...well in fact,physics of cornering.

[zac510]

You need a book, not an internet forum. Start with Milliken and Milliken for vehicle dynamics and Katz for aerodynamics. Get back to us when you've finished them

[Ogami musashi]

Hey zac, you're here also hehe.

Yes i do plan on buying those books but you know sometimes even in great books you don't find the anwer, so unless you assure me that i'll find in thoses books the answer to my question, i think i'll wait, just as i'll keep on thinking that maybe on this forum someone can answer even if you think the contrary.

[Goran Malmberg]

There are allways a number of things that influence cornering power, that will keep this sort of discussion going. We may short everything down to four points of rubber area in contact with the ground, loaded by a force from mass and aero. The load in relation to contact area will create a µ number for the rubber (in question) that will tell how much sidway load it is capable of handle before sliding. F1 or LMP makes no difference. Laptimes are a different matter.
Regards
Goran Malmberg

[Ogami musashi]

Okay thank you.

What do you mean by laptimes being a different matter?

[Goran Malmberg]

Laptimes and cornering capacity must be looked at separatly. There are more factors of influence around the track.
At first glance the number you show may look strange, but I shouldnt take everything for garanted. To sort it out we must take a closer look at those cars to see what happen, which is not possible. However, grip is closley related to the load of the contact patch.
Regards
Goran Malmberg

[Ogami musashi]

Yes you're right, i need to separate things.

I would be safer to compare cornering abilities of both cars only.
Then after if possible look at other parameters (max speed, accelerations and so on).

Thank you.

If number seems odd, mulsannecorner has in its aero database numbers for some GTP cars, i took the 150mph number on purpose, the 200 mph being theorical for some.

[AU N EGL]

As much as we would like to break things down to the simplest form, that is not always possible. Multi factors always come into play.

Tires: what compound, how many laps on the tires or are they stickers?

Track conditions and time of day. Cold tracks are slower then warm tracks and hot tracks the cars stick too much that can not go as fast, or Very Hot tracks makes the corner greesey and the cars slide no matter what.

Engineers for the tire companies do the best that they can with differnt rubber compounds, test the tires, retest the tires.

Aerodynamic engineers with all the wind tunnel testing, changes here and there.

Supenssion enginers - different suppension set ups work on differnt tracks.
Sebring is very very bumpy, not un common to see cars skip and bounce around some Sebring corners. Other tracks are very smooth.

( part of the reason why teams and manufactures like Sebring they way it is. It is ruff, bumpy and very demanding on equimpent.)

Then all this infomation and technolgy is put together and handed over to the Test drivers. Thousends of miles or KM are logged. Reajustments are made.

Car is handed over to the race drivers, for the Race. The real test.

Almost every team manager will tell you, It comes down to Luck.

[Goran Malmberg]

Originally Posted by AU N EGL

As much as we would like to break things down to the simplest form, that is not always possible. Multi factors always come into play.

Agreed. Multifactors is one big problem in moost discussion, especially the quantities of influence of one and each of them. Both the question and the answer must be specified and detailed.
If we for example talk how to cure over-understeering, we might not even agree about what we mean by the term. Not to mention the number of "multifactors" for a cure.
Goran Malmberg

[phoenix]

Originally Posted by Goran Malmberg

Agreed. Multifactors is one big problem in moost discussion, especially the quantities of influence of one and each of them. Both the question and the answer must be specified and detailed.
If we for example talk how to cure over-understeering, we might not even agree about what we mean by the term. Not to mention the number of "multifactors" for a cure.
Goran Malmberg

Perhaps there are ways of simplifying - here is a suggestion but I'm not sure if it is valid:

IF tyres are taken as the same on both types of car, with front and rear track identical, suspension geometry identical, c of g identical, roll centres identical, roll stiffness identical, and un-sprung weight identical wouldn't the car with the greater downforce : static weight ratio have the greater cornering power?

[Goran Malmberg]

Originally Posted by phoenix

Perhaps there are ways of simplifying - here is a suggestion but I'm not sure if it is valid:

IF tyres are taken as the same on both types of car, with front and rear track identical, suspension geometry identical, c of g identical, roll centres identical, roll stiffness identical, and un-sprung weight identical wouldn't the car with the greater downforce : static weight ratio have the greater cornering power?

I should say that downforce is the key factor for cornering power, concerning rubber coeficient of friction that get less from higher load dont nearly outweight the total friction gain from downforce. So, we should relate the friction number to the mass of the car. Therfore, if we have the same total load (downforce and chassis weight) on the tire contact patch, the example with higher % of downforce will corner faster.

I guess that much of the problem using "simplifying" is that the discussing people must be on the same understanding line of what is beeing discussed.
Regards
Goran Malmberg

[AU N EGL]

Originally Posted by phoenix

Perhaps there are ways of simplifying - here is a suggestion but I'm not sure if it is valid:

IF tyres are taken as the same on both types of car, with front and rear track identical, suspension geometry identical, c of g identical, roll centres identical, roll stiffness identical, and un-sprung weight identical wouldn't the car with the greater downforce : static weight ratio have the greater cornering power?

With the same driver, weather and track conditions, YES.

But that is NOT racing. If one wants evething as close to being the same as possible, watch NASCAR.

[phoenix]

Originally Posted by Goran Malmberg

I guess that much of the problem using "simplifying" is that the discussing people must be on the same understanding line of what is beeing discussed.
Regards
Goran Malmberg

Nicely put - and very apt - as not everything in the Racing Technology threads are about racing per se - they are often about satisfying intellectual curiosity and broadening understanding of basic principles.

[Ogami musashi]

I think in this case, we could look for what differencies there're in weight distribution, suspension geometries , downforce balance and tyres types between a F1 car and a sportscar proto of the group C area?

[johnny yuma]

Random thoughts-

perhaps there can be a relationship between Power to Weight ratio and corner speed in that downforce is not a "free" force it must be provided by the engine.Wind resistance is one of those exponentially increasing things,and the frontal areas of sports prototypes are greater than F1,and the prototypes obviously have more aggressive wings.By the time you are pushing air out of the way at 250 kmh during cornering the tyre to track friction,frontal air resistance and wing drag must be sapping vast amounts of power,and this is one thing F1 HAS PLENTY OF,Apart from better overall aerodynamics AND less weight.They would have to be able to put the power on earlier,and have more to use when they do.THAT is what laptimes are all about.

[Ogami musashi]

Interesting, Downforce/drag ratio were higher on protoypes (about 6, compared to nowadays 4-5 for F1) according to mulsannemike.

I don't know however if those ratios concern only the downforce surface and their associated drag (induced and/or form drag) or the whole car drag.

In fact, as thoses prototypes had the same kind of top speeds as nowadays F1 maybe, if someone had lateral G forces ratings for those cars we could have a comparison, because, as pointed earlier, we should not confuse facts:

F1 cars are faster on a lap time, so i deduced (quite wrongly) they cornered faster as the top speed is about the same, but the acceleration and braking figures are unknown for group C cars so i don't know.

Does someone has some data on cornering forces of group C cars?

Now about the drag in corner, i think the yaw angle plays a role and profile drag in its lenght /span distribution in my opinion does play another role.

When cornering the nose of an open wheeler may offer less resistance and maybe less perturbations, and maybe the front splitter of group C cars was not as efficient as a simple wing?
(under yaw conditions).

[Notso Swift]

I seem to remember an old Autocar that had some corner speeds and G forces comparing F1 and (I think) the Silk Cut Jaguars, so around the early 1990’s. There were most definitely types of corner that the sports cars were faster though, despite being a fair percentage behind on the entire lap. There may have even been info on a Touring car and a road car as well. Normal, gimmicky sort of glossy magazine stuff. This was before you could buy a cheap data logger with all this sort of information readily available.

[Ogami musashi]

really interesting. Do you remember the type of corners? (i presume fast long curves as the downforce produced at high speed was phenomenal).