24 replies to this topic

[schuy]

Hello,

A current F1 car weighs 600kg., that we all know.

An un-ballasted F1 weighs a fair bit less.
Has anyone who bought an F1 car ever tried to run it without ballast?

Should be mighty interesting, given that every kilo reduced significantly increases the hp/kg. ratio.

The performance should be startling.

Liran.

[Sir Frank]

Originally posted by schuy

Has anyone who bought an F1 car ever tried to run it without ballast?

I can think of a few in pre season testings to attract sponsors. One obvious example is the Prost team before 2001 season, Jean Alesi braking the lap record at Barcelona.

Probably they have taken out some ballast but how much of it is a close kept secret Id think.
Of course its also possible that they were not underweight but running with other irregularities.

Assuming a linear relation between weight and lap time (which is totally wrong) and calculating with an improvment of 0,3-0,4s/10kg reduced weight + a ballast of 50-100kg one could get an improvement in lap time of around 1.5 - 4.0s, which does not sound too sensational.

[JwS]

Since the ballast is used to lower the CG removing it would probably have a negative affect on the handling. I'm sure it would affect acceleration and braking too. If Renault sees an advantage in going to 111degree v to drop the cg a little, (not to mention all the other little things that are done) then I have to believe that suddenly pulling all of that lead out of the bottom of the car will screw everything up.
Jay

[Aubwi]

I'm sure its not used to lower CG. They just put the ballast as low as possible because a low CG is better, but that doesn't mean the extra weight actually improves performance. It's only there because of the minimum weight requirement. So they make the best of it by putting it in an optimal location.

[JwS]

But, the cars are actually designed with their ultimate cg location in mind, which means they are designed to have the ballast where it is. If you move the CG the suspension will see different loading. You may be able to adjust things to take advantage of this, but you may not, it might require moving suspension mounts etc, who knows? Certainly springs and anti-roll bars would be completely wrong, dampers. Clearly you can't say it doesn't matter where the cg is, they have spent alot of time getting it where it is for a reason. It also affects front rear balance and polar moments.
I recall being surprised at the amount of ballast used, but I cant recall numbers, the only thing that I kind of recall is someone running a substantial plate in the front wing ( for some reason 40 lbs is a number I remember, that seems crazy, but I remember that it seemed crazy when I heard it too)
Does anyone know about how much is used in most of the cars? is the 50-100 Kg right, that is about what I was thinking too.(220lbs!) I believe that is more than the engine usually weighs, that is a huge change.
JwS

[Wuzak]

An F1 car is 600kg including driver, but without fuel (and other fluids?).

So we are talking around 520-530kg for the car itself.

The numbers I have seen for ballast are about the 50-100kg that JwS said.

Meaning that the bare F1 car could be as light as 420kg!

[Peter Morley]

An un-ballasted F1 weighs a fair bit less.
Has anyone who bought an F1 car ever tried to run it without ballast?

Given they have no weight limit in EuroBOSS it is reasonable to assume they run cars without ballast.

F1 teams carefully place the ballast in such a way as to increase the performance of the car, but that is only because they are 'obliged' to use it, if they didn't have to meet the minimum weight they would use less ballast - you can be sure that removing at least part of it will be beneficial.

In the good old days (when some of the current officials were involved with teams) some cars seem to have ran underweight and were then 'ballasted' before the car was weighed (either by topping up the water tank - used for brake cooling for example!, or knocking the nose off before entering the pits and replacing it with one that took several mechanics to carry, etc.).

[Ali_G]

JwS: I doubt the removal of ballast would do anything to the handling if only make it better.

A lighter car would do just about everything good. Sure the C og G might be a bit higher but not by much.

Niall

[Aurelio Lampredi]

From what i know it's better to lower the car's CoG by 2mm than have a weight advantage of 20kg. I know that this seems excessive but i am a fan of this theory...

[Aubwi]

A lower CoG is better because it reduces the weight transfer to the loaded wheels while cornering, braking, and accelerating. But lowering the CoG by adding weight does nothing to reduce the weight transfer, in fact, it can only increase weight transfer, so it can only be a disadvantage.

[Greg Locock]

That is an excellent one line summary

[JwS]

I guess my point is that the cars are designed to have the CG where it is, if you move that without correcting the suspension geometry to optimize the car for this new arrangement you may not see a performance gain. If the rules were changed next year to lower the minimum weight I am sure that the cars would be faster, no question there.
Lets say the CG is currently located exactly at the roll center, therefore no moment due to lateral forces (effectively no weight transfer). If you move it anywhere you have suddenly introduced a new force to the vehicle, and your previously optimized suspension is no more.
JwS

[Paolo]

Aubwi is totally right.

Other effects of running ballastless:

1) Tyres will have more grip ; infact their adherence factor decreases with increasing weight and weight transfer , and viceversa. Improvements around 2-4 % can be expected for the removal of current ballasts.

2) The effect of aerodynamic downforce increases significantly : having , say, 1000 Kg of downforce acting on a 500 kg car is about the same as having 1200 Kg of downforce acting on a 600 kg car.

3) improved acceleration

No competition with a rule-compliant car, really...

[JwS]

Moving the CG of the car, by the placement of ballast or any other method, can reduce or eliminate roll moment. Placing 1/6 of the weight of the car an inch off the ground will significantly lower the cg, if you remove the ballast without compensating you will probably introduce a large roll moment which would load the outside tires and degrade their grip (despite reduced oveall mass). In addition the fore and aft CG shift would screw up the balance further.
End result : an ill handling dog that has a ton of power, if you're in the NHRA that might fly, but I'm not sure it will get you around a road course faster.
JwS

[Aubwi]

Oops scratch that you're right.

I mean about the roll moment. But still, I guess I just don't think it would be a big deal.

Weight is constantly being added and removed in the form of fuel, and the driver just has to deal with the changing handling.

Changing the longitudinal location of CoG might move it back behind the Center of Pressure, which is not good, but I think simple wing adjustments can compensate for that.

[schuy]

Originally posted by JwS
if you remove the ballast without compensating you will probably introduce a large roll moment which would load the outside tires and degrade their grip (despite reduced oveall mass). In addition the fore and aft CG shift would screw up the balance further.
End result : an ill handling dog that has a ton of power, if you're in the NHRA that might fly, but I'm not sure it will get you around a road course faster.
JwS

Are you saying that cars weighing over 600kg. would be faster than those sticking to the minimum weight?


No way jose...

[JwS]

Shuy,
I'm not saying that exactly, I am saying that the cars are designed to weigh 600Kilos, If they designed to the same rules, except 500 kilos, they would definitely be faster, but that is different from taking out the designed in ballast.
The fuel tanks are designed and positioned to minimize the effects on the CG, (they are basically at the longitudinal CG) They do have a big effect as they are emptied, more than just the weight change.
By a extremely rough calculation taking the ballast out could add something like a 700 Nm (500 ft-lb) moment around the roll axis. (based on some best guess dimensions and locations of the roll centers etc.) I don't think that would help handleing too much.

[schuy]

Good point, however I reckon losing ballast, even by a bit, would always improve performance.

Thanks for the information though, made me ponder some things...

[Greg Locock]

Given that the roll centre of many good-handling roadcar's axles moves by something like 200 mm during a 1 g corner, I really think that worrying about cg vs RCH location shifts of the order of 20 mm are almost irrelevant. I'd also add that given the very limited articulation and high rate of F1 suspensions the roll centre location has a very slight influence on the rate of weight transfer - the springs are stiff enough to move forces across the car much faster than the tyres can react. Tyres take about 200 ms to react - so if the natural frequency of the roll mode for the axle is much greater than 5 Hz then for all practical purposes it is fast enough. Given the sidewall depth and low pressure of F1 tyres I suspect they might be even slower than that.


And of course- which roll centre are you talking about? The geometric roll centre? or the force based roll centre?

The only important thing is the effect on the tyres, and as various people have said, the less mass they have to accelerate sideways, the better.

There is a lot of rubbish on the www about roll centres, you'll notice that many of the more authoritative books keep strangely silent about why exactly roll centres need to be where they are. I don't claim to know the answers, but I do know that when you optimise hardpoint locations for best time around a circuit, that you monitor wheel loads, not RC Y and Z for each axle.

There is a fascinating PhD thesis by E(someone) that discusses the meaning of roll centres, the main conclusion from which is that (paraphrasing) "the kinematic and force based RCs differ not only in location, but move in different directions as a result of hardpoint changes, and calibration, and also move diffferently during cornering events". he's being polite, what he's saying is that GRC is pretty much useless. Unfortunately I have lost the reference, but I am trying to find it again. The upshot of this is that if you are going to worry about roll centre location you are much better off back calculating it from the steady state cornering wheel loads than messing about with neat geometrical constructions.

[desmo]

Empiricist

[Fritz]

I think it is important to differ steady state cornering from handling. The ultimate cornering performance of a F1 car should in my opinion always be associated with steady state cornering. Rally cars are ofcourse completely different in that aspect. Therefore, as steady state cornering is nothing more than a static equilibrium and cornering performance is limited by weight shift, it is clear that any weight reduction that does not affect the fore-aft balance will improve performance. You will certainly be able to remove a whole lot of balast without changing the longitudinal position of the CG.
Handling is linked to dynamic processes; turning in, correcting under- or oversteer, bumps, ... It is up to the driver to 'calm down' a car to its steady state asap. I know this is never possible, but I think it is what separates good drivers from very good drivers. A loss in handling due to weight reduction will make it more difficult to obtain such a near-steady-state condition. The car will be faster but the driver might not be able to extract the potential.
It makes me think of Schumacher in his Benetton days. He did 6000 revs with his arms, but he was by a fair margin faster than any of his team mates.
Removing the ballast will certainly make the car faster, but you might need to hire a better driver...

[Greg Locock]

That was the old theory of circuit racing. The driver's objective was though to be to control the vehicle into a smooth transition between a succession of steady state accelerations. However, by 1960 Moss had written that he was experimenting with exploring the edge of the friction circle AT ALL times, in other words the vehicle rarely attained a steady state acceleration, unless it was flat out or on a long straight. He braked up to the apex of corners, and accelerated (gently) as soon as he was past the apex.

However, staedy state accelerations (pure brake or pure WOT or pure latacc) are easier to analyse, and if you can't set the vehicle up for them then it is unlikely to be much good if you are driving at other points on the circumference of the friction circle.

There's a good discussion of this in Race Car Vehicle Dynamics by Milliken.

[Fritz]

Sure, but handling is I believe still linked to more abrupt changes than the almost steady state of following the friction ellipse. Would reduced ballast lead to an undrivable car when you only take into account the smooth weight transitions due to the slow transition from braking into turning into acceleration?
I would think that removing low ballast would have serious impact on the car's behaviour during fast (higher frequency) processes. Such as going over bumps, sudden weight shifts due to loss of or new-found grip, ...
In short, I think that following the friction ellipse can be treated as a succession of steady states, the forces involved are so much lower than these that act during true dynamic behaviour. As such, performance would be linked with static behaviour and any weight reduction would lead to improved performance. Correct me if I'm wrong, I'm a mechanical engineer, but never had a course on vehicle dynamics before.

[Greg Locock]

Hang on, I'm agreeing with you. Removing ballast from the car will usually (well I'd put money on almost always) result in better lap times. I would guess, without doing any calculations, that it will improve the performance of the tyre far more than any notional upset to the roll centre geometry, particularly given the tiny suspension travel seen in an F1 car. I haven't got d (latacc)/d (camber) for an F1 tyre but again Milliken has for a 16 inch tyre and it is only something like 0.01 g/deg, for a 1.1g corner. 1 degree of camber error is rather a lot to be induced by an RCH/CGZ 'mismatch' (it implies one degree of body roll I think, which is heaps in this context)What is the total useable suspension travel on an F1 car anyway? +/- 20 mm? or even less? If it is 20 mm that implies a maximum body roll of 1.5 degrees, so it would be impossible for an RCH mismatch to introduce 1 degree of body roll, given normal geometry. and a 1% reduction in latacc is measurable, but not the end of the world.

Bear in mind that the geometry has to accomodate different fuel loads and I think you'd agree that it just can not be that sensitive to RCH vs CGZ.

If anyone has a lap time simulator, say Fastlap, then it would be interesting to examine the effect on lap time of removing weight from the car at say 50 mm above ground level. I don't have a way of modelling lap times, yet.

Have we beaten this dead horse enough?

[desmo]

I was told two or three years ago that typical wheel travel for F1 cars was around 20-25mm front, 70-80mm rear FWIW.