I just read this in the Merc Silverstone preview.



It got me wondering if their difficulties have something to do with the lack of a sophisticated simulator. I believe that McLaren have the best simulator technology in the business and I also read that Merc/Brawn simply do not have anything comparable in this department. Renault is supposed to be good and Ferrari probably have caught up since they went through a painful season in 2005.

I also read some time ago - probably two years - that McLaren do special surface scans of each track by running a saloon car there with a measuring unit. Eventually I came across a comment about tyre heating in the RC thread about mass dampers.

When I put all this together I conclude that top F1 teams invest a lot of simulation time into optimizing their suspension design and set up for each race. Mercedes probably cannot do this due to a lack of simulator technology. Is this why Brawn have struggled with tyre heating last year and Mercedes is still suffering from one lap/low fuel performance this year? Can anybody give me some feedback on that?

Does dampers really have that much to say on the tire heating?

I believed it was more down to the amount of camber, caster and toe that worked the tires. perhaps something with the chassie roll as well.

The combination of baloon tyres with ultra stiff springs (to maintain attitude and altitude for aero) means the tyres are doing a lot of the suspension work.

I guess there is also a big influence on how you set the combined damping of the J-damper and the two conventional shocks.

Exactly.

So what Merc needs is a leading figure in vehicle dynamics and tyres who can bring them up to date on methods of setting up for optimum heat generation under low load conditions. I don't think that this particular field is one of Brawn's own fortes. Anybody remembers how helplessly Ferrari acted in early 2005 when the rules were changed for single tyres. Ferrari did not win a single race that year except for the Indy Michelin disaster. Brawn needs to find a clever guy for doing his post rig testing ASAP and get rid of the guy who messed it up for years, whoever that is. What is Pascal Vasselon doing these days? Is he still with the core F1 group at Toyota Cologne?

Are front dampers/inerters in F1 primarily configured to damp suspension travel or tire modes?

They had J-dampers now on both front and rear for many years. They are primarily designed to ride bumps and to keep the wheels on the ground so that the contact patch of the tyres gets maximized. If the tyres do not generate heat you may think the J-damper settings are not really optimized for the job.

Just to make sure we don´t confuse two things here.

A J-damper and a 3rd element damper are not the same, even if mounted in the same position.

Yes it´s true that F1 cars using 3rd element dampers/springs for many years now, mainly to decouple heave and roll mode.
So they still can run "relative" soft springs at each corner for mech. grip and prevent the car from bottoming out under
high aero loads - this is the "job" of the 3rd element, which works most when both wheels go up/down simultanously.

J-dampers are inerters

http://www.f1technical.net/forum/viewtopic.php?t=5865

and came into fashion after the TMD ,pioneered in F1 by Renault, was banned. O.K. thats some years ago as well, but they are not that well understood, and are not an off the shelve product,
which everybody just bolts onto the cars. Some teams still don´t use them.
A inerter is not a "classical" damper in the conventional sense, it´s a quiet neat and trick unit.
DaveW will be able to explain their function much better then I can do.
Inerters are mainly used to control tyre modes, so yes I would think the way they get used is a point of difference in between the teams.

The aim is to transfere more engery into the tyre, so let the tyre do a larger share of the work to dissipate vertical (road) inputs.
It´s a bit like running your car with blocked suspension or a hardtail mountain bike, were all the springing and damping is done in the tyre.

In very simple terms the inerter increases the unsprung mass of the car under certain conditions, so instead of moving up the upright and letting
the spring/damper deal with the road input, the inerter "temporaly" blocks out the suspension, so the tyre gets squashed by the road input.
This squashing generates heat in the tire, helping with tire temp. As far as I know inerters are mainly acceleration sensitive, and provide most resistance
in a quick accelaration input. Large difference between unspung and sprung mass accl.
But as I said DaveW would be the best man to ask.

The trick, is to find the right compromise, as you can´t switch off the inerter when the car is running. And if you generate too much heat in the tires you will
suffer as well. So it seems to be a very fine balance. Now with the parc ferme regulations after qualifying, it is even harder to find the compromise, as otherwise
you would oped for a more agressive setting in qualifying, and then back off for the race, to preserve your tires.

So superior qualifying/ first couple of laps performance may comes at the price of race performance, especially towards the end of a race/stint.
It will be interesting to see, how the race performance / results may shift to other teams when we see some very hot races. (maybe Hungary).

Maybe Mercedes do have some shortcomings in this area, or they do know the answer, but can´t find the means to achieve what they would like to do.
Or need more time to implement their solution. If they have the general weight distribution wrong, this may proves a difficult task, as there is only that much
you can do, with set-up. They have their work cut out, and I´m sure that they will find a solution, the question is, can they do so quick enough.

If the next races are very hot and tire temp generation is not so much of an issue, we could see Ferrari and Mercedes fighting closer to the front, so maybe the
next races are good ones to watch.

Let´s hope that´s the case.

Not sure about that, but I can try.

As you say, inerters do not dissipate energy directly, not intentionally, anyway.

I modelled, as the basis for an explanation, a typical GP2 set-up. I then swapped front & rear tyres (mostly to point out what I think is really wrong with the current F1 tyres) & replaced the front springs with values that are more typical of those used in F1. Here are envelope time histories of front axle contact patch loads (CPL) for the two cases recorded during a simple swept sine input to the tyres, & here is the equivalent for the rear axle. For reference MOD70, plotted in red, is the GP2 set-up, & MOD72, plotted in green, is the same thing, but with tyres swapped & stiff front springs as the only changes. You will see, hopefully, that the changes made peak load variation & the minimum loads worse at both axles. MOD72 shows 2 peaks, the first (left hand one) caused by the sprung mass heave mode & the second (right hand one) caused by the sprung mass pitch mode. The MOD72 responses are worse because the damping ratios of both modes were decreased by the changes. Interestingly, perhaps, rear axle loads are affected more than front axle loads (a typical result). The heat dissipated by the tyres was similar for both cases.

If presented with the MOD72 set-up, I would normally attempt to increase modal damping ratios of both sprung mass modes, which would also improve contact patch load control. This would be achieved by reducing front damper settings and increasing rear. Such changes would be expected to reduce peak CPL variations & increase minimum CPL at both axles. They would also reduce heat dissipated by the front tyres & increase heat dissipated by the rear tyres. Hence the effect of increasing front spring stiffness & then "re-optimizing" damper settings is to reduce heat input to the front tyres & increase heat input to the rear tyres. Not, perhaps, the most intuitive result, but it works that way nearly every time & it does nothing to help a team with "cold front tyre" temperature problems.

I think most F1 teams use an inerter as a front "3rd", which is curious because the best "bang for the buck" in terms of load control is to fit one to the rear axle. I believe the reason is that a rear inerter adds mass high (except RBR) & aft, both considered to be disadvantages in the F1 universe. Anyway, here, & here are front & rear axle CPL envelopes with a "mild" (50kg) inerter fitted to the front axle (plotted in blue). Hopefully, you will be able to see that both heave & pitch modes are controlled better (particularly the pitch mode at the front axle). You may also notice a small bump is the envelopes at around 27 seconds into the run. This is caused by the (mildly de-stabilized) front axle hub mode. The addition of the inerter also increases the heat dissipated by the front tyres relative to the rear - probably a good thing if front tyres are running too cold.

Finally, & just for fun, here & here is what happens if the inerter mass is increased to 200 kg. The effect of the change on hub mode control should be very obvious. Heat dissipated by the front tyres was further increased, which should improve "chemical" grip, but at a cost to "mechanical" grip. Hence the front inerter can be used to "beat heat" into front tyres. However, the performance gained will probably be inconsistent, depending on track temperature, etc.

To summarize, inerters will normally increase control over the sprung mass modes (thus improving CPL &, incidentally, platform control over the 5 to 9 Hz frequency range), but will destabilize the hub modes. Used in moderation, reduced control over the hub modes is not a problem, but the hub modes can become very uncontrolled when the inerter mass becomes too large.

Finally, here is a plot of heat dissipated by the front (shown in red) & rear (in green) tyres for the above cases & a few more (but not re-optimized dampers after the spring change). The legend in the side bar should help to interpret the results. A word of warning, heat dissipation increase caused by the front inerter is over-estimated by my model, because it assumes tyre damping to be viscous, whilst the reality is a mixture of viscous & hysteretic damping.

As you can see, perhaps, life is not so simple when trying to make mechanical set-up decisions without track testing around the aerodynamicists' stake in the ground (stiff front springs are an aero requirement).

Hope the above is not too turgid....

Elaborate on this swapped tires thing. Really grippy front end, crazy loose rear?

+1

Thanks a lot DaveW
Very interesting read, learned something here again.

So may asumption that inerters control mainly the tire mode is/was wrong.
From what you say Dave, it does have some similarities with an increased unsprung mass.

Not really. Just that a mid-engined aero vehicle requires a vertical tyre stiffness split (rear/front) > 1 for good mechanical control. F1 teams, uniquely in my experience, have been struggling with splits of < 1 since 2007 (better this year, but still not right). The "heat rate" comparison between MOD70 & MOD71 illustrates one of the reasons for the required split.

It does have some similarities with an increased unsprung, but responses are not quite the same. Also, a good inerter only weighs around a kilo.

The real disappointing thing is the gradient of the front versus the rear tyres in that



last graph. It basically says you are doomed if you have this kind of problem. Even huge inerter masses will not make a difference to your front tyre heating problem.

Apologies, WB. I didn't explain the last plot clearly (it is a quick & dirty one I use to help to visualize trends during a rig test). The plots represent the rate of heat dissipated by the tyres, red for front & green for rear. Don't worry too much about the numbers, although they do have a basis. The plot shows that adding a 200 kg front inerter is likely to (almost) double heat dissipated by the front tyres. It follows that the inerter will increase rate of heat input to the front tyres significantly, bearing in mind that vertical road inputs are only one source of heat input to the tyres. Logic would suggest it could help to heat the front tyres if they are found to be too conservative. The problem with the extreme 200 kg case is that contact patch load variations are compromised in order to achieve the heat input. Hence the "mechanical" vs "chemical" grip compromise. Even though you might think the case to be extreme, I have seen a device of that configuration attached to an F1 vehicle (& it did help to heat front tyres on track).

For info, & as a "foot to earth", the tyre heat numbers were extracted from calculations that produced this, a plot of work done as a function of frequency by the various vehicle elements that should be dissipating disturbance energy. The legends show peak & average values extracted from the plots. The tyre "Avg" values are reproduced in the summary plot.

LOL Niki. You just confirmed my impression.