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Midway through the 2006 season Renault suffered a setback when the FIA outlawed mass damper technology. A number of teams, including Renault and Ferrari were using it but at that stage Renault had made more effective use of it than its rivals.

WHAT IS A MASS DAMPER?

A suspension damper acts in conjunction with a springing system to influence the movement of an unsprung mass – the respective wheel and tyre assembly and its attendant linkages. In turn the combined motion of the four unsprung masses influences the movement of the sprung mass. In fact in the case of a Formula One car, we should say ‘semi-sprung’ rather than ‘unsprung’ for each tyre acts as a spring in its own right.

The Formula One car is very stiffly sprung since control of the aerodynamic platform formed by the sprung mass is considerably more important than the enhanced mechanical grip that comes from a more compliant semi-sprung mass. It is this compromise that explains why the Formula One tyre is specifically designed to act as a spring. However, the implicit lack of compliance, which the carefully designed ‘give’ of the tyre sidewalls can only partially offset, leads to surface irregularities causing fluctuations in the load at each contact patch.

The aero platform might be kept reasonably stable but the download it produces has to act through the four tyre contact patches and fluctuating contact patch loading implies a fluctuating level of grip. This will make the car harder to drive and slightly slower that it would otherwise be. The mass damper is a device designed to even out those fluctuations.

The mass damper reacts to vertical displacement of the sprung mass but the devices used in Formula One this season were not powerful enough to counter longitudinal shifts in weight caused by acceleration or deceleration. Rather, the technology was intended to counter the effect of surface irregularities while the tyres were laterally loaded.

As used by Renault and others the mass damper consisted of a sealed cylinder located upright in the front of the chassis at a mid point between the two semi-sprung masses in conjunction with which it worked. In fact, this season Renault used a second such device at the rear, having pioneered the concept with a single unit at the front of its 2005 contender. The rear unit was located at the front of the gearbox.

Inside the cylinder was a disc sandwiched between two coil springs and the unit was filled with damper oil. The disc, which in the case of the Renault weighed in the region of 10 kg was free to move up and down the cylinder except as constrained by the low rate springs and the fluid. The device was ‘tuned’ by either changing the clearance between the disc and the cylinder bore or by two-way adjustable valving embedded within the disc itself.

The disc reciprocated in its cylinder in response to movement of the cylinder, which was rigidly attached to the sprung mass. Irregularities causing fluctuating loading at a contact patch cause in turn vertical displacement of the semi sprung and the sprung masses. The moving disc within the mass damper reacted to that movement of the aerodynamic platform in a manner determined by its weight and by the action of the springs sandwiching it.

In turn the movement of the disc, reacted through the springs and oil, put a force into the chassis to neutralise the effect of the vertical movement caused by surface irregularities, counteracting fluctuation of the loading on the tyre contact patch.

In the case of the 2006 Renault Formula One car, with a mass damper at each end the total mass damper weight was in the region of 20 kg. The car had to weigh 605 kg and more than 40 kg of ballast was required to reach that minimum, consequently there was not a weight penalty in building two mass dampers into the car. Potentially there was a negative impact on centre of gravity height and on flexibility of weight distribution but clearly these were more than countered by the effectiveness of the mass damper system.

For Renault the use of mass dampers added stability to the car and, particularly at the front where the suspension is stiffer than the rear, potentially permitted the use of even stiffer suspension spring and damper settings, to the benefit of aero performance. However, it was not straightforward to make even a marginal performance gain from the technology.

Renault’s exploitation of the concept followed a number of years of experimentation with Michelin’s ‘Optimised Contact Patch’ (OCP) suspension system, which was eventually deemed illegal by the FIA. Resources were then put by the team into mass damper technology at a time when there was no automatic gain to be had – this brave pioneering work eventually gave Renault a march on its rivals. When those rivals realised what they were missing some rushed to produce their own systems but others rushed to get Renault’s advantage outlawed, just as the OCP system had been.

THE MASS DAMPER AFFAIR

The mass damper affair blew up in the week preceding the German Grand Prix, when, on July 26 the FIA wrote to the teams to ‘clarify’ its position on the use of the device. In this letter it said that, while its view in the past had been that they do not contravene the technical regulations, “recent evidence and an escalation in development by some teams has made it clear to us that the principle purpose of these devices is to improve the aerodynamic performance of the car”.

The FIA noted that the regulations insist that any part of the car that influences its aerodynamic performance must remain immobile in relation to the sprung mass. Mass dampers directly influence the loading of the tyre contact patch. By potentially permitting the use of stiffer suspension settings they can be seen to indirectly influence the aerodynamic performance of the car.

The FIA stewards at the German Grand Prix accepted Renault’s argument that the purpose of the mass damper was to influence the loading of the contact patch, consequently it was not an aerodynamic device and should still be considered legal. However, the FIA appealed its own stewards and the matter went to an FIA Court of Appeal on August 22. In the meantime, Renault ran the German and Hungarian Grands Prix without the use of mass dampers to avoid the potential loss of points. In the event, the court declared mass dampers illegal.

Why did the FIA stop the use of mass dampers?

There was a fear that the devices would become heavier and thus create a greater safety hazard. In fact, it seems that Ferrari put the wind up the FIA for it had not found mass dampers as effective as Renault clearly had. The mass damper affair harmed Renault, which had used the technology since 2004 and had designed its 2006 car around it, more than it did Ferrari.

Nevertheless, although Renault lost performance running for the first time without mass dampers in Germany, their loss was not a “night and day” performance issue, according to Bob Bell. This was shown by the subsequent competitiveness of the car when running without them.

The Formula One flexi wing has sufficient structural integrity to hold its static form under the download generated when at maximum cornering speed. But the increased loading that comes with higher speed on the straight deflects it – or part of it - so that it sheds downforce and with that drag.

The rear wing has two elements and some of the downforce (and with it drag) that it creates can be shed by opening or closing the slot gap in between the two elements. For example, it can be arranged that under a certain load the tip of the flap moves closer to the main element, reducing the gap. The gain can be worth 5 mph extra top speed.

Clearly this aero-elastic approach is easier where there are low speed corners and long, thus fast straights than where the speed differential is less. But in 2006 it appeared that certain Formula One teams could take advantage even on circuits with high speed corners.

Sophisticated computer-based modelling was at the heart of this, that and advanced manufacturing techniques. All carbonfibrebased bodywork elements have some degree of flexibility, however miniscule. The key is to exploit the phenomenon of aero elasticity so as to find a gain without transgressing prescribed FIA checks. It helps that advanced composite material is highly tuneable in its characteristics throughout a part and that those characteristics can be specified through a combination of Finite Element Analysis (FEA) and Computational Fluid Dynamics (CFD) work.

At the same time the FIA checks are simple two dimensional static tests whereas the reality is of complex three dimensional dynamic behaviour. For example the FIA has a deflection test that assesses the flexibility of the uppermost rear wing element at three specified points along its span. We saw in 2006 that the prescribed static test doesn’t mean that in the dynamic state wing elements cannot be designed that flex in a manner that beneficially alters the slot gap at a crucial speed.

Ferrari started the 2006 season in Bahrain with a rear wing that passed the specified FIA test but which rival teams considered in the light of what they saw on track to be unacceptably elastic. There was further controversy at the next race, in Malaysia, when on-board camera footage appeared to show a Ferrari front wing element deflecting.

Eight rival teams threatened a formal protest on the basis of the ruling that states that any part of the car that influences its aerodynamic performance ‘…must be rigidly secured to the entirely sprung part of the car (rigidly secured means not having any degree of freedom)’.

In response the FIA closely inspected the Ferrari and the cars of two other teams, McLaren and BMW-Sauber. All were deemed legal but the FIA asked for bodywork modifications prior to the next race in Melbourne so as to put those cars within the spirit as well as the letter of the regulations.

While modifications were duly made, that was not the end of the affair. Amid on-going concern, for the Canadian Grand Prix the FIA made mandatory a slot gap control bracket on the centreline of the car, holding the flap in respect to the main element of the rear wing.

That still wasn’t the end of the affair. In Canada and the USA, the BMW-Sauber continued to come in for criticism from rivals. The FIA asked it to make changes prior to the French Grand Prix and then it asked the team to make further modifications for the German Grand Prix. Both Midland cars were disqualified from the results of that race for excessive rear wing flexibility, which was blamed on a manufacturing fault. Or was it a case that it wasn’t just BMW-Sauber still playing the game!

Moreover flexible bodywork doesn’t have to only revolve around the rear wing slot gap. In the past certain teams have had a wing support pillar deflect sufficiently to beneficially alter the angle of attack of the entire rear wing. Current stiffness tests rule out that approach but there is apparently still scope to do something in the area of the rear wing endplates…

A flexing rear wing impacts upon the performance of the diffuser since the two strongly interact. The operation of the wing encourages air to flow through the diffuser: if the wing stalls then the diffuser will likely stall, too.

Diffusers do deflect under load while bargeboards sink under load. However, the amount that they can be designed so to do is limited by current FIA regulations. But the aerodynamicists will continue to exploit aero elasticity wherever they can. It has even been suggested that air could be pumped into a wing element so as to balloon it and thereby alter its external form!

In the summer the BMW Sauber F1 team surprised with a pair of parallel vertical fins standing proud on the scuttle of the 06/P86, the leading edge of each adjacent to the respective forward upper wishbone mount. Exploiting an area free under the technical regulations, these radical fins were devised by Sauber’s in house aero team headed by Willem Toet.

When the car was in yaw, logically like any such vertical fin they created a lateral force but this was not their design purpose and was an unwanted side effect. Clearly they channelled air passing over the fuselage and it appears they assisted most whenever the car had some front wheel steer angle to upset the flow regime back over the car. They had the effect of cleaning up that dirty air, to better channel the flow to the rear wing.

No such device acts in isolation and these fins were used in conjunction with tabs sprouting from the engine cover. In straight line running the fins might well have acted as lifting devices. Current Formula One cars have a number of components aft of the front wing that intentionally create lift rather than downforce. This is simply to reverse the upwash created by the front wing; generating positive lift creates a downwash and pushing the air back down like that helps the feed to the rear wing. Improved rear wing performance more than compensates overall for the unwanted lift.

Reportedly the fins were found of particular benefit when the car was running in traffic, clearly helping reduce the adverse effect of dirty air. Surprising some, the drivers did not complain of a significant loss of visibility.

The fins were first seen in testing at Jerez, Spain July 4-7 2006. The FIA had been informed prior to their use and its scrutineers deemed them fit to race in the French Grand Prix, July 14-16. However, after the race the FIA noted: “we have become concerned that these devices may impair the forward and/or lateral vision of the driver.”

The FIA then added: “unless any team concerned can clearly demonstrate to the satisfaction of the technical delegate and the stewards that their driver’s vision is not impaired in any way by such devices, no bodywork higher than the top of the front roll structure will be permitted forward of it.”

Clearly BMW-Sauber could not satisfy the FIA for the devices disappeared thereafter.

Prior to 1994 Indy Cars used wheel covers on Superspeedways, for on such tracks there was no issue of brake cooling. In 1993 Penske reported that such covers could reduce drag by 2.5% for a given level of downforce. They were subsequently banned.

In general, racecar brakes and wheel bearings are cooled by scoops on the inside of the wheel and the hot air exits through the spokes. The spill from the wheels creates drag and at the same time the pumping action of the wheels can pull air away from the underbody area, reducing downforce. But the whole airflow regime around each wheel is extremely complex.

At the Turkish Grand Prix, round 14, Ferrari, Toyota and Toro Rosso all appeared with carbonfibre rear wheel shrouds, having just a small hole in the centre for the escape of hot air (also providing access to the wheel nut). This approach cleverly limited the wheel through flow to that sufficient to provide adequate brake and bearing cooling and no more. The rest of the air that would otherwise have escaped through the spokes was now travelling inside the wheel, presumably in such a way that it beneficially interacted with the rear airflow regime.

On top of this, the shroud itself reduced drag but overall it was much more than a revival of the Indy Car wheel cover. There were two possible objections to it. One, it constituted a moveable aerodynamic device and, two, the wheel was no longer of a single material, which is a stipulation of the regulations. The FIA did not find either objection to be sustainable.