The Insider: Interview with Pascal Vasselon

Toyota did not have a great year in 2007; the car struggled from its first tests and never really got off the back foot through the season, despite a strong finish to 2006.

As the leader of the team's chassis department, Frenchman Pascal Vasselon has overseen the cars' design and development through the season, and is uniquely positioned to comment on the problems that were faced by the team.

Vasselon studied aerodynamics at the Sup D'Aero before moving to Renault's road car division, and later, Michelin's F1 operation. He has now been at Toyota for over two full seasons, taking the team forward from its post-Gascoyne era.

His knowledge of chassis dynamics is perhaps unmatched in F1, and the insight he can provide on tyres, makes him one of the most enjoyable technical directors to talk to. Autosport.com was able to talk to Vasselon after the end of the season to gain some understanding into the design and development of the TF107 car through a difficult year for the team.

Design

Toyota attracted a lot of criticism about the apparently dated design of the TF107 car; the high nose and conservative sidepods suggesting that the team were lagging behind the rest of the field. However, Vasselon is content that the design philosophy was correct.

There has been no major mistake, no major issue with this concept," he said. He added that the car's lineage was the reason for its appearance:

"TF107 was in fact an evolution of the aero concept of the TF106, then repackaging to move the engine forward, the gearbox forward and a more aggressive driveshaft angle."

Adding the unusual front end was also an evolution of the 2006 car, "continuing the direction of the TF106, to increase the height of the monocoque at the front and refine what we call the Anhedral front suspension".

Certainly, the team's recent history of mid-season B-spec cars has put Toyota out of sync with the rest of the field, which adopts a new aero concept and chassis at the start of each season.

Toyota has tended to bring an aero concept out first, then produce chassis upgrades around every six months. The lack of rule changes for 2008 suggests Toyota might now switch back to a conventional 'new car' philosophy.

At the end of 2005, Toyota announced that they were moving from Michelin to Bridgestone for the 2006 season. Thus, they were one of the few teams not to have to switch suppliers following the sport's move to a single tyre supplier a year later. I asked Vasselon if this was still a problem for the team.

"It was at the same time, easy and difficult," he said. "It was quite easy to begin with really, because with these sorts of tyres, you just put them on the car and they work".

He added that their earlier switch to Bridgestone was indeed a benefit for this year, as the winter 2005 testing was with the older long-life tyres that this years' tyres were based on.

"We had the first flavour of them at the end of 2005," he said. "The first running we did with Bridgestone was with very similar constructions and compounds, before they developed to the very different 2006 tyre generation. So we have experience".

But still there was work to do.

"What was difficult was to extract the maximum from these tyres," he said. "With this tyre construction comes a major balance change for tyres. They induce a lot of oversteer because of the weakness of the rear construction, so you have to develop the car around that. To make it simple, you have to build in understeer in the car".

This is particularly useful in understanding the problems that both teams and drivers experienced in 2007. The car's balance had changed due to the tyres; this meant the teams had to reduce the mechanical grip at the front of the car to make the rear tyres last.

"This is fine for some drivers," Vasselon said. "It suits perfectly the style of some drivers, and I would say most of them did not have major issues. [But] some of the drivers have struggled to adapt to these tyres in terms of car balance - Ralf [Schumacher] is not the only one; Kimi [Raikkonen] has had problems, as has Fernando [Alonso]"

Again, Vasselon's previous experience in supporting Michelin's tyre effort in F1 gives him broader understanding of the issues faced by the drivers.

"I would say what these drivers have in common is they like to drive the car on the nose," he said. "They like to have a very neutral car, with very strong front axle. With the 2007 Bridgestone this was very difficult to achieve without major instability problems or consistency problems".

What made the tyres difficult to handle for some was the stiffness of the front tyre. Vasselon put it into simple terms.

"It's the cornering stiffness, the amount of force the tyre generates laterally for a given slip angle," he said. "The cornering stiffness on the front tyre was especially powerful. It's a kind of paradox, because you would expect from that to find the car would be on the nose"

As the rear tyres were weaker, the teams couldn't find the balance they wanted. They simply couldn't make the most of the front tyre.

"The problem is, if you don't do anything, the car is on the nose, but to the point where it's not workable," Vasselon explained. "It's to the point that you have too much braking instability and turn in instability".

To improve the car through the year, Toyota had two development paths to follow - chassis and aerodynamics. In managing the tyre issue, the chassis was a greater focus, as Vasselon explained""

"We have tried more and more to put understeer in the car, we have developed a lot of mechanical understeer in the car, to control the tyres".

As well as this chassis tuning to overcome tyre issues came the perpetual drive to improve aero efficiency. "You just have to do it, step by step, to increase the aero efficiency of the car," said Vasselon.

During the year, the Toyota was updated in three distinct aero packages. "These aero packages are constituted of parts which have strong interaction with each other, so you cannot really change them one by one, front wing, floor, diffuser and engine cover," he said.

Arriving in Barcelona, Budapest and Fuji, the aero package updates were important, but Vasselon also pointed out that smaller upgrades were more frequent and as important.

"In between [the major updates] we had [new developments] at almost every single race," he said. "We had upgrades on parts like winglets and brake ducts - parts which are never working on their own, but with less interaction with the flow structure of the car".

Both of these issues came together with the problem of the tyres' shape and deformation characteristics affecting the aerodynamics. While some teams cited this as their biggest issue of the year, Vasselon felt that it was not the case for Toyota.

"It has not been particular problem, and it should not be," he said. "Tyres are highly deformable, so when you have a tyre on the car, whether it's a Michelin or Bridgestone, you expect it to have large deformation in cornering and so on".

In Vasselon's mind, the change in tyre supplier should not have been the reason for any lack of performance.

"Normally, your car should not be too sensitive to tyre profile, simply because you have more difference between a deformed Michelin and static Michelin, than between the Bridgestone and Michelin," he said.

"The only sensible thing you can do in terms of aero development is to make the flow structure insensitive to tyre deformation. Then, as soon as you achieve that, you should be able to change tyre profile quite easily."

This suggests that the tyre problems experienced by other teams was the result of a greater problem.

"If your aero package is sensitive to tyre shape to the point that changing from one manufacturer to another creates an aero problem, then you have a major aero problem," Vasselon agreed.

As with all teams, Toyota have access to Bridgestone's pneumatic wind tunnel tyre to replicate some of the tyre's deformation during the race - which brings us to Toyota's second wind tunnel. I asked Vasselon whether the team had focussed on the second tunnel rather than a major CFD programme?

"We have done both," he answered. "It's very difficult to disassociate the CFD and wind tunnel.

"At the moment it's quite clear that CFD alone is not able to do the job. CFD is good for a qualitative approach; it gives keys to understand what happens. As soon as you have to quantify - and eventually you have quantify things - you have to go into a wind tunnel".

The lower profile of Toyota's CFD program compared compared with some other teams suggests that their resources are well capable of providing both tools for development, which is an obvious benefit.

"For me, the question for F1 teams at the moment is not to chose between the CFD approach and wind tunnel approach," Vasselon said. "You need both to feed the other. That's what we are doing, we now have two wind tunnels and we have our CFD approach".

In addition to the tyre development, a new program for the team in 2007 was the partnership with Williams for gearbox development.

As the teams now share the same engine, the joint development on the seamless gear cluster was an obvious step. Williams had raced their system throughout 2006, and the new set-up was an all-new system, which meant that they had created a second-generation seamless gearbox just as most teams was just developing their first.

Being almost self-sufficient, Toyota are not used to working in partnership on such major projects. But was this a problem for the team? "Actually the joint development program worked pretty well," Vasselon said.

Indeed, Vasselon was proud of the performance of Toyota's gearbox during the season.

"After the conclusion of the season, we have absolutely no retirements related to the gearbox," he said. "It worked very well, [although] I think once or twice we had to finish the race in the so-called 'back shift' mode, when the normal mode was not working any more.

"We started the operation based on the Williams cluster, then all the development of the cluster has been done together. But the joint program has allowed us both to develop the software, which was the most important thing".

The operation of the seamless system is still a secret, and Vasselon revealed little information about it.

"The principal of the seamless shift is, you engage two gears at the same time," he said. "The fact you engage the second gear allows you retract the first one. The timing is critical, and the change of torque path allows you to remove the first gear.

"The target is to have continuous torque transfer, which is where you gain the lap time - the lap time gain is around 0.3s. Then it can even be more after a while, as when you have seamless shift you can shift on corners, or you have a different gear ratio optimisation. It's quite powerful".

Development

During the year we have followed many of the team's developments. The new engine cover introduced at Silverstone was one of the first major visual changes. Despite the obvious appearance of the fin along the spine of the engine cover, Vasselon said that it was not a big gain for the car.

"It was not a major thing," he said. "We put it on the car simply because it cannot hurt".

So if the fin wasn't working to improve the car's downforce, what was its value?

"If you add surface area to the rear, you gain stability from lateral wind," Vasselon explained. "Something which is very well known for people at Le Mans, for example. At Le Mans you always see large surfaces at the rear of the car; it just gains you stability from lateral wind".

Later in the season, the team appeared with a new front end comprising a revised wing, revised endplates, a drooped nose cone and revised bargeboards. This necessitated a crash test, as well as the manufacture of the all the new parts, I asked if this was a big project to tackle late in the season?

"I would say yes and no," Vasselon replied. "First, it's not easy, but we have now a crash test approach that is predictive enough to develop without using too many resources.

"The nose cone went on the car earlier than expected. It was expected to be part of the Fuji package, but went on the car in Turkey. The target of this nose was mainly to reduce the yaw and steer sensitivity of the front wing. It came together with some efficiency improvements".

Another big development was the adoption of the Ferrari-like front wheel fairings. Vasselon's take on their use differs from the popular perception of the devices acting as brake cooling and drag reduction aids. In Toyota-speak, these parts are termed 'rim blankings'.

"Honestly, the effect of the front wheel blanking is not something you can capture very simply," Vasselon said. "We have now some experience with it. Very clearly, it can have totally different effects according to the rest of the flow structure over the rest of the car.

"It's a powerful item and you can use it in different ways. It's not only a drag reduction item, and really can change a lot of things in terms of front wheel wake".

Surprisingly, Vasselon feels that the blankings do not have a brake cooling effect at all.

"It affects the brake cooling," he said. "You need to step up the brake cooling. In our case it has not been a problem because we are not really marginal on brake cooling, and adding some brake cooling was not really detrimental in terms of aero efficiency".

As well as the actual fairing and wheel nut combination, the front upright and hub needed to be revised. This was another big job for the team late in the season.

"It requires a very interesting design in terms of the extension of the front hub, with the rotation of the wheel and not the rotation of the rim blanking," Vasselon explained.

However, unlike Ferrari, the parts were first raced without problems for the pit crew.

"We have introduced it without major issue," he said. "I would say without the mechanics getting hurt, or any problems at the pit stops.

"Actually we saw that at the last race - we lost five or six seconds with Ralf at the first pit stops, [and] we thought on the spot that it was because of a problem with front the rim blanking.

"In fact, it was not - he had a contact at the start with the Toro Rosso which damaged the nut, so in fact the delay was not directly related to the rim blanking. It was something that would have been there without this feature".

Lastly, the team ran two different rear diffusers for the last quarter of the year. The appearance of the new floor and subsequent reappearance of the old floor at different races led to suggestions that the new floor wasn't a success. Vasselon refutes this.

"I wouldn't say that," he argued. "In the last races we were playing with the two floors according to the track layout. We went with one or other.

"In Fuji trim, we have been using the Fuji floor and it was the best. Earlier in Spa we were comparing the two and chose the old floor - it has to do with the density of high speed corners relative to low speed corners. The two floors are different at different circuits".

In visually comparing the two floors, I had noted that the only difference was the shape of the central tunnel. Vasselon backed this observation up: "The difference between the two floors, which was also giving the difference in character, was the level of expansion of the central part."

Reliability

Throughout the year, Toyota remained one of the most reliable teams. With no engine failures to report, the only major problems were the failures to the suspension. This problem appeared in Canada, where the suspension of Trulli's cars collapsed. This was traced to a failure in the upright, and I asked Vasselon what the problem was.

"We were running on that day a very stiff set up, so the combination of the driving line and a stiff set up [caused the problem]," Vasselon said. "It's obviously a weakness of the upright - you cannot brake an upright without coming to the conclusion that it was too weak"

Fixing the problem was quite simple: "When we understood where it was coming from, we could make a few steps on the car's set-up, and I asked Jarno to change his driving line and avoid this part of the kerbs," he said. "Fortunately, it is something we have reviewed since then".

Indeed, the as original upright was made in MMC; this material was changed to titanium for some of the races later in the year. Keen to avoid a recurrence of the same problem, the team have reviewed the parts for 2008.

"We have just started some load cases in our suspension definitions," Vasselon said. "We define our suspension on the load cases which are representative of the most serious conditions for the season, so we have added the load case for Jarno from Montreal".

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