Looking back on the Sauber C31

Sauber’s 2012 car, the C31, lost the technical director who oversaw its creation, James Key, just before it was unveiled ahead of the start of the season. In his place the team appointed its existing quartet of technical/operational department chiefs jointly to oversee its development. Many shook their heads and remarked that such a committee approach could never work, yet the Sauber C31 almost tripled the number of Constructors’ Championship points scored by its predecessor, the Sauber C30. Moreover, as a business journalist pointed out, Sauber fought the factory Mercedes team for fifth place in the 2012 Constructors’ Championship “on less than half the budget”. Having to settle eventually for sixth with four podiums to its credit was no disgrace, and was an improvement both over 2011 (seventh, with the best result a fifth-place finish) and 2010 (eighth, with the best result a sixth-place finish). That year, 2010, was the first season since founder Peter Sauber had re-purchased the team from BMW.

With BMW having decided to quit Formula One altogether at the end of the 2009 season, Sauber arranged to revert to the Ferrari engine and transmission package used before the German manufacturer took over. However, the Swiss operation no longer had access to the funding level of the top Formula One teams. It did have excellent wind tunnel and CFD resources established by BMW at its Hinwil, Switzerland factory, but it couldn’t afford to maintain the staff level there when it had been under the ownership of BMW. Sauber did attract Key to Hinwil for a while and his team continued to employ former Michelin tyre engineer Pierre Wache, whose expertise certainly helped the 2011 Sauber to prove very effective on the new Pirelli tyres, a trait that the 2012 car continued. The other key personnel involved in developing the C31 were chief designer Matt Morris (who had joined in mid-2011), head of aerodynamics Willem Toet (who had returned to Hinwil in late 2011 after a spell as managing director of RML in the UK), head of track engineering Gianpaolo Dall’Ara and operations director Axel Kruse.

Against expectations (given its budgetary constraint), the Sauber C31 saw Perez finish runner-up in Malaysia and then again at Monza, while in the meantime Kobayashi had qualified second at Spa Francorchamps. Before that, at Silverstone’s British Grand Prix – round nine of 20 in 2012 – F1 Race Technology had discussed the development of the C31 with Morris and Dall’Ara. First, we asked, given the impressive form of the car, what were the improvements over its predecessor? “We took a strong look at ourselves last year and put down a list of areas where we thought we weren’t strong,” recalled Morris at our Silverstone meeting. “By our own admission, in 2011 we had not been able to use the exhaust effect very well [to activate the diffuser] and that was something we really wanted to target over the winter [despite the new regulations that curtailed the scope for it]. “We also tried to improve our aerodynamic efficiency quite a lot. And we also wanted to give ourselves more scope to make mechanical set-up changes. We felt that, in 2011, trying to get the tyres to operate in their quite tight window was difficult. We didn’t have a mechanical set of tools to do that so we completely redesigned the front and rear suspension. So they were the three big things that we targeted.”

Suspension

Morris continued, “We made some changes which were risky I guess, because with both the front and rear suspension it’s very difficult, once the decision has been made, for us to be able to go back and change it in the season if it doesn’t work. But so far we feel that for all the circuits we’ve been to we’ve had mechanical set-ups that allow us to get the most out of the tyres.”

Where does Sauber stand in terms of the concept of hydraulically linking the front and rear suspension? “I think, to be honest, most people are doing it,” remarked Morris, “and it’s something that’s being discussed in the Formula One Technical Working Group [TWG], as to whether we get rid of it on cost grounds. But the cost of it is very small, and the packaging volume it takes is again quite small. The argument then is that if the FIA takes it off, then we will probably find ourselves developing something that’s even more expensive and more complex.”

We noted that Lotus claims to have used this approach since 2008 (as is recounted elsewhere in this issue). “We started this in 2010 mid-season but we were not regularly running it until this year,” said Dall’Ara (a longer-term Sauber employee than Morris). “Before 2012, sometimes yes, sometimes no. It was not so easy for us to get to this point [of using it regularly].”

Morris added, “This is something that people make quite a big deal of, but to be honest, if we took it off the car tomorrow it’s probably not going to make much of a difference in terms of lap time.” Ultimately though, does it help stabilise the aero platform? “Oh no, we can’t talk about aero,” was Morris’ retort. “Because then it’s an aerodynamic device, so it’s definitely nothing to do with aero. It’s all to do with ride.”

Do you actually link the dampers? “I think I’ve probably already said more than I should have!” Who’s your damper supplier? “We use both Sachs and Penske for various dampers and systems on the car.” Morris then remarked that Sauber doesn’t use the Sachs rotary damper, so we asked about the use of the through-rod concept. “A lot of it comes down to packaging really,” he replied. “Dampers are dampers, and the biggest challenge the suppliers have is when we say we want this damper and it needs to be half the volume and it needs to be half the length. That’s mainly the challenge at the moment.”

Morris confirmed that Sauber uses third – ‘heave’ – springs and dampers, “which I think is pretty common throughout Formula One,” he said. And also inerters? “Yes, we’ve run inerters, and again it’s a setup tool that we choose to use or not.” One key difference from last year’s Sauber was a switch from the well-established pushrod to pullrod rear suspension. Presumably that was influenced by the use of the Ferrari transmission; it seemed that Sauber didn’t really have any option but to follow suit given its supplier’s change of architecture, did it? “[Using the Ferrari transmission] we didn’t have the option to choose between a pullrod and a pushrod,” confirmed Morris. “But within the Ferrari gearbox we still have design flexibility on all the inboard suspension components, the dampers and all the other suspension elements inboard. So although yes, we were forced into a pullrod, it didn’t stop us doing our own internal rear suspension design.”

Morris explained that the 2012 Ferrari gearbox, which is a carbon fibre production with a titanium skeleton to support the shafts, is more tightly packaged than the 2011 production. Is the pullrod approach an advantage? “The advantage comes from aero advantage really; there’s no real suspension advantage,” he said. Have you found an aero advantage? “Basically we found an aero advantage by cleaning up the rear of the car, so having a tighter ‘Coke’ and a lower gearbox case, which essentially going to a pullrod suspension allows you to do.”

Aero efficiency

As Morris pointed out, aero efficiency is something that Sauber targeted for improvement for 2012. “We struggled at some of the lower downforce circuits in 2011, but we are nine races in now and we’ve been pretty competitive at different tracks, like Monaco, Montreal and Valencia. I think we’ve got a pretty well-balanced car at the moment.”

Morris confirmed that all of Sauber’s aero testing, wind tunnel and CFD is done in-house, using (the maximum permitted) 60%-scale wind tunnel models and the powerful computing facility established under BMW ownership. In terms of operating within the Formula One Resource Restriction Agreement, he estimated that the overall effort was split roughly 50-50 between wind tunnel and CFD work He added, “Our CFD to wind tunnel to track correlation is very good. That, from my experience, is the key to making an F1 car fast. You do your CFD, then make some bits and put them on the model, and then you’re going to put them on the racecar, and as soon as there are any doubts in that link, it throws a spanner in the works, and it can be a disaster. So far, touch wood, from what I’ve seen of Sauber [since joining in mid-2011] all of that correlation is very good, and I’m sure it’s one of the keys to how and why we can make a competitive car.” Dall’Ara added, “Since the launch of the C31 we have had a number of development steps, and on top of that we had the special configurations for Monaco and Montreal. Overall, if I relate back to
some of our past season experiences, this year everything worked, which is good for our correlation of the tools that we have at home, since testing on track is not allowed any more.”

Exploiting exhaust

Sauber was one of the first teams to exploit the ‘Coanda effect’ following the repositioning of the exhaust pipes, further back and higher up, enforced by the 2012 regulations.

On paper it seemed that there was no longer any possibility of exhaust gas blowing along the sides of the diffuser, to form a virtual seal against the ingress of high-pressure air, to the benefit of diffuser operation. However, although the pipes now had to exit high with a slight upward tilt, the provision of a channel on each side to encourage their discharge to flow down to the floor where it could be put to useful effect was feasible. This was due partly to the Coanda effect – the tendency for a fluid flow to follow an adjacent surface – and partly to the general downwash of air caused by an appropriate sidepod form. Sauber incorporated such channels into the rear bodywork of the C31, and enjoyed an exhaust-activated diffuser. There was a risk though that this ploy, flying in the face of the apparent spirit of the new regulations, would be deemed illegal. “Yes, we took a big risk with how the FIA would interpret it,” agreed Morris.

“There were two risks for us. The first was that, when we tried to get the exhaust effect working last year, we failed miserably. So we spent a lot of money on that and it bought no performance gain. In fact, in the last few races of 2011 we decided to throw it all into the bin and just put ‘normal development’ on the car. The second risk was that, compared to other teams, we have to make our decisions quite early, and we weren’t sure how the FIA was going to take this design, but we kept the FIA informed of what we were doing – we thought that was the best approach – so if they had concerns they could have told us quite early on.

“As it turned out, both those things worked quite well. I think we’ve been pretty successful with the C31’s exhaust [discharge] layout. We were ahead of a few teams at the beginning of the year, and it’s nice when some of the top teams then come sniffing around your car and have a look at what you’re doing, and then turn up with similar bits. I think it’s something that originally we definitely made a better job of than most other people, and I think it’s something we now understand a lot better, which has allowed us to develop the car through the season as well.”

In terms of the team taking such a risk on its Coanda exhaust strategy, Morris had some interesting comments. “Coming to Sauber as an Englishman who had worked only at English teams, in the first few months of being at Hinwil I was a bit frustrated at the conservatism I found. And for sure, some people still at the team are still conservative, but now we’ve had a year where we’ve pushed the boundaries a little. Hopefully it’ll be a strategy that we can use again in the future and get even more people behind it.

"Certainly, if you’re a conservative Sauber team, you’re going to be midfield, towards the back, consistently, every year. If you really want to make a step forward, you have got to take some risks"