Tech analysis: BMW-Sauber F1.06

As two experienced Formula One companies merge, BMW's engine and drivetrain skills are matched to Sauber's chassis and aero knowledge. The resulting car is strangely new and old at the same time.

There are clear design clues from Sauber's C24, but also elements similar to recent Williams cars. These have been added to a car that is totally new and adopts some wholly new concepts in layout.

The design for the F1.06 started back in July. By this time, the problems affecting the C24 were understood, and the remedial aero upgrade package was already released at the start of the European season.

Although the C24 did not have a great season, Sauber were happy as there were no major problems that needed to be addressed when considering the new 2006 car. In fact, the 2005 car's primary limitation was the rear suspension's ability to make the most of the Michelin tyres - something that required a new gearbox case.

By this stage, Sauber knew that a BMW V8 would be in place for 2006. It is BMW's intention in the future to supply the complete engine, gearbox and electronic systems.

However, from a standing start, the creation of an all-new gearbox was out of the question and the Sauber-developed (and not a Ferrari design) unit from the C24 has formed the basis of the new gearbox. This left BMW to focus on the engine and electronics, and commence a longer-term gearbox project.

To meet the new rules, BMW-Sauber had to alter the C24's layout to make up for the ten centimetre shorter engine and also alter the suspension to suit the Michelins and mid-race tyre changes.

BMW-Sauber took the logical step to extend the gearbox casing, to make up for the shorter engine; along with the 10cm extension, they altered the suspension mounting points.

The rear suspension, compared to last year, is completely different - mainly to optimise the performance of the Michelin tyres. These needed a different kinematic velocity - something Sauber weren't able to do in time last year but have prepared in time for 2006.

As with all teams, the 2006 cars allow the designers a chance to re-optimise the car's design to reflect the raised front wing and lower diffuser dictated in the 2005 regulations. The case of the F1.06 was no exception, and the whole chassis has been moved lower down.

The main purpose is to get more free airstream to the floor and this also leads to different suspension pick up points. As a result, the new car would be largely designed around Rampf's idea for a flatter horizontal space under the nose.

In order to do this, the technical regulations have several dimensions that need to be adhered to. First is the minimum size of the front and dash bulkheads and the distance they are apart. It is these two rectangles that enforce the uniform square chassis of current F1 cars. However, the rules do not dictate how high these bulkheads must sit; only the cockpit opening sits at a specified height.

In recent years, teams have raised the two bulkheads as high as possible, even higher than the cockpit's opening in some cases. This frees up the most space under the nose but also makes the underside of the chassis slope downwards.

What Sauber have done is lower the front bulkhead to leave the underside of the chassis almost horizontal, with the top of the chassis sloping upwards towards the cockpit. A by-product of this approach is the wishbone's cam mount with a keel to the chassis, without the extreme angles seen on the McLaren/Toyota keel-less designs.

One compromise in this layout for the front suspension is that the pushrod needs to operate on a less effective angle. Furthermore, the design of the rocker that operates the torsion bars and dampers needs to be revised to maintain the correct compliance levels.

Amid all the talk of the BMW takeover, the new car launch and the new drivers' line-up, the fact that BMW have produced an all-new engine to meet the new rules remained almost forgotten.

Unlike their rivals, BMW chose not to go to an interim engine by modifying a V10, but instead went straight to a purpose built V8 designed around the rules. This unit first ran on the dyno in May last year, and it was installed in a Williams chassis for a run in July.

This gave Williams and BMW the chance to evaluate the power characteristics and vibration issues of the V8. When the V8 first ran on the dyno in Munich, BMW motorsport director Mario Theissen noted the vibrations were terrible. "I can tell you when we first had the engine on the dyno, we asked [Sauber's technical director] Willi [Rampf] to come over and have a look because it damaged the dyno bearings as it was jumping up and down on the dyno!"

Since these initial tests, the vibration issue has not been a problem for Rampf on the chassis side. "There were a lot of complaints about vibration from the engine people," he said.

"We had the interim car, just modified for the engine mounts and accommodate the oil tanks, and we had no problems on the chassis itself. It's not so critical as it is, say, on a dyno. We had no vibration related failures, we have modified some components to make them stronger or placed them in a different location. On the car, overall, it seems the carbon structures are not very sensitive to these vibrations."

As with all teams, BMW-Sauber are working hard on reliability, as yet the engine has not achieved a full two-race mileage on track. But Theissen is not worried by reliability for the first race; instead, he claims the rule changes will lead to a wider spread of power between the engines on the grid. Currently the engine manufacturers agree there is a variation of only a few percent between all of the engines.

From images of the engine that were provided by BMW, it is clear the unit retains a conventional shape bock and mounting points. Additionally, the engine retains BMW's preferred large airbox - something that has a visual impact on the outside of the car, as the bodywork bulges to wrap around the airbox.

F1.06 in detail

Aside from the revised BMW motorsport colour scheme, the nose and front end dominate the car's look. The front wing is an all-new design, with Sauber having run flatter designs last year with the slat-like chin wing assisting their effectiveness.

Last year Sauber did quite a lot of development work on the front wing, but according to Rampf, "we didn't have a real breakthrough."

"This year we have again done a lot of work on the front end and combined it with the rear end, and we found a good compromise on how the front interacts with the rear end."

The new wing is a more typical curved design with extra flick ups at the outer ends. Its two-element design is matched to conventional endplates, which also feature the small cascade flaps first adopted by Renault.

The nose cone mounting the wing has cranked underside to convert the higher nose tip position into the lower bulkhead. With the wing plus its flaps and the curved nose cone, the whole assembly has a coincidental appearance to the Williams 2005 design.

The front end of the chassis is clean with no keel or other disturbances, only the unusually wide mirror mounts upset the lines. While the forward pair of bargeboards are mounted to the lower edge of the chassis - and at first could be mistaken for McLaren-like keels - the quite long vanes lead back to large mid placed bargeboards similar in formant to Sauber's C24 boards.

These link to the sidepods without the axe heads adopted by most other teams, but the car is possibly at an early stage of aero development, so these might be seen on the car before Bahrain.

If the sloped chassis top is new, the sculpted sidepod inlets are clear progression from Sauber's 2005 car.

Placing the inlet ever high up and in a more curved plane, the deep undercuts lead air passing under the chassis around the car and catch it beneath large flat flip-ups. The flanks of the sidepods are extremely rounded; the F1.06 - unlike the old car - uses flat radiators mounted at a compound angle, rather than the folded set-up previously used.

Cooling was at first provided solely by large rows of louvers, but later in testing chimneys less angled and curved than the C24's reappeared ahead of the small sidepod winglets. Buried into the sidepods were the exhaust outlets, and like last year, these are placed far forward, by putting a U-bend in the secondary exhaust pipes.

These exhausts blow over the engine cover toward the rear wing. Surprisingly, the engine cover does not have a notch cut out at the tail end; instead, the fin-like spine of the cover starts to part way down the snorkel and ends vertically.

This exhaust and engine cover work is aimed to improve flow to the carefully sculpted rear impact structure. This has to undergo a more severe test this year, and BMW-Sauber have tackled this in a very different way.

From the tail of the gearbox the structure remains largely at the same height, pushing the middle of the rear diffuser tunnel, with only a moulding holding the light in place, extending up from the main design.

An advantage of this route is that the heavy impact structure remains low and straight, which is better for managing the impact and should weigh less. However, the structure takes up a lot of space in the central diffuser tunnel, which is the critical area of the underfloor in creating downforce. Rampf cites rear wing performance - and the ability to beneficially mount the mini wing - as the driving factor in the design.

Beneath the impact structure, a new layout of diffuser is adopted. The central tunnel remains quite flat and then aggressively steepens under the lower beam wing. This almost sheer exit to diffuser is a visual demonstration of the steep upwash that the FIA is trying to manage with the CDG wing in 2008.

The rear suspension design was, as mentioned, not done for aerodynamic reasons, but rather the new geometry aims to get more out of the Michelin tyres and thus fairly modest wishbones are used.

Above the gearbox, the Sachs rotary dampers are still in use, even though Toyota, for one, have preferred to move away from such a design.

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- The Autosport.com Team

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