Tech Analysis: BMW F1.07

BMW's professional but low key launch in Valencia came in stark contrast to the McLaren event held the preceding evening and it saw the German team unveil their realistic aims for the 2007 season - not a transitional year, but one of maturing.

With the all-new F1.07 they are making a clear shot at the top three teams and the machine features all the benefits provided by the increased resources enjoyed by BMW in their second year as a full manufacturer outfit.

Last year BMW-Sauber produced a radically different car to its predecessors and, aside from Williams, a significantly different car to the rest of the grid by choosing to use a low nose allied to its Zero Keel front end.

Unlike most of the Zero Keel teams, BMW placed the front Bulkhead (the section the nose cone bolts to) much lower and this kept the underside of the nose flat and maintained good geometry for the suspension.

Then, through the rest of the year, the team maximised the availability of BMW funds to grow the aerodynamics dept, running their new wind tunnel and CFD super computer to produce some of the most innovative aero parts of the year.

Even at the start of the 2006 season BMW were developing long-term projects to mature in 2007, including the development of their first complete F1 gearbox as well as new electronic systems. They also made use of their technical partners to create Albert2, their newer and bigger computer for CFD simulations.

Under the team's new aero chief, Willem Toet, CFD has been a huge influence - so much so, in fact, that they are only the second team, after Renault, to announce they have no plans for a second wind tunnel and will instead develop their CFD capabilities.

BMW Sauber's clever new front wing splits the middle section of flap (yellow) to make a three-element wing © Scarborough (Click image to enlarge)

But 2007 will be the year when BMW's increased resources will start to really show dividends, because with this new funding available to him, technical director Willi Rampf has been able to devote a lot more attention to the development of the new car.

Programmes were run to evaluate different cooling solutions and nose configurations, luxuries the Sauber team's limited aerodynamic staff previously had no time to indulge in. This research, initially done in CFD, lead to the shape of the new car.

In layout the car is little different, and Rampf confirmed there has not been any "major dimensional change" to the wheelbase or gearbox and chassis length. The aerodynamic layout, meanwhile, is subtly different in appearance but a major step for the team.

That the increment of the cars aero performance was bigger than Sauber have achieved previously and Rampf confidently said: "It's a noticeable improvement. We improved more than the competition."

In seeking the aerodynamic results Rampf has not chased maximum figures, but has instead followed this years aero catch words of stability in all conditions, an important factor considering the new Bridgestone tyres are likely to see the cars slide and steer more.

These two attitudes hurt a cars aero performance as much as its mechanical grip, thus their development has been to keep as much of the cars downforce available at all the attitudes the car will see on track.

The low nose has been discarded as the team opt for the more conventional Zero Keel design of very high front and dash bulkheads, raising the front suspension upwards in the process, noticeable by the distinct step in the nose in front of the cockpit opening. The higher wishbone location, frees up space for the flow from the front wing and to the fronts of the sidepods.

Ahead of the nose monocoque is a short nose cone. BMW found the new design worked aerodynamically, but the shorter length made for a more involved and demanding design process for the team when it came to the new more stringent crash tests. In shape the nose is noticeably flatter and thinner at its tip, leaving a neatly moulded inlet for cooling the cockpit.

'Bat wing' chimneys neatly integrate the winglets (yellow), as the bargeboards pick up some extra flicks © Scarborough (Click image to enlarge)

This new nose layout also matches to a very clever front wing. While the car was launched and initially tested with a 2006 front wing, the new version was soon tested when eyes were turned away at the car's launch in Valencia.

Made up of two elements and sporting a fairly common shape to its profile, the wing sees the middle section of the flap split in two. This makes the wing effectively a three-element device at its most aggressive section in the middle. The slot this has created allows some flow to pass to the underside of the dipped centre section, reducing separation and allowing the wing to be run at a steeper angle. The wing is matched by Renault-like cascaded endplates, unlike the bolt on versions tried last year.

Again the sidepods were the result of CFD tests with radiators positioned at a flatter angle for better through flow. The shape of the sidepods leading edge has been altered in accordance, as have the preceding bargeboards which now pick up a Ferrari-style extra flick on their trailing edges.

For cooling BMW have developed some very complex chimney panels. The chimneys have the winglets integrally moulded to them, with the inner endplate of the winglet curling around to meet the chimney. The trailing edge of the chimney features a 'bat wing' shape with two curves, one to pass under the winglet and one to rejoin the chimney to the sidepod.

Again the engine cover features a trademark tall spine to provide some resistance to yaw and the roll structure soon saw the return of the viking wings seen from mid season last year.

Structures and mechanical systems on the car were also a source of a lot of development and are a key area due to the new Bridgestone tyres and the uncertainty as to the ideal weight distribution between the front and rear wheels.

"There's always a compromise in stiffness and weight," explained Rampf. "Weight loss is important this year to increase ballast to alter weight distribution. Weight reduction allows us to be more flexible in weight distribution".

A raised front bulkhead moves the front wishbones higher up out of the airflow © Scarborough (Click image to enlarge)

One area that appears to be suffering is the mounting for the lower front wishbones. Many Zero Keel teams mount their lower wishbone flush to the lower edge of the monocoque but BMW, like Ferrari, mount their wishbone offset from the lower edge.

At first it appears the wishbone is set off against the chassis with an inch deep keel or spacer, but Rampf says this is to do with the position of the flexure that pivots the wishbone on the chassis. This is offset from the centre line of the wishbone profile and actually bolts straight into the chassis, leaving the odd looking wishbone ending suddenly under the chassis.

"We have done this for best stiffness of the font suspension," explained Rampf. "The target was to incorporate the lower points of the wishbones directly into the chassis structure."

A result of the limited development allowed to the 2006 engine due to the homologation rules, the engine development is now completed in line with the gearbox at the team's Munich base.

The new gearbox features a seamless shift and a particularly compact rear damper set up, still comprising Sachs rotary dampers. Track testing has already been completed on the new transmission on the old chassis.

With the aerodynamics as advanced as any other team and the engine/gearbox being developed as a complete unit, albeit under a different roof, BMW are now at a similar position as Renault were a few years ago. The cars seems to lack little in terms of design, but the team still have to learn the new tyres, so they will still need to work hard to make up the deficit to the leaders.