Every year High Power Media, who publish ‘Race Engine Technology’ (RET) Magazine, produce a number of magazine format Race Technology Reports. Covering F1, Moto-GP, Nascar, Drag racing and 24-hour racing.
Just out is the current F1 Race Technology issue, covering Technical subjects from 2011 and 2012.
McLaren went into 2011 with an aggressive design strategy, this was a response to the poor initial form in 2010 and resulted in the dramatic “U” sidepods and a mysterious exhaust system.
It was this exhaust system that stole most of the column inches in the F1 press and the fan forums during pre season testing. One particular column fed the interest around the exhaust and christened it the “Octopus”. The article suggested the exhaust was ducted to several exits and used high temperature Glass Ceramic Carbonfibre (GCC). It went on to explain the unreliability of the exhaust solution was due to the heat making it fail.
It was true McLaren’s first tests, even from the first private shakedown runs before the public testing had started, demonstrated a problem with the initial exhaust design. But this exhaust solution was not the “Octopus” as described; in fact McLaren Technical Director Paddy Lowe explained to me at the 2012 cars launch, that “it didn’t look anything like an Octopus”. Adding “The exhaust we had was a slot, we called it a fantail”, which was a simpler, albeit still innovative solution.
During my visit to Mercedes AMG before Christmas, the company set us a challenge that’s been put to other more notable visitors. In the engine build area, two engines were arranged in each bay, but without the coil pack, heat shield and exhausts fitted. Our task was to fit these parts to one side of the engine, along with tightening each fastener to the correct torque setting. A dozen journalists attended the day, the challenge being made even greater as the two current Mercedes AMG drivers had also previously completed the challenge.
The coil pack is handed over and the challenge starts...
The first job was to fit the coil pack. The four-pronged carbonfibre cased unit is a press fit atop each spark plug, then the we needed to connect CAN electronics interface near the front of the airbox.
Next the heatshield goes on... (eventual challenge winner watching intently behind)
A small reflective coated carbonfibre heatshield goes over the coil pack, attached with three small bolts, one of which is smaller and requires a different torque setting.
Access to the 24 exhaust studs under the engine was surprisingly good
Then onto the exhaust system, weighing about 3kg each exhaust is hand made from thin sections of inconnel welded together. Although the 4-into-1 exhaust is one assembly, there is some play in the primary pipes joints with the collector, so fitting the four exhaust pipes to the studs on the engine requires a little fiddling. Each exhaust pipe bolts to the exhaust port with three nuts, two above and to the side of the exhaust pipe, and one centrally below.
A blur of hand movement gets each nut threaded on...
Each of these 24 nuts being tightened to the same torque setting. With the engine up on the stand and being able to kneel below the engine, getting access to each fastener was surprisingly easy, none of the exhaust pipes being particularly obstructive. I’m sure doing the same job with the engine in the car and the floor fitted is a very different story.
A quick check that each nut is torqued correctly and the job's done.
I completed the challenge in 4m 30s and I was satisfied I’d done a good job. However ex Racecar Engineering magazine editor, Charles Armstrong Wilson completed the challenge in an impressive 3m 30s! Even though one (un-named) journalist took as long a 7m 57s, as group us journalists were confident we’d done a good job. But the teams Drivers had soundly beaten us all. Nico Rosberg did the challenge in 3m 15s, while Michael Schumacher did it thee minutes dead!
The job of the F1 engine builder and mechanic is a difficult and skilled one, the skills of the F1 driver are ever impressive and I’ll stick to drawing racecars and not working on them!
Red Bull started the Abu Dhabi Young Drivers test with a mass of aero testing equipment fitted to the RB7. Although the test is supposed to be to assess young drivers, this is the first open test since the season started and teams make use of this time to gather data from the car. In Red Bulls case this was a repeat of tests from last year, where the front wing ride height and wake is being measured by a range of sensors.
Pictures via F1Talks.pl & SuttonImages.com
Airflow around the front tyre is critical with the post-2009 wide front wings. The ever more complex front wing endplates direct the airflow around the tyre. This effect varies greatly with front wing ride height, so that when the wing flexes down under load at speed, the airflow changes. I have learnt from F1 aerodynamicists that the effect of the endplate on flow around the wheel as the wing flexes down, is perhaps more important than downforce gained the wing being closer to the ground. So the Red Bull and also Ferrari tests are critical to understand how the airflow passes around the tyres with varying wing ride height.
Clearly the gains from flexible front wings will be an ever greater performance factor next year. Even though the FIA rules amended for 2011 were even more stringent than in 2010.
In Red Bulls the case the set up consists of three main elements; the aero rake, ride height sensors and the cables holding the front wing.
Wing mounting cables
Wing cables & Nose hump – Picture via F1Talks.pl & SuttonImages.com
Ride Height Sensors
Ride Height Sensor – Picture via F1Talks.pl & SuttonImages.com
Ride height Sensors – Picture via F1Talks.pl & SuttonImages.com
Aero Rake
Rake detail – Picture via F1Talks.pl & SuttonImages.com
My interpretation of how the rig works is: the wing is allowed to deflect at speed to a specific height, this is controlled by the cables from the hump on the nose. By limiting droop, a number of wing ride height settings can be assessed during the runs. Laser ride height sensors both in the centre and at the front and rear of the endplate will confirm the actual ride height and wing angle being tested. Then the rake will take measurements of the airflow. The driver will then run at a fixed speed along the straight, keeping a consistent speed will ensure the data is consistent and the amount of wing flex can be predicted for each run.
This will create an aero map of flow across the wing and with the wing at different attitudes. The data from the tests will be used to confirm CFD\Wind tunnel results and direct the team in deciding how the wing should flex in 2012.
We can now look in detail how the rig is made and how it works.
Cables holding the front wing
During some runs we saw the cables lying loose between the wing and the hump. Which confirms they are cables and not solid rods, as with the rake mountings. Being cables they could not be for measuring wing position, as not being stiff, they would not be accurate enough. With the size of the nose hump and the other equipment to measure ride height, I now believe they are to control the droop of the front wing. Perhaps the test wing is more flexible than the usual race wing in order to achieve more attitudes under load. Its possible the hump contains hydraulics to adjust the droop of the wing to different attitudes during each run. The 2009 Red Bull used hydraulics in the nose to control the then legal adjustable front wing flap, so it’s a proven approach to fit more hydraulics into the nose cone. Being able to alter wing attitude on the move would greatly improve the amount of data gathered from each run. With there being two cables for each wing, one mounted on the main plane and the second on the flap, the wing could be controlled not only in droop but also the angle of attack. So that the wing could reproduce different beam and torsional stiffness of a future wing.
Ride Height sensors
We have seen laser ride height sensors fitted to cars through Friday practices and extra units fitted for testing. For the front wing rig Red Bull ran five ride height sensors on the wing. The central unit is fitted to the neutral centre section of wing. This would measure true wing ride height, as the centre section is relatively stiff and is not part of the deflecting structure of the wing. Then two ride height sensors are fitted to front to the front and rear of the endplate. These would measure the ride height of the wing tips. Using the centre ride height sensor as a base line provides the amount the wing tip is deflecting. Just as with the double cable arrangement supporting the wing, the two endplate ride height sensors would measure any change in angle of attack, the delta between the front and rear sensors showing the wings angle of attack.
Aero Rake
With the wings attitude controlled and measured by the cables and sensors, the wake of the wing is then measured by the aero rake. This is an array of sensors measuring air speed, velocity and perhaps even direction. Two rows of rakes are employed and these are securely mounted to blisters on the nose cone. Just as with the wing mounting cables these struts may be attached to hydraulics to raise the rake over a range of positions, to map a wider area behind the wing. A slightly messy part of the mounting system if the bundle of cables exiting the rake and passing up into the nose cone to be attached to the cars telemetry system.
In free practice for the Indian GP, we saw a violent fluttering of Felipe Massa’s front wing. This is a higher frequency movement than the flex we commonly see on front wings – in fact, the movement is enough to cause the endplates to hit the ground, sending up showers of sparks. Bearing in mind that the wing is around 75mm off the ground when the car is at rest, we can appreciate the amount of movement that’s occurring here.
This movement is not an aero benefit in itself, but may be symptomatic of other flexibility in the wing.
Ferrari Flexi Wings 2011 Indian Grand Prix FP1 by Mattzel89
This clip shows the Ferrari crest the hill before braking into a turn (4s into the clip). As the car crests the hill at high speed with DRS open, it’s clear that the wing is bowed from the aero load. It’s possible to see the side spans of the wing bend down from the central section. At this point there is some vibration in the wing, but not an excessive amount. As the car starts to go down hill (DRS still open) and passes a shadow across the track, the wing starts a rocking motion (5s into the clip). This rocking soon increases in violence until Massa closes the DRS and starts to brake as usual for the corner (at 9s), so this episode only lasts three seconds. I counted around 20 movements of each endplate, which increase to the point where the endplates’ skid blocks strike the ground.
The cause may be explained as follows: the wing is bowed at speed, but as the car crests the hill the wing is unloaded slightly. Then, as the car starts to move down hill, that load would reverse and the wing (which was already vibrating) is sent into a rocking motion. One endplate moves down, while the centre section and wing mounting pylons appear to be rigidly fixed to the car and are not moving. The load passing from the endplate must have been transferred across the central spar of the wing to the other endplate, which now drops. This movement resonates in a wave from one side of the wing to the other, increasing in frequency and amplitude until the wing actually hits the ground.
I can’t explain why closing the DRS and braking calmed this resonance so quickly, but the wing rapidly returns to the low-amplitude, high-frequency vibration seen elsewhere on track.
Also, I’m no expert on composites but my limited knowledge does suggest that carbon fibre structures are relatively well damped (compared to, say, a metal structure), the rebound effect of flex being relatively well damped and not prone to oscillating.
Ferrari introduced the new front wing in Korea. Alonso ran the wing as it was clear that it displayed the accepted level of flex as used by many other teams. The wing is legal as it meets the more stringent FIA 2010 deflection test. Last year Red Bull set a precedent when its wing, which openly appeared to bow downwards at speed, passed the tests and was declared legal, even when the test loads were increased mid-season.
This bowing effect – where the tips of the wing move downwards at speed – is commonly used as the front wing then sits closer to the ground and can generate more downforce. Despite a lot of theories about mechanisms or heat being responsible for the flex, the answer is much simpler: it is down to the way you want the wing to work i.e. the tips to bend down without the wing twisting and thereby reducing the wing’s angle of attack. This is all done with the lay-up of the composites – I’m told it is a “nightmare“ and have heard of composites technicians spending weeks trying different lay-ups to get this effect, but once worked out it is very effective.
Of course F1’s knowledge of carbon structures has been used to create very stiff parts, but now that we are starting to allow controlled flex, we will start to see resonance becoming an issue. There is a new field of knowledge to be understood and controlled.
It seems the wing was tried again in FP3 and the FIA has taken an interest in the wing. The wing was removed and one would assume that it will not be raced for fear of mechanical failure or a post-race ban, although Ferrari’s Friday press release may suggest that the wing is a development item not planned for use in the race, but as part of the 2012 programme. Pat Fry: “We continued with the now usual parallel programmes: on the one hand looking for the best set-up for the car at this circuit and on the other, working to get a greater understanding of the latest aerodynamic updates, with the new car project in mind.”
We have seen extreme movement of front wings before in super slow motion, such as wing tips fluttering, wings swaying sideways on their mounting pylons and endplate devices flapping. All of these movements, although highly visible, have been accepted by the FIA because the tests have been passed. All of which is to the detriment of the overriding regulation that bodywork should be rigid and immovable.
Thanks to Andrew Biddle (andrewbid@gmail.com) for his assistance as Copy Editor
McLaren tested its new front wing in first practice for this weekend’s India GP. The new front wing is a hybrid of the current wing and a revised main plane. McLaren has been alone in running a main plane with two distinct sections; the geometry of the wing is split between the span which sits ahead of the wheel and the inner span which sits in clearer air. This split wing has been run since Singapore 2010 (shown inset on the illustration).
The new wing has a straight mainplane profile, the old wing was split into two section (inset)
The new wing has a straight mainplane profile, the old wing was split into two section (inset)The new front wing maintains a consistent profile across each span, making the wing appear far simpler. Whatever gain the team found from the split design has been won over by the gains from a wider single profile. Perhaps the wake structure of the old split wing worked at the expense of peak downforce, as the new wing clearly has a larger working area as there isn’t the need for the complex join midway across its span.
Clearly the wing now has more working area, without the complex joint
Although the main plane is new, the wing retains its endplate arrangement, with the wing curving down to form the lower part of the endplate, which is near standard practice for this year. The upper part of the endplate is formed by a vane which also mounts the outer cascade winglet. Both the cascade elements have been retained – the ‘r’-shaped double element vane now mounts directly to the wing rather than to the complex metal section joining the two different wing spans.
McLaren McLaren uses two cascade elements: an inner
Thanks to Andrew Biddle (andrewbid@gmail.com) for his assistance as Copy Editor
An excellent Sutton Images picture seen on F1Talks.pl, taken through the aperture on the front of the McLaren has given us a rare chance to see the set up of the front suspension.
(http://www.f1talks.pl/2011/08/25/czwartek-na-spa/?pid=4590).
Typically most teams follow the same set up for the front suspension in terms of the placement of the rockers, torsion bars, dampers anti roll bars and heave elements. As unlike with rear suspension, the raised front end almost dictates a pushrod set up in order to the get the correct installation angle of the pushrod. However the McLaren antiroll bar shows there is some variation in comparison to the norm and also highlights Ferraris similar thinking in this area.
In comparison to my more recent posts, this is not a breakthrough in design, simply a chance to see the teams playing with packaging to achieve similar aims.
Typical front suspension
As an overview of the conventional of the rocker assembly in the attached diagram shows the rockers are operated by the pushrod, a lever formed by the rocker operates each of the suspension elements. Compressing the heave spring and wheel dampers, extending the inerter and twisting the torsion bars.
A typical "U" shaped ARB: Arms connect the torsion bar to the rockers via drop links
Typically teams use a “U” shape anti roll bar (ARB). In this set up the antiroll bar is connected to the rocker via drop links, and then each arm twists the torsion bar when the car is in roll. When the car is in heave (car going up and down, no roll) the ARB simply rotates in its mounts and adds no stiffness to the suspension. Different torsion bars in the anti roll bar create different roll stiffness rates for the suspension. Teams will either switch the entire ARB assembly for a different rate ARB. Red Bull have engineered their ARB for the torsion bar to be removed transversely through the side of the monocoque, in a similar fashion to removing the normal torsion bars.
However McLaren and Ferrari have gone a slightly different route.
Mclarens ARB
McLarens ARB is formed of two blades joined by a drop link
In McLarens case their ARB is a simple blade type arrangement. These blades are splined to each rocker the blades are joined at their ends by bearings and a drop link.
In roll, the blades react against each to create roll stiffness
When in roll the rockers rotate in the same direction, one blade goes down and the other goes up, the stiff drop link transfers these opposing forces and the blades flex. These opposing forces add stiffness to the front suspension in roll.
In heave, the blades move together
In heave the rockers rotate in different directions, both blades move down and the increasing gap between their ends is taken up by the drop link. So the blades do not flex and do not contribute to heave stiffness.
Different thickness blades create different roll stiffness; they must be removed from the rockers and replaced to achieve this.
Ferraris ARB
Ferraris ARB uses two blades joined by an elegant arched guide
Ferrari have used this solution at least since the late nineties, the idea has been seen on older Minardis too. I suspect the idea was taken to Minardi by Gustav Brunner, who may also be the creator of this elegant solution.
Similar to McLaren the roll stiffness is provided by blades splined to the rockers. But the connecting mechanism is instead a single bearing sliding inside an arched guide. Just as with McLaren ARB, when in roll the two ends push against each other to create the reaction force to prevent roll. When in heave the bearing slides through the arc of the guide and no force is passed into the suspension.
Summary
I don’t believe either of these solutions has a compliance benefit over the other. The McLaren\Ferrari systems may be take up a little less space inside the nose and may weigh a little less. But both will be a little more complex when changing the roll stiffness.
Assemblies
Before the Korean GP, I published a proposal for a flexible but legal splitter (https://scarbsf1.wordpress.com/2011/10/14/a-legal-but-flexible-t-tray-splitter-the-see-saw-solution/). This so-called See-Saw arrangement of the T-tray splitter was a response to the need for the splitter to deflect to allow a low front wing ride height, but still meet the FIA tests. It’s design was influenced by unusual wear marks seen on cars at previous races. My blog post was provocative, as I did not personally believe it is legal. But, by playing devils advocate, it was clear a case could be made for the See-Saw splitters legality. I had seen no direct evidence such a splitter is in use in F1 and I had no information suggesting that it might have been used in the past.
It was therefore a great surprise when I was tipped off that the FIA had sent out a Technical Directive (TD) on the matter during the Korean GP weekend. It transpired that a top teams Chief Designer had approached the FIA to propose they wanted to use just such a solution for their 2012 car. In the teams communication to the FIA Technical Delegate Charlie Whiting, the See-Saw concept was drawn and described as a method to ensure the splitter isn’t damaged by contact the ground, thus making the car more reliable and damage prone. The request further explained the reaction force provided by the FIA test rig, allowed the more complaint splitter to still meet the FIA deflection test. This being possible even without a kinematic fixing joint (i.e.not having a moving bearing or pivot as the splitters fulcrum point).
Its not unusual for teams to take this approach in protesting another teams car. Its less confrontational, as they argue the technologies legality, rather directly protesting another team. There have been several instances of this in the past. The team probably weren’t seriously wanting to use the See-Saw splitter, nor did they feel its use was for reliability reasons. More that they were concerned another team were currently gaining an advantage from its use and wanted the design exposed and its legality confirmed.
The FIA’s response was a technical directive, coded TD35. It’s not surprising that it confirmed such an splitter would not be legal. But, crucially the FIA confirmed that they reserve the right to alter the test to ensure the deflection test procedure isn’t being exploited. Therefore future scrutineering checks, may well include an inspection of the splitters mounting and conducting the deflection test with the cars weight bearing down at different points, rather than sat flat on top of its plank.
Several personnel within F1 teams have since contacted me on this subject. Its been suggested that such a construction is, or has been used in F1. The catalyst for this design was the further restriction on splitters after the Ferrari\McLaren protest in 2007. But with the further restriction on splitter mounting and deflection announced at Monza Last year, the See-Saw solution may have become even more useful in 2011.
As yet the change to the FIA testing procedure has not been detailed. Although the Indian GP weekend will be the first chance for the FIA to act on this technical directive with revised checks. It will be interesting to hear if any teams are asked to alter their splitter construction as a result of this.
Another possibility with the Mercedes stalling front wing is that it allows an opportunity to play with the linearity of the cars ride height. In particular the proximity of the splitter to the ground at different speeds. Looking at this in comparison to other possible uses, I would suggest this is a more realistic and beneficial solution than those initial proposed (https://scarbsf1.wordpress.com/2011/10/21/mercedes-f-duct-front-wing/).
As has been much discussed, the front wing needs to run as low as possible to create downforce. To achieve this teams run as lower front ride height as possible. The limitation of a low front wing ride height is the front splitter grounding, this becomes an increasing problem as speed increases and the aero load builds up and compresses the front suspension. So at the ‘End of the Straight’ (EOS) at very high speed the car is at its lowest and splitter is grounding. This forces the car to have a higher ride height, to keep the plank from wearing away in the EOS condition. Thus at lower speeds the front ride height is correspondingly higher, compromising the potential of the wing.
If Mercedes stall the front wing as the car reaches top speed, hence above the speed of any corner on the track. Then when the wing stalls, the load on the front axle will suddenly decrease and the front ride height will increase. Effectively the ride height\speed map is no longer linear. Ride height will decrease linearly at lower speeds, then above the speed of the circuit’s fastest corner, the wing stalls and ride height increases.
What this allows the race engineers to do is shift the ‘ride height curve’ down the map for a lower initial (static) ride height. Knowing that the splitter will not ground in the end of straight condition. Therefore with the unstalled wing having a lower ride height, more downforce can be generated. When the wing is stalled the lack of downforce is less consequential as the car is on the straight. Plus there may still be the small boost in top speed from the lack of induced drag from the stalled wing.
One other potential of such a solution is the front wing grounding. We have seen the midseason version of the Mercedes front wing ground quite easily in some turns this year. So as with splitter ride height, endplate ride height at top speed may become the limiting factor in benefiting from the wing flexing at lower speeds. Stalling the wing on the straight will see the load on the wing decrease and the wing will naturally flex upwards. Giving the opportunity to flex more at slow speeds and have the stall prevent grounding on the straight.
In comparison to the manipulation of the CofP to resolve handling problems I initially proposed, this would be a more likely purpose of the stalling wing. Perhaps more importantly this would be a universal solution, one that other teams could legally adopt in preference to flexible splitters or excessive rear ride height to achieve lower front ride heights.
Note: Updated 24th Oct
Mercedes GP are rumoured to be running a novel front wing. This has been reported in the three major F1 magazines (AMuS, Auto sprint and Autosport). It seems the front wing uses the nose hole to blow a slot under the wing. Although this is a completely passive system (i.e. no moving parts or driver intervention), the fact that it alters aero performance at speed, has seen it dubbed as an F-duct Front Wing.
This solution was first heard of by Michael Schmidt of German magazine ‘Auto Motor und Sport’ (AMuS). Schmidt passed the tip off to Giorgio Piola who spent hours in the pitlane observing the Mercedes car and how mechanics handled the different wings. A task made additionally difficult, as he could not arouse suspicion by Mercedes and give away the fact he was researching the tip off.
He found only two noses had the nose-hole with the splitter and that these wings were only carried parallel to the ground when moved around the pitlane. The final piece of the jigsaw was when he saw a mechanic inspect the wing with his hand leading to understand the slot placement and this information allowed him to work out the system and draw it for the aforementioned magazines. Its remarkable such a tiny detail can be observed and goes to show the hard work that went into Piola exposing this innovation.
Description
AMuS article
As described in the illustrations and texts, the wing assembly (including the nose) is as follows. The nose hole is used to pass air down through the front wing pylons into a slot on the underside of the wing. It appears that the slot has a wide span and is very narrow.
The nose hole feeds air through a duct into a slot under the front wing
This design is somewhat similar to Mercedes early 2010 F-duct rear wing, which was passive. The driver didn’t have a control duct, as with the McLaren system. Instead the ductwork would only blow with enough force to stall the rear wing at a certain airspeed. Tricky to design and tune, this system worked well for Mercedes last year. Its not improbably that just such a system could be made to work on the front wing.
Aiding downforce or stalling the wing?
Typically slots in the wing are for two purposes; aiding or stalling the flow over the wings surface. How the slot creates these two very different effects depends on the slots angle to the wings surface.
To aid the airflow, you need a slot blowing nearly inline with the surface and airflow. Known as Tangential flow, this flat entry angle creates a relatively wide slot when viewed externally.
To stall the airflow, you need a slot blowing at near right angles to the surface. This creates a narrow slot when viewed externally.
Looking at what you need to aid or stall the airflow also requires different placement of the slot.
To aid the airflow, you would inject the flow from the slot in an area downstream on the wings surface where the boundary has slowed and thickened. On a front wing this would arguably be somewhere on the flap towards its trailing edge.
To stall a wing, you want to upset the airflow where it’s moving quite fast, for a front wing it would be placed towards the leading edge of the wing. Last year with F-ducts we saw the stalling slots initially placed on the flap, until Renault placed theirs on the main plane for a better stalling effect.
This analysis suggests the narrow slot towards the leading of the front wing is for stalling not aiding the airflow.
Why stall the wing?
However, while we have got this far in reverse engineering the Mercedes front wing. We now need to work out what the benefit of stalling the front wing is. When stalling aerodynamics there are two possible benefits. Reducing drag for more top speed or reducing downforce.
Drag Reduction
For a front wing the drag loss wouldn’t be that beneficial on top speed. Sitting within the frontal area of the cars silhouette the front wing has very little form drag. However, induced drag from vortices produce particularly at the outboard ends is a factor, but far less than with rear wings. With teams increasingly bending their wings down at speed to gain greater downforce, they are creating most of the load towards the wing tips. By making the wing more aggressive at its outer ends, means that more vortices will be produced and sent around the front tyre. This flow structure creates drag and stalling the wing, especially near the tips would reduce this drag and boost top speed. Martin Whitmarsh was quoted in the AMuS article as suggesting a 5/8kph gain from stalling the front wing.
Drag is induced by the vortices created at the wing tips
With the front wing stalled, some of the energy it robs the airflow can pass towards the underfloor, increasing the pressure at its leading edge, forcing more flow under the floor for more downforce. With more downforce from the underbody, a smaller rear wing can be raced, which also creates less drag for more top speed.
Aero Balance
But that may not be the greater goal of stalling the front wing. Instead the aim may be managing the balance of the car through out its speed range. This would be done by the loss of downforce altering the cars Centre of Pressure.
Firstly, let’s review what the front wing does for the cars dynamics at different speeds. An f1 cars downforce is produced largely by the front wing, rear wing and the floor. With the front and rear wings being the main tuning elements. By tuning the front and rear downforce you alter the cars Centre of Pressure.
Centre of Pressure (CofP) is the balance of downforce at the front and rear axles. As such it’s analogous to being the aerodynamic equivalent of Longitudinal CofG (balance of mass between the axles). CofP is also known as termed as aero balance.
Typically the CofP position closely matches that the CofG. Starting from around 1-2% behind the CofG, then as the car gains speed the car gets lower making the front wing and diffuser work better. Fairly soon the stepped bottom\plank choke flow into part of the diffuser, this robs the diffuser of some downforce. While as the front wing gets closer to the track, it works in ground effect to create even more downforce. The combined effect of the loss of some rear downforce and gain in front downforce is that the CofP moves further forwards.
Such is the potential of the front wing and the near equal tyre sizes front to rear; an F1 car is largely limited on corner entry by the rear grip available. In low to mid speed turns the car needs a slight rear bias to the CofP, this prevents the car suffering corner entry oversteer. Where the car wants to spin as it approaches the apex. Too much front wing in these corners will make the car too pointy and hinder laptimes.
In faster turns the front wing can lead the car. The drivers turn in gentler to fast turns, which creates less lateral acceleration at the rear axle. So it’s rare for the rear to step out on turn-in to fast corners. Thus, at higher speeds you can have a CofP biased towards neutral or the front. Last year with the adjustable front flap, (rather than used for the overtaking balance adjustment for which it was designed) teams would use alter the front flap angle into a fast turn.
So typically you wouldn’t want to shed front downforce for fast turns, by stalling the front wing. Stalling the front wing will reduce front downforce and drive the CofP rearwards, robbing the driver of front axle load just when he needs it.
But, the move towards a rear biased high speed set up could be a response to other problems with the chassis. We knew the 2010 Mercedes W01 suffered understeer and Michael Schumacher didn’t like that facet of its handling, even though Nico Rosberg could cope with it. Perhaps Schumacher’s style of being aggressive on initial turn in, helps the car to rotate into turns more to gain speed through slow\medium speed corners. This tendency corner entry oversteer wasn’t present in the 2010 chassis.
The 2011 W02 is shorter and designed to rotate better, it certainly isn’t a natural understeer. We can suggest this forwards bias, as a possible reason for the car being hard on its rear tyres.
So if the W02 has a forward biased aero balance, this would move the car closer towards corner entry oversteer. We’ve also seen the mid season wing upgrade displays some flexibility, as with many teams front wings. This would have the effect of moving the front wing in yet closer proximity to the track and create even more front downforce at higher speeds.
So with the W02, as speed increases and the CofP moves forwards. Now the corner entry oversteer create a danger of high speed spins, the team need to calm the chassis down a little. So when the wing stalls, the CofP moves rearwards and gives the drivers more confidence with a little understeer. In Michaels case his naturally aggressive turn in is tolerated and as we’ve seen Rosberg can cope with understeer. So both drivers benefit. This might also save the tyres from slip in high speed turns, which could be detrimental to the tyres grip.
Front Ride Height
Another possibility with the stalling front wing is that it’s allowing an opportunity to play with the linearity of the cars ride height. In particular the proximity of the splitter to the ground at different speeds.
As has been much discussed, the front wing needs to run as low as possible to create downforce. To achieve this teams run as lower front ride height as possible. The limitation of a low front wing ride height is the front splitter grounding, this becomes an increasing problem as speed increases and the aero load builds up and compresses the front suspension. So at the ‘End of the Straight’ (EOS) at very high speed the car is at its lowest and splitter is grounding. This forces the car to have a higher ride height, to keep the plank from wearing away in the EOS condition. Thus at lower speeds the front ride height is correspondingly higher, compromising the potential of the wing.
If Mercedes stall the front wing as the car reaches top speed, hence above the speed of any corner on the track. Then when the wing stalls, the load on the front axle will suddenly decrease and the front ride height will increase. Effectively the ride height\speed map is no longer linear. Ride height will decrease linearly at lower speeds, then above the speed of the circuit’s fastest corner, the wing stalls and ride height increases.
What this allows the race engineers to do is shift the ‘ride height curve’ down the map for a lower initial (static) ride height. Knowing that the splitter will not ground in the end of straight condition. Therefore with the unstalled wing having a lower ride height, more downforce can be generated. When the wing is stalled the lack of downforce is less consequential as the car is on the straight. Plus there may still be the small boost in top speed from the lack of induced drag from the stalled wing.
One other potential of such a solution is the front wing grounding. We have seen the midseason version of the Mercedes front wing ground quite easily in some turns this year. So as with splitter ride height, endplate ride height at top speed may become the limiting factor in benefiting from the wing flexing at lower speeds. Stalling the wing on the straight will see the load on the wing decrease and the wing will naturally flex upwards. Giving the opportunity to flex more at slow speeds and have the stall prevent grounding on the straight.
Summary
Looking at the options listed above, I would definitely say the cars wing is stalling. with little to be gained from drag reduction the stalline is most likley to create another effect on the chassis.
In comparison to the manipulation of the CofP to resolve handling problems, the speed sensitive ride height control would be a more likely purpose of the stalling wing. Perhaps more importantly this would be a universal solution, one that other teams could legally adopt in preference to flexible splitters or excessive rear ride height to achieve lower front ride heights.
Legality
So if we now accept that this theory is how the might wing work, we need to look at the legality and construction of the set up. Firstly a passive system that involves no moving parts or driver intervention is legal. Secondly the rules on the closed sections forming the front wing are much freer than those applied to the rear wing. So slots can be legally made across the side spans of the front wing. Clearly it would be legal in both of these respects, that the stalling slot can be made to blow at certain speeds.
The biggest issue is with the nose hole itself. This is covered in the rules and is allowed for the purposes of driver cooling. This being worded into the nose cone regulations for 2009 to prevent Ferrari style slotted noses. We know the nose hole is used to blow the front wing for several reasons. Firstly Mercedes do have the nose hole, but rarely use it, instead the duct moulded into the access panels atop the chassis are normally used for driver cooling. Most of the time the nose hole is sealed up with clear tape.
But one crucial picture in the AMuS gallery accompanying their article, was of the car with the nose removed, showing a black carbon fibre cover going over the front bulkhead. This would seal the nosecone, such that air entering the nose hole would not pass into the cockpit and instead pass down the wings support pylons. With this panel in place the nose hole cannot function as driver cooling and goes against the rules. Perhaps this set up using the nose hole was just at Suzuka for testing, as Teams are unable to do much full scale testing away from the circuit. It could be legally run in a Friday practice session, as teams are given some leeway to test parts which might otherwise be unacceptable to the scrutineers. As long as the parts aren’t run for qualifying, then apparently illegal parts can get limited Friday running.
So for 2012 the wing might gain its inlet from another position. At Suzuka, the use of the nose hole might have been a good way to disguise the system when it was tested.
I have to thank the many people who aided me in my countless questions on this design. Thanks for your patience.
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