UPDATE: Mercedes F-Duct Front Wing

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 (http://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 heightspeed 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.

Mercedes F-Duct Front wing

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

Autosprint 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 bottomplank 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 slowmedium 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 heightspeed 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.

Mercedes: Innovative Linked Rear Suspension

As we get towards the end of the season we often see teams start to get relaxed with the usual secrecy in the pitlane. This weekend in Korea was no different with several technical details being bared to the cameras for the first time.
In particular was the first picture I’ve seen of the Mercedes rear suspension, http://www.f1talks.pl/?p=11598&pid=6274  (Credit to F1Talks.pl and SuttonImages.com for the picture)
The surprise is that Mercedes appear to have adopted a hydraulic solution for managing rear roll andor heave stiffness. Nothing is new in F1, this solution closely matches the aims of the 1995 Tyrrell Hydrolink system, which I hope to cover in detail in a future blog post. Indeed this is not even new in current F1, as several other teams already run similar and perhaps even more developed systems. But this is the first evidence I’ve had of teams interconnecting the suspension with hydraulics.
I spoke to renowned race car designer and suspension expert Andy Thorby about the use of just such a system, “I think most or all the teams are using linked hydraulic actuators on the corners.” adding “they allow you to tune the attitude change of the car under aero load, independently of corner spring rates” by altering both heave and roll stiffness.

Background
Mercedes were one of the many teams to switch to pull rod suspension for 2011, to gain the aero benefits and a lower CofG. With space at a premium at the back of an F1 car, compromises in packaging the various suspension elements need to be made. At its launch it was clear the Mercedes pull rod arrangement placed the rocker quite rearward, in comparison to other pull rod arrangements which place the rocker towards the front of the gear case. The conventional forward rocker placement, puts the heave spring and antiroll in the space at the front of the gear case, packaged around the clutch.
In Mercedes case the rocker is packaged the other side of the gear cluster, just under the gearboxes cross shaft. This leaves little room for the antiroll bar and heave spring. It does however place the rocker and torsion bars very low for the benefit of packaging, aero and CofG. Albeit these are small benefits, perhaps Mercedes choice of a short wheel base did not leave space for the suspension to be packaged around the clutch, as the gearbox length is a critical factor in wheelbase length.
So left with the lack of space to place either a mechanical heave element or a antiroll bar, it appears that Mercedes have opted to create a passive hydraulic system. This is not to be confused with any form of active suspension or the cars high pressure hydraulic systems, this system will be entirely self contained to remain within the rules on suspension design. As the system reacts only to suspension loads, it is clearly legal and there is no question of interpretation in its acceptance by the FIA.

What Mercedes have in place of a conventional anti roll bar and heave spring are hydraulics units (yellow), which probably also act as the dampers. These are connected via fluid lines (blue) to the central valve block and reservoir (red). Springing for the rear wheels is managed by the torsion bars. One end of which is conventionally located within the rocker pivot, the torsion bar then leading forward and connecting to the front of the gear case.
There is still some hardware at the top of the gearbox, which looks like it might be the mounting for an anti roll bar (ARB). But in this set up, its hard to see how the suspension rocker will act on the ARB. So Its not clear if the car started the season with a mechanical system, or whether it was designed purely with this solution in mind.
The teams early season struggle with rear tyre wear, may or may not be attributable to this system. My feeling is that other rear suspension and car layout factors have influenced the tyre problem, to a greater degree than this hydraulic solution. Although in a car that had a difficult pre-season and fundamental design problems. Getting the hydraulic suspension to work as well, may have been just another drain on resources for a team trying to recover its pace.

How it works
A cars individual wheel dampers displace hydraulic fluid as the suspension moves, creating higher pressure in one end of the damper and lower pressure in the other. To act as a damper, valves in the damper control the rate in which the fluid moves between the two chambers to create the damping effect.

In the passive hydraulic unit, the fluid is displaced not from one chamber to another, but via pipes through a valve block and into the opposite hydraulic unit. How the upper and lower chambers are interconnected left to right make the system react differently to inputs from the suspension. These being a resistance to roll or heave.

In a simplified view we can see the system working in two modes, with the fluid lines in ‘Parallel‘, where one units upper chamber connected to the opposite units upper chamber. Or, in ‘Crossover‘, where the upper chamber in one unit is connected to the lower chamber in the opposite unit.
In each mode we can see the effect of the car in roll (tilting from cornering loads) or heave (going down from aero or braking loads).

Parallel

Heave

When the car is in heave, both upper chambers create high pressure. This creates resistance between the two systems wanting to displace their fluid. This has the effect of increasing the cars heave stiffness.

Roll


When the car is rolling, the upper chamber on one side and the lower chamber on the other side create high pressure. As these chambers are now connected to the lower pressure chambers on their opposite side, the fluid displaced with little resistance. This presents no increase in the cars roll stiffness.

Crossover

Heave


When the car is in heave, both upper chambers create high pressure. As these chambers are now cross connected to the lower pressure chambers on their opposite side, the fluid is displaced with little resistance. This presents no increase in the cars heave stiffness.

Roll


When the car is rolling, the upper chamber on one side and the lower chamber on the other side create high pressure. As these chambers are cross connected to the high pressure chambers on their opposite side. This creates resistance between the two systems wanting to displace their fluid. This has the effect of increasing in the cars roll stiffness.

If a team simply want a hydraulic system to create one suspension effect, then they can rig up a basic system based on one of these patterns. However, with a valve system connecting in the centre of the pipes, then a single pair of hydraulic units and would be able to control both heave and roll stiffness. Such a system would not need external pressurisation or any control software to operate the valve block.

Development issues
However these systems are still present handicaps to development. Friction in the valve seals and the valve block, will create heat and variances in the systems response. This heat will be an enemy of the system, as it effect on the volume of fluid in the system, thus the stiffness the system provides to the suspension will alter. As a result the system will need to be a ‘constant volume’ system. Where the volume of fluid is managed depending on its rate of thermal expansion. This is probably part of the function of the small reservoir mounted to the valve block.
Equally important is the ‘installation stiffness’ of the system, that is the flexibility of any components, especially the flexible fluid lines, as this will alter the systems response.
But these and other issues related to hydraulic systems is already well understood by the teams with similar hydraulics being used both for the braking system and the high pressure electro-hydraulic control systems.

One area which presents trouble to the teams is the modelling of these systems. The design and simulation of the hydraulic element is not necessarily covered by conventional suspension and ride simulation software. I asked , Peter Harman, Technical Director of Deltatheta Ltd (http://www.deltatheta.com) about these issues. “I have advised teams on how best to simulate them“ adding “it sounds like it is a common development“. The problem is the hydraulic elements don’t fit in with conventional suspension design software. As Peter explains “Traditionally car companies have used MSC Adams for suspension modelling, and this has been adopted for ride simulation by most F1 teams, however Adams is really just a mechanical tool and doesn’t do hydraulics well“. Thus teams need to alter their approach, needing specialist add-ons and code to augment the already well established suspension development solutions.
Of course the systems will also be physically rig tested in back to back comparisons with their mechanical counterparts on the teams multi-post rigs.

Overcoming these issues with good approach to the detail design work, a hydraulic system should be able to get very close to the response of a Mechanical system. However the potential of the Hydraulic solution does offer some other benefits over purely mechanical systems.

Other possibilities
Once you have the ability to independently tailor the damping and stiffness of the heave and roll functions. The next obvious step is to control the pitch of the car. Pitch is when the car brakes or accelerates, one end of the car moves down and the other moves up. Braking creates a forward pitch, with reduced front ride height and greater rear ride height. Acceleration is the opposite situation.
As we’ve seen for the past few years controlling pitch is critical to maintaining a low front wing ride height, with out sacrificing splitter wear or excessive rear ride height (thus rear downforce).
Linking the hydraulic unitsvalve blocks between both front and rear axles, will allow the same resistance to pitch, as it does to heave on just one axle. This will increase the front heave stiffness, reducing forward pitch and preventing the splitter grounding excessively. This effect under braking could be further augmented with either gravitationally load sensitive valves, altering the displacement of fluid front to rear. Or similarly, a valve directly controlled by brake pressure. The former G-load system already in legal use on the individual wheel dampers and the latter solution a common fitment to motorbikes in the eighties, often termed Anti-Dive.

Summary
With Rake being ever important to the cars aero set up, such linked systems are increasingly being investigated by the teams. Indeed one team has run such a solution since mid 2009 and at least two other teams (one at each end of the grid) ran them last year.

Ferrari: New Front Wing Analysis (summary)

Ferrari tried out a new Front Wing in Free Practice for the Korean GP.  It’s rumoured to be a 2012 part being tested at the final races of this season.  I will write a fuller analysis over the weekend, but here is the summary of its new features.

In layout the wing is a modern take on the 3 element wing and for the first time at Ferrari features and endplate-less design.  Ferrari wing layout has been largely the same since the 2009 F60.  With the endplate and the cascades attached to it removed.  You can see the wing curls down to form the endplate itself.

Rather than a 3-element wing with a mainplane and two flaps, it is formed of a main plane, which is slotted to create two elements for most its span, with a single flap attached behind it.

The vertical sections of wing forming the endplate, are outswept and overlapping.  This allied to the vane (removed in this pic) aids the flow around the front tyre.

Only the inner section of flap is adjustable.  The outer part of the flap is fixed and cannot be adjusted, nor can the middle element as its formed from the structural main plane.  The adjuster mechanism is visible between the moveablefixed section of flap, the socket for the wrench to alter the front flap angle, is also clearly visible.

Sauber: Suzuka updates

Sauber produced a major upgrade for Suzuka, which comprised of “new front wing, new rear wing, new turning vanes and side pod deflectors, new brake ducts and modifications to the floor”. Most visually different was the front wing which is covered in detail here. But the other upgrades were just as important. The rear wings frontal profile forms a slight “M” shape, with the leading edge being slightly lower at its outer and central points. The sidepods have been revised with a new cooling exit panel and the exhaust tucking back into the coke bottle exit, thus no longer in a Red Bull “outer blown” style.

In detail the front wing sports a new profile and revised endplates. The leading edge forms a fairly flat profile and then lifts into an arc to meet the endplate. In a similar way that Red Bulls wing meets the FIA central section at 90-degrees. As such it aims to achieve the same function to create a strong vortex, in Saubers case to carry airflow out around the front tyre.

The wing is formed of three main elements, the main plane being very short with much longer chord flaps behind it. As is common for most teams now, the flap adjusts cross about 75% of the span. The outer 25% section being at a fixed angle of attack, as it forms part of the endplate. Along the intersection between fixed and adjustable sections of flap, Sauber fit the pod for adjusting the front flap angle (FFA), used during pitstops.

Atop the endplate is the revised vane and cascade arrangement. The vane is now more rectangular in appearance and serves both to direct airflow and meet the minimum side-elevation bodywork surface area for the endplate. To this are fitted two cascade elements, a larger two element winglet and the smaller single element winglet. These downforce producing sections also are angles to aid the general outswept airflow in this area.

McLaren: Suzuka upgrades and design overview

McLaren have proven to be Red Bulls nearest competitor for most of the season. While not quite having the same raw pace as the RB7, the MP4-26 is as fast on race day and arguably can be easier on its tyres. Having started with two bold concepts the “U” shapes sidepods and the mysterious “Octopus” exhaust, the design had to be compromised to ditch the complex exhaust and revert to a Red Bull style outer blown diffuser. Leaving McLaren with a large amount of space under the gearbox, that was supposed to package the exhaust. This left the car with a higher rear CofG without the benefits of the exhaust to offset it. So it’s been remarkable that McLaren have been able to morph the initial concept into a race winning, Red Bull baiting package.
The pace of development never slows, So McLaren arrived at Suzuka with a new diffuser detail and another iteration of its Silverstone short-chord rear wing.

Following a lot of the rest of the paddock , McLaren added a diffuser flap across the top edge of the diffuser exit. The flaps profile only being broken by a large gurney flap under the rear crash structure. As already discussed in the Red Bull Monza diffuser article (http://scarbsf1.wordpress.com/2011/09/22/red-bull-monza-diffuser-analysis/), this flap is an evolution of the trailing edge gurney, used to create lower pressure aft of the diffuser for more downforce. McLaren can run such a large central gurney flap as it sits in a 15cm window in the bodywork rules that allow taller bodywork. Its also beneficial as the raised rear crash structure (for the “octopus” exhaust) allows a good airflow to pass underneath it towards the gurney.

Again we saw McLaren run the short chord DRS rear wing, allowing the team to use the DRS more frequently during qualifying runs. This wing has already been detailed in the blog (http://scarbsf1.wordpress.com/2011/07/14/mclaren-new-drs-rear-wing/).

Further down the car, we can see the rear brake duct cascade. Rules allow 12cm of bodywork inboard of the rear wheels, there is no stipulation that these function as brake cooling ducts, so teams exploit this for ever larger stacks of aerofoil sections to gain downforce directly acting upon the wheels.
McLaren have also altered their exhaust system over recent races, switching from a simple oval profile tail pipes, for pipes that pinch-in to form a nozzle at their exit. Also the detailing around the floor area varies by track, with more or less floor being cutaway around the exhaust exit. This alters the amount of exhaust flow passing beneath the floor to suit differing ride heights. As one of the functions of the EBD is to act to seal the diffuser, often likened to a virtual skirt. The high energy exhaust gas, prevents other airflow entering the diffuser, thus maintaining downforce.
Its no surprise given the proximity of the brake ducts to the exhaust outlets, that the lower stack of brake duct aerofoils are heat protected. No doubt some of the exhausts energy is used to drive airflow under the ducts to create more downforce.

McLaren use a split cooling outlet set up, rather than Red Bull who tend to focus all the outlet area into the large bulged exit high up on the engine cover. McLaren’s main outlets are the exit to the sidepods coke bottle shape. With outlet area to the side of, and above the gearbox. This is aided by 3-slotted louvers on the flanks of the sidepods.

Lastly McLarens unique sidepod design is clear to understand from this angle. The “U” pods create a path for the airflow passing over the centre of the car, to reach the rear wing relative unobstructed. Typically airflow closer to the cars centreline is cleaner and has more energy. This is why designers tend to use this airflow to feed the sidepods for cooling purposes. What McLaren have done is to compromise on the cooling efficiency for greater rear wing performance. The small fin inside the channel is used to create a vortex to main the airflows energy and direction through the channel.

Red Bull: Splitter scandal 2011?

Photo Copyright: Wolfgang Wilhelm/ Auto Motor und Sport

Following on from the Monza footage of the Mark Webbers Red Bull being lifted on a crane over a spectator area (http://vimeo.com/29538310), German Magazine ‘Auto Motor und Sport’ (AMuS) reported that the legality of the front splitter could once again be called into question. The footage shows the wear marks on the skid block (plank) under the car, with the wear focussed across the protruding section of splitter.

Last year Red Bull as well as other teams were suspected of having a flexible splitter. In order to run lower front ride heights to gain more front wing performance, the splitter gets in the way. Making it bend upwards, allows the crucial nose-down raked attitude required to exploit the current rules. So last year the splitter test was made more severe and also included tests to ensure the splitter couldn’t twist to avoid wear.

AMuS suggests the wear on the splitter is limited to this front section of the plank, the splitter ‘bending’ to spread the wear and avoid infringing the rules on post-race plank thickness. (http://www.auto-motor-und-sport.de/formel-1/f1-technik-exklusiv-red-bull-unterboden-illegal-4043971.html).  Wear is evident on the picture (above) of Mark Webbers cars from Monza.  This wear pattern, is backed up by a view of Vettels RB7 being craned off the track at Suzuka (not shown here), which also suggests the wear is focussed to the front 50cm of plank and not merely the leading edge where the FIA measure wear.

When raked, the splitter should wear in a taper from the leading edge

Wear only at the front of the plank is understandable; such is the nose-down attitude of the Red Bull, very little of the rest of the plank is within reach of the ground. But one would expect the wear to take a wedge shape section out of the plank, at an angle similar to the cars angle of rake. Instead the wear is focussed evenly across this front section of floor, indeed this picture suggesting the greater wear is at around 50cm back front the tip of the block.

Looking at the underside of other cars that had been craned off the track at Monza, their wear is across a greater section of plank, with no highspots of wear midway along their length.

Working how Red Bulls unusual wear pattern is created is a conundrum. The wear could simply be the result of going across kerbs during the accidents and doesn’t occur during normal running. Or the wear could be a literal interpretation of the rules, the leading edge meets the FIA vertical load test, but the splitter articulates further back along its length, to present the splitter at a flatter angle to the track to reduce wear and provide a lower front ride height. Such a set up would meet the wording of the rule 3.17.5 on the deflection and construction of the splitter. As the articulation may be at the point where the tail of the splitter meets the chassis and hence not directly affected by the FIA test and inspection of the leading edge of the splitter.

3.17.5 Bodywork may deflect no more than 5mm vertically when a 2000N load is applied vertically to it at three different points which lie on the car centre line and 100mm either side of it. Each of these loads will be applied in an upward direction at a point 380mm rearward of the front wheel centre line using a 50mm diameter ram in the two outer locations and a 70mm diameter ram on the car centre line. Stays or structures between the front of the bodywork lying on the reference plane and the survival cell may be present for this test, provided they are completely rigid and have no system or mechanism which allows non-linear deflection during any part of the test.
Furthermore, the bodywork being tested in this area may not include any component which is capable of allowing more than the permitted amount of deflection under the test load (including any linear deflection above the test load), such components could include, but are not limited to :
a) Joints, bearings pivots or any other form of articulation.
b) Dampers, hydraulics or any form of time dependent component or structure.
c) Buckling members or any component or design which may have, or is suspected of having, any non-linear characteristics.
d) Any parts which may systematically or routinely exhibit permanent deformation.

Regardless, the Red Bull passes the current stringent FIA scrutineering tests and with the precedent set last year, the car is therefore legal.

No further discussions on the subject appeared over the Suzuka weekend, so this doesn’t appear to be an issue. Again it’s left up to the other teams, to find a way to obtain the raked attitude to gain front wing performance, without excessive plank wear.

Thanks to Auto Motor und Sport for the permission to use their photogaphs with in this post.

Red Bull – Singapore Front Wing Upgrades


At this late stage in the season it seems Red Bull are the main team bringing upgrades, in recent races only Lotus, Virgin and Renault have notable developments. Clearly the imagination of Adrian Newey and Peter Promodrou along with the Aero Dept in Milton Keynes are still bringing new ideas to the table.
Although some elements have been seen tested at earlier race weekends, this is the first proper appearance of the new assembly. The wing now features a twisted main plane section and a revised cascade.

The main plane is no longer near horizontal meeting the FIA specification centre section of wing. Instead the wing curls up and intersects the central span at a near 90-degrees. I suspect this shape is to create a vortex along the Y250 axis, which a key area for creating the correct airflow conditions ahead of the leading edge of the floor. With the aim of creating more downforce from the floor and diffuser.

For the streets of Singapore, the team need a high downforce set up, thus the cascade which gained the McLaren style “r” vane in Monza (http://scarbsf1.wordpress.com/2011/09/10/red-bulls-monza-front-wing/ ), has now been extended with a large downforce producing section. Unlike the kink in the main plane, the inner end of this cascade has an elliptical section which aim to reduce vortices created at the wing tip, sending a cleaner wake downstream.

Red Bull – Monza Diffuser Analysis


Red Bull appeared in Monza was a further development of their diffuser. Changes largely appeared to be focussed on the treatment of the trailing edge of the bodywork. For Monza the diffuser gained a flap around almost the entire periphery of the trailing edge.

Highlighted in Yellow, RBR had a flap spanning around most of the diffusers trailing edge

This flap has been used above the diffuser since the start of the season, but the flap has been narrower, being only fitted in-between the rear wing endplates. As explained in my analysis of the floor as seen at Monaco (http://scarbsf1.wordpress.com/2011/06/08/red-bull-monaco-floor-analysis/ ).

Many pictures were taken of the flap now extending around the sides of the diffuser, which I tweeted about during the Monza GP weekend. But it was the fan video taken during the race, as Mark Webbers stricken RB7 was craned off the track that has shown the floor in greater detail. The video posted on Youtube.com by atomik153 and seen here (http://youtu.be/swoomrzECdM ). This clearly shows the floor from about 3m 40s into the clip. Obviously this must have been unpleasant for Red Bull as the floor is so clearly visible, I know that the other teams have seen this clip. Many fans having seen the detail at the back of the diffuser and suggested the slot created around the diffuser was some form of double diffuser or cooling outlet. While the pictures might suggest this, the slot is merely the gap between the aerofoil shaped flap and the diffuser.  This following illustration shows how the flap is actualy shaped.  There are two parts; the new curved side sections and the pre-existing top sections.

When exploded, you can appreciate how the new bodywork forms a flap around the diffuser

Diffuser trailing edge theory

Few ideas in F1 are new, merely older ideas reinterpreted and expanded upon. This flap is not a new idea, its merely an extension of the gurneys teams have been fitted to the trailing edge of downforce producing devices since the sixties. Gurneys have been added to the end of a diffuser to aid the low-pressure region above and behind the diffuser. This practice has been increasingly important with the limit on diffuser height and other rules banning supplementary channels such as the double diffuser. As far back as the late nineties teams replaced this gurney with an aerofoil section flap. Notably Arrows and latterly Super Aguri used flaps placed above the diffusers trailing edge.

The need for this sort of treatment at the back of the diffuser might at first be confusing. A diffuser is a part of the underfloor, by accelerating air under the floor, low pressure is created and thus downforce is generated. With so many restrictions on the geometry of the floor and diffuser, teams cannot simply enlarge the diffuser for more performance. So they are forced into working different areas of the device harder for the same effect. One area is maximise pressure ahead of the floors leading edge, the other is the lower the pressure behind the trailing edge. This helps flow out of the diffuser, to maintain mass flow under the floor. Although the rules limit the height of the diffuser, this is only the height below the tunnels to the reference plane. Teams have a small amount of space above the diffuser for bodywork and the common gurney fits into the area. Gurneys work by creating a contra rotating flow behind the upright section, this creates low pressure and helps pull airflow from beneath the wing. On a diffuser this has the same effect as a slightly higher diffuser exit.

A gurney creates low pressure by the contra rotating vortcies behind the gurney

The gurney can work above the diffuser, as teams have been paying so much attention to getting high pressure air over the top of the diffuser. This airflow is used to drive the vortices spiralling behind the gurney flap. The better the airflow over the diffuser to the gurney the more effective it can be.   However Gurneys cannot be infinitely increased in size and still maintain their effect. As the gurney gets too large the dual vortices break up and the low pressure effect is lost. Many teams have found this limit this year and have moved to the next solution which is a perforated gurney.

A perforated gurney can be larger as it's offset from the diffuser allowing airflow to pass under the gurney

This is a similar vertical device fitted to the diffusers trailing edge, but there is a gap between the bottom of the gurney and the diffuser. Airflows through this gap to create the distinctive contra rotating airflow behind the gurney. Again this has the same effect as creating a larger diffuser exit and hence creates more downforce.

An aeroil shaped flap can be larger and more efficient than a Gurney

While the gurney is a relatively blunt solution, Such is the quality of the airflow over the diffuser now that teams are able to fit a more conventional aerofoil shaped flap above the diffuser for a similar effect. Without the contra rotating flow of the gurney this solution can be scaled up, as long as the flow to the flap is maintained. Many teams have this solution fitted along the top edge of the diffuser. Although Red Bull are the only teams to have fitted to the side of the diffusers trailing edge. Increasingly teams are seeing the diffuser exit as a 3D shape, the diffuser not only diverges vertically at the exit , but also laterally. No doubt exhaust blowing does allow some of these devices to be effective.

In Detail: The flap on Red Bulls diffuser

We can expect its use to be expanded for next year with larger flaps above the diffuser and flaps around the entire periphery of the diffuser. A long with Rake this will be a critical design feature for 2012, as a result sidepod design will become one of the critical factors in aero design, making sure the top of the diffuser is fed with good airflow. As so few other areas provide potential gains for improving aero efficiency.

Other notes on the Red Bull Floor

Fences

Red Bull fit three fences in each side of the diffuser, these prevent different pressures regions migrating from one side of the diffuser to another. They help maintain downforce and sensitivity. Its interesting to note the fences are not triangular in side profile, I.e. that they don’t meet at the kick line between the floor and diffuser, instead they start a few centimeters behind the axle line with a rounded vertical leading edge.

Starter Motor Hole


As mentioned in the Monaco RBR floor analysis the starter motor hole is blown by ducts in the upper side of the floor. This injects some energy into the flow in the middle of the diffuser. This so called boat-tail section is where the steeped underbody merged with the higher step plane. With the lower centre section and plank, getting airflow into the area is difficult and separation can easily occur if the angle of the floor is too steep. Having the starter motor hole blown helps maintain airflow in this area.

Metal Floor

Exhaust Blown Diffuser Flow

Red Bulls Monza Front wing

Red Bull have appeared at Monza wit the expected specialist low drag wings. However their front wing sports a new detail inspired by McLaren. The “r” shaped inner cascade, has been a feature of McLaren since late last year. This feature has also been used by Sauber.
The horizontal section will probably directly produce some downforce while the vertical sections is more likely to act like a turning vane to direct the general airflow outwards.
For this race Red Bull use a simpler three element wing, with the trailing edge of the flap cut back to create a shorter chord for less downforce.