McLaren: Indian Front Wing Analysis

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

Front Anti Roll Bar Solutions

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 McLarenFerrari 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

UPDATE: “See-saw” Splitter, FIA issue a Technical Directive

Before the Korean GP, I published a proposal for a flexible but legal splitter (http://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 FerrariMcLaren 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.

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.