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 and\or 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 units\valve 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 moveable\fixed 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 (https://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 (https://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 (https://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 (https://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.

Telemetry and Data Analysis Introduction

During every GP broadcast, we see the drivers sat in the car in the pits, reviewing print outs of the telemetry from previous laps. Using them to understand the car and how to extract better laptimes from it.
Earlier this year an F1 fan offered me a set of telemetry sheets, they found discarded in a Monaco pit garage. These sheets compare the laptime of two team mates around a lap. With this unique opportunity we can start to understand how the driver benefits from this data.

So I had Brian Jee, a ChampCar/IndyCar Data Acquisition/Electronics Engineer to look at the sheets and explain what the data was and how the drivers can review it to see where they lose time compared to their team mate. Brain has written this following analysis to introduce us technical F1 fans to the world of Telemetry and Data Analysis

In order to maintain the teams anonimity, I have deleted the teams, driver, lap time and session details. Please do not speculate as to which team this belongs to, or I will have to remove this thread.

Telemetry and Data Analysis Introduction
Before we can begin to discuss analysis of the data presented on this sheet, we must first understand its origin and purpose.
The software that created this sheet is called ATLAS, an acronym for Advanced Telemetry Linked Acquisition System, developed by McLaren Electronic Systems (MES). ATLAS has become the standard data acquisition package in the F1 paddock due to the use of an FIA spec MES engine control unit on all cars. The entire data acquisition package consists of on-board car data logging electronics and transmitter radio, transmitting data via radio frequency to telemetry receivers in the garages. The receivers decode the data and operate as central servers of the decoded data to distribute it over a local ethernet based network. Any appropriately configured PC computer, running ATLAS software, can simply connect to the network and receive data from the telemetry receiver server. The simple ethernet architecture of the data distribution network also lends itself to an ease of sending the live telemetry back to the factory to engineers and strategists. Data is referred to in two forms; “Telemetry” is live data, and “Historic” is logged data or also backfilled telemetry. The hardware and infrastructure of the system is beyond the scope of this discussion, but is fundamental to understanding how an engineer would receive the data and with what tools he or she would interact with it.

Within ATLAS, we can loosely compare it to Microsoft Excel in reference to its working surfaces. In Excel, most people are familiar with the spreadsheet, as a whole, referred to as a “workbook.” Within that “workbook” are multiple “worksheets” containing any number of user created charts and information. Organization of the working surfaces of ATLAS is similar in that an ATLAS “workbook” contains multiple “pages” organized in a similar Excel tabular graphic user interface. Each page contains user created “displays” on which to analyze data. The printed sample of data we are here to discuss is actually a single selected “display” printed from a “page” in an ATLAS “workbook”, in the same manner that an individual chart can be printed from Excel.

At the top of this printed display we see, ‘StatLapOverlay Monaco.’ This user configurable information is used to aid in organization and titling. StatLapOverlay quickly informs us that this display is a comparison of two different laps. Furthermore, the date, time of day, and event location is noted as well, indicating where and when this comparison was made, not to be confused with where and when the data was necessarily logged.

This particular type of display is referred to as a “waveform.” A waveform display presents data relative to time or distance as the domain of the plot. Most commonly, data is analyzed on a lap to lap basis, most often the fastest laps of a particular outing or session. Here, that is indeed the case as we have data from two cars overlaid in reference to lap distance on the x-axis. Each car’s respective data is identified by color. Here, blue colored data traces from one car are compared to red colored data traces from another car. It is important to keep in mind that the blue car is the primary datum in this comparison and the red car is referenced relative to the blue car. We will discuss the importance of this key element later.

Now we turn our attention to the bottom of the sheet where we find lists of “parameters” in the area known as the “legend.” Each individually named parameter represents the calibrated output of a unique and individual on-board sensor. Additionally, a parameter may represent a “function parameter”, a mathematical output based upon sensor outputs input into mathematical calculations. If a parameter is present in any of these lists at the bottom of the display, its associated trace is displayed in the waveform above.

To the right of the parameters are a red column and a blue column of values. The parameter value column colors are in respect to the parameter traces of their relative color in the waveform above. Within the ATLAS software, the values change as a vertical line cursor moves across the waveform, allowing the user to identify exact values of points on traces. The values we see here are simply where the cursor happened to lie when the display was printed. The vertical line cursor is noted in the illustration below. Within ATLAS, the cursor is scrolled across the waveform by simply moving the mouse from side to side or using the keyboard arrow keys for finite movement.

Now let’s examine the parameters we are presented with. To begin, each parameter is prefixed with a letter denoting the type of unit of measurement of the calibrated output from the sensor with which it is associated. We have the following prefixes:
v = Velocity, positional displacement over a given time
N = Number, quantitative indication
r = Percentage, relativity to a total
a = Angle, geometric displacement about a vertex
p = Pressure, force applied to a reference
M = Magnitude, scalar identity
B = Bit, bit indicator. For example, binary 1 or 0 indicates on or off
T = Time

Continuing examination of the parameters:
vCar Velocity of the vehicle. Units: kph
There are individual rotational speed sensors on each wheel, but due to speed differentials between each wheel due to slip, turning through a corner, and wheel lockup, they do not represent the velocity of the vehicle. Thus, the individual wheelspeeds are input into “function parameter” calculations to accurately determine the velocity of the car, compensating for differences in individual wheel rotational displacement.

NGear The engaged gear number of gears 1 through 7, with neutral gear represented by number 0

rThrottlePedal Throttle pedal position. Units: Percent
The calibrated position output of the throttle pedal is represented as a percent of total driver application mechanically available. Thus, 0% means no driver application, and 100% means maximum driver application.

aSteeringWheel Rotational angle of the steering wheel, relative to steering rack position.
Units: degrees.
In a 0 degree position, the steering wheel is in an exact “straight ahead” position and the steering rack is centered accordingly.

pBrakeR Hydraulic pressure applied to the rear brake system, measured at the hydraulic output of the rear brake master cylinder. Units: Bar

MDiffDemand Torque applied to the differential. Units: Nm

MKERSDemand Torque applied both to and from the KERS MGU. Torque is applied to the MGU under braking for energy harvesting. Torque is applied from the MGU during KERS boost application. Units: Nm

BNRearWingStateControlMode A bit indicator used to identify DRS activation status.
Units: Active or Inactive

TDiff A function parameter that compares laptime as a function of track distance. It facilitates analysis of laptime relative to track position between a datum lap and any other given lap
The nature of these given parameters identifies this waveform as a classic “driver comparison.” All of the driver’s inputs into controlling the car are present and organized in a specific manner that allows them to quickly identify where on track they are gaining or losing time relative to a datum. For example, a driver may be able to quickly identify a specific portion of the track containing a comparative loss of laptime and easily identify that they are braking 10 meters too early into a corner compared to a teammate.

The other information we see above the parameter value columns are user specific identifiers of the data sessions in question, such as date, event location, and driver name.

A track map of Monaco is located in the lower right corner of the display. A dot moves along the track map relative to the vertical line cursor position as a function of track distance, as it moves across the waveform. The location of the dot on the map is a visual aid in assisting the user in quickly identifying the on-track location of trace characteristics. In addition, we see that corners are identified as green and straights are yellow. These features are further visual aids in assisting the user in ease of identifying on-track location of activity in the data traces. The ATLAS software automatically generates the map based upon lateral acceleration and track distance logged data. The green corners are calculated and determined against thresholds of lateral acceleration.

Lap comparison
Now, let’s turn our focus to the waveform plot. The most essential part of the plot is the x-axis. The x-axis scale is user configurable in units of either time or distance. Time or distance will begin at zero origin at the left side of the plot at the beginning of a lap at the track timing line, increasing towards the right, ending at the end of the lap at the timing line. This example of data represents Monaco and as such, we see the x-axis scale begins at 0 meters on the left and ends approximately after 3200 meters on the right. A total lap distance at Monaco is approximately 3340 meters. All data will be defined as a function of the x-axis, indicating where and when a point of data occurred. Most commonly, the x-axis is defined by distance due to the importance of understanding the physical track location of an occurrence in the data and the distance the car travels relative to any occurrence. Scales of distance also facilitate the comparison of cars and drivers. For example, distance will allow us to see how much further into a corner one driver brakes, compared to another driver. We will examine such an example as we continue on with our discussion.
As we examine individual traces in the waveform, let’s begin from top to bottom.
The first trace at the top is rThrottlePedal with its vertical scale identified on the right of the waveform in units of percentage from 0.0% off throttle to 100% full throttle. We can see the negative slopes of when the driver releases the throttle on corner-entry, completely off the throttle mid-corner, and returns back to full throttle through corner exit with positive slopes.
For closer examination, let’s look at the exit of turn 8, Portier, leading towards the tunnel. Achieving a good exit from turn 8 is crucial to laptime because it exits onto a long straight through the tunnel. Red driver tries to re-apply throttle too aggressive on corner-exit, inducing a moment of snap oversteer and subsequently had to lift slightly to regain control of the car at approximately 80% throttle. Blue driver was much more controlled and reapplied throttle in a much more linear controlled fashion, with three instances of slight modulation, and did not have to lift on exit.

The second trace is vCar with its vertical scale identified on the left of the waveform in units of kph from 0.0 kph to 360.0 kph. Trace maximums define the maximum velocity achieved on entry into a corner with subsequent negative slopes of velocity during braking on entry. Trace minimums identify the mid-corner minimum apex speeds and lead to the positive slopes of acceleration on corner-exit and carried throughout the straights.
For closer examination, let’s take a look at turn 1, Saint Devote, through to turn 3, Massenet. Blue carries much more mid-corner speed through turn 1, and maintains the speed advantage through corner-exit and all the way along the straight to turn 3. On entry to turn 3, Red brakes earlier than blue and once again carries less speed into the corner on entry, all the way through mid-corner. Since Red is mid corner at lower speeds, he is then able to apply a return to throttle earlier than Blue on exit.


The third trace is Tdiff with its vertical scale identified on the entire length of the right hand side of the plot, in units of seconds, from -2.400 seconds to 2.400 seconds. This trace is automatically created and calculated by ATLAS whenever layers of data are overlayed. The parameter is always referenced from one layer of data to another. In our example, we see that the color of the trace is blue, indicating that the blue layer of data is our concern and the red layer of data is our reference datum.
The trace begins each lap on the left hand side of the wave form aligned at 0.000 seconds on its scale. As the trace is drawn across the x-axis, it naturally takes on positive or negative slopes and displacement from 0.000 seconds of beginning time. Positive time differentials indicate the driver was slower than the reference driver in displacing a given track distance. In contrast, negative time differentials indicate the driver was faster than the reference driver in displacing a given track distance. The trace is scaled larger than the other traces across the entire waveform, not only to visualize its slight nuances easier, but also because this single trace defines the utility of the entire display. A driver or engineer will be able to quickly identify the greatest time differentials in TDiff and know to focus attention on data where that difference occurs. In our sample, we see that Blue completed the lap at -1.650, meaning Blue’s total laptime was 1.650 seconds faster than Red.
For closer examination, let’s again take a look at turn 1, Saint Devote, through to turn 3, Massenet. Looking for significant TDiff time differentials, we can quickly visualize two occurrences at turn 1 and turn 3 and focus our attention there. The TDiff scale identifies that Blue gained 0.38 seconds through turn 1 and an additional 0.27 seconds through turn 3. From what we learned from examining the vCar trace, we know that Blue was carrying approximately 10kph more speed through both corners, lending to his 0.65 seconds total gained through both corners. As Red’s driver or engineer, they now know that focusing attention on improving the driver or car for the demands of corner 1 and 3 will yield a gain of at least 0.65 seconds. Subsequently, they will try to understand why Blue and Blue’s car is able to achieve those gains and learn from them accordingly, relative to car setup and driving characteristics.

The fourth trace is BNRearWingStateControlMode, indicating DRS activation. The output of the channel is ‘Active’ or ‘Inactive’ and thus binary in nature. When represented as a trace, we see that it is not transient in nature, as compared to vCar or rThrottlePedal. Along the trace, maximum linear values represent DRS activation and minimum linear values represent the rear wing flap in a normal state with inactive DRS. The binary nature of the trace also lends itself to a lack of need for a vertical scale on the left or right side of the plot.
Continuing examination of turn 1, through to turn 3, we see both drivers activated DRS on exit of turn 1 all the way to corner entry braking of turn 3. Both drivers obviously use DRS to capitalize on decreasing drag for as much distance as possible while at full throttle acceleration through the ‘kink’ of turn 2 and into turn 3.

The fifth trace is MKERSDemand, indicating KERS discharge boost and energy harvesting recovery under braking, defined by force in units of newton metres. The purpose of this trace is qualitative in nature only to identify when the KERS system is discharging or recharging. Therefore, a vertical scale is not necessary on the left or right side of the plot to indicate exactly how much force is applied to or output from the KERS system. Minimum values illustrate KERS energy recovery under braking as rotational force applied to the MGU. Maximum values illustrate KERS energy discharged as rotational force applied to the engine crankshaft from the MGU. As with DRS, KERS is most advantageous for lap time in activating when exiting a corner that leads to a long straight. Torque is the key advantage of KERS, so energy discharge should be activated as soon as possible on corner exit.
In discussion of MKERSDemand, we will examine turn 1, from corner entry through to exit. The illustration will also include the pBrakeR trace at the bottom of the waveform, of which we will discuss later, but require now to illustrate energy recover under braking. All you need to keep in mind now about pBrakeR is that the positive slope indicates brake pedal application and negative slopes indicate brake pedal release.

The sixth trace is MDiffDemand, indicating the force applied to the differential, with its vertical scale present on the right side of the waveform, ranging from 0.0 newton meters to 2000.0 newton meters. Discussing the function and operation of electromechanical control of the differential far exceeds the scope of this discussion of an introduction to telemetry. In addition, without full knowledge of the mechanical and electronic control settings of these particular differentials in question, we are unable to engage in a reasonable analysis without assumptions. Therefore, we will simply note the major characteristics of the trace without analyzing the differences between Red and Blue.
Maximum linear values of 2000.0 Nm is present when the car is generally accelerating and traveling in a straight line and maximum torque is being applied by the differential to both wheels, such as in a spool. Negative slopes represent slowing down under braking and turning in towards the apex of a corner as force applied to the differential is decreased and the differential is thus differentiating rotational speed and force between the two wheels to allow the car to rotate. Positive slopes represent when the exiting the corner, turning away from the apex and returning to full throttle. On corner exit, the differential must not only apply as much torque as possible to accelerate the car, but still allow the wheels to separately differentiate in order for the car to continue to rotate out of the corner. Minimum linear values occur at the apexes of a corner, illustrating full open differentiation between both rear wheels in allowing maximum rotation of the car.
In discussion of the MDiffDemand trace, we will again examine turn 1. The illustration will include aSteerWheel, just below MDiffDemand, of which we will discuss later. The only thing to keep in mind about aSteerWheel for now is that concave or convex maxima or minima represent the apex of a corner.

Now we will continue to specifically discuss the seventh trace, aSteerWheel, indicating the angular displacement of the steering wheel by the driver, in units of degrees. The trace’s vertical scale is found on the left side of the waveform plot ranging from a minimum of -100 degrees to 100 degrees. Trace values at or near zero represent the steering wheel in a normal straight position in addition to the car traveling straight. Positive slopes indicate the driver turning right, whereas negative slopes indicate the driver turning left.
Since we are already familiar with the aSteerWheel trace at turn 1, we’ll continue to examine that trace bit further, but also include rThrottlePedal.

Recall from our discussion of rThrottlePedal, when Red attempted an over-aggressive return to throttle on the exit of turn 8. Now that we have discussed aSteerWheel, let’s look back at how that effected steering input.

The eighth trace is Ngear, indicating the engaged driven gear in the gearbox. Ngear’s vertical scale is located on the left side of the waveform plot, ranging from 0 neutral gear to 8th gear. Of course the gearbox only contains 7 forward gears, but the 8 is simply for scalar reference. The trace is “stepped” in nature due to the linear and transitionally steady state nature of gear engagement and selection between gears.
Since we have already discussed the vCar trace relative to turn 1, we will continue to do so and now and include NGear in illustration.

Furthermore in examination of NGear, we can take a look at the impressive downshifting characteristics of an F1 car on entry to the Nouvelle Chicane after exiting the tunnel.

Our ninth and final trace is pBrakeR at the bottom of the waveform plot, representing hydraulic pressure applied in the rear brake circuit. Its vertical scale is on the right side of the plot, ranging from 0.00 Bar to 125 Bar.
It isn’t of concern which pressure trace is used from which hydraulic brake circuit, front or rear, because we are not concerned with defining exactly how much force is applied in any given circuit. We only need to know in what manner the driver applied and released brake application, from a purely qualitative perspective. In the case of this driver comparison waveform, a driver or engineer will be primarily concerned with the shape of the braking trace and the relative track location at which initial brake application begins. Obviously, it is optimal to brake as late as possible into a corner and carry the maximum amount of speed to the apex, carried though to exit. In comparing two drivers with similar cars and setups, both drivers would be expected to brake just as deep into a corner as one another. It is common and essential for drivers to examine comparative braking characteristics to understand why they may not be braking as deep or as hard into a corner as their teammate.
The initial positive slope of a brake application trace is steeply sloped approaching the maximum peak because it is optimum in car performance to reach maximum brake application while maximum corner entry speed and thus maximum aerodynamic downforce is available to assist in braking stability.
Continuing to utilize turn 1 as our example of analysis, we will now include the pBrakeR trace in illustration.

Now that we have applied most of our efforts towards examining turn 1, we can summarize that Blue had to accomplish a lot to gain 0.38 seconds TDif, all in one corner. We learned from our analysis that Blue was more aggressive on entry with higher minimum corner speed and turning in towards the curb as early as possible. His success early in the corner allowed him to return to throttle earlier and activate both KERS and DRS earlier as well, all paying dividends towards lap time.
The reality of this particular dataset is that it was logged during FP1, in which teams treat as a test session, in addition to the green track lacking sufficient grip. Furthermore, we are unaware of mechanical or aerodynamic setups, fuel loads, and tire configurations. Without knowing the parity of the cars, it is impossible to compare the performance of the drivers. A major indicator of non-parity between the cars is the final TDiff comparison between the drivers indicating a lap time difference of 1.650 seconds. We can only realistically compare two drivers in similar cars if they are within a few tenths of each other. In addition, from a full perspective of the lap as whole, Red definitely does not appear to be driving in a manner to set fast lap times, reaffirmed by the significant TDiff time difference. If we were to delve deeper into analysis, we increase the need for more specific details about these two cars and drivers, so as not to make incorrect assumptions about either.
When analyzing data, it is important to remember not to perceive or analyze it as if it was repeatable laboratory data. Race car data analysis is much more complicated than that. Beyond the mechanical variances of the car and environmental discontinuities of the track, the driver is a human being who adapts, makes mistakes, and never drives a lap exactly the same as a previous one. For example, if a driver complains of corner entry understeer, it won’t be literally evident in the data because they would have adapted through driving or adjusting available settings. Properly configured data never lies, but it is only truly a useful tool when combined with discussions with the driver and fundamental engineering knowledge. There is much more to be learned from this waveform, but we don’t have all day long to explain it all.

About Brian Jee
Twitter: @brianjee
Indianapolis based Brian is an Ex Race Engine builder/machinist. But more recently a ChampCar/IndyCar Data Acquisition/Electronics Engineer. Brian is looking for opportunities to use his experience to work in F1.

Renaults New Front Wing

Renault have for some time been the team leading with innovations in front wing design. Renault first introduced the feathered set up on the inner tips of the wing last year, by tapering the slot gap between the flaps. Many teams have already copied the feathered design.

Renaults flap is now split into two

But now Renault have gone even further with the concept. In recent races the team have produced a new take on the flap design. The version raced since Germany has split one of the flaps into two. This along with the slot in the main plane creates a stack of five elements for a small span of the front wings width. But in contrast to other uses of extra slots in the front wing, this is not to create a section producing high downforce. Instead each of these steps is designed to create tip vortices to drive airflow along the Y250 axis.

The main plane also has slot ahead of the bulged section in front of the flap

Teams tend to create the greater amount of downforce towards the front outer wing tips. This pressure distribution reduces the load on the inboard end of the wing, in order to better manage the airflow over the centre of the car. However what teams do want to do is to use the relatively undisturbed airflow along this axis and use it to drive airflow over the centre of the car. A steeper wing towards the neutral 50cm centre section of wing would produce unwanted turbulence and rob the airflow of energy. The bodywork rules do allow for some creativity with the vanes and other bodywork allowed along the edge of the monocoque. Known as the Y250 vortex, as most of the aerodynamic effects are created along a line starting 25cm from the cars centreline (Y= lateral axes, 250mm). Components that work along this axis include the front wing mounting pillars, any under-nose vanes, the T-Tray splitter and the intersection of the front wing and the neutral centre section. Flow structures along this axis drive airflow under the floor towards the diffuser and around the sidepod undercuts. Each with the aim to create more efficient rear downforce.

There are effectively five elements created by the four slots (arrowed)

If Renault created a single front wing element with the same angle of attack, a single large vortex would have been produced. This would be far more powerful and pointed outwards a smaller area downstream on the car. By splitting the wing into smaller separate sections, several smaller vortices are created. These are each of lower energy and are spread over wider area. Perhaps this softer approach creates less sensitivity as the cars attitude changes. It will be interesting if any teams has been able to replicate this design by the time their new bodywork arrives at Spa.