Publications: F1 Race Technology Report

Every year High Power Media, who publish ‘Race Engine Technology’ (RET) Magazine, produce a number of magazine format Race Technology Reports. Covering F1, Moto-GP, Nascar, Drag racing and 24-hour racing.

Just out is the current F1 Race Technology issue, covering Technical subjects from 2011 and 2012.

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McLaren MP4-26 2011 – Fan Tail (Octopus) Exhaust

McLaren went into 2011 with an aggressive design strategy, this was a response to the poor initial form in 2010 and resulted in the dramatic “U” sidepods and a mysterious exhaust system.


It was this exhaust system that stole most of the column inches in the F1 press and the fan forums during pre season testing. One particular column fed the interest around the exhaust and christened it the “Octopus”. The article suggested the exhaust was ducted to several exits and used high temperature Glass Ceramic Carbonfibre (GCC). It went on to explain the unreliability of the exhaust solution was due to the heat making it fail.
It was true McLaren’s first tests, even from the first private shakedown runs before the public testing had started, demonstrated a problem with the initial exhaust design. But this exhaust solution was not the “Octopus” as described; in fact McLaren Technical Director Paddy Lowe explained to me at the 2012 cars launch, that “it didn’t look anything like an Octopus”. Adding “The exhaust we had was a slot, we called it a fantail”, which was a simpler, albeit still innovative solution.

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Abu Dhabi Test: Red Bull Aero Rake

Red Bull started the Abu Dhabi Young Drivers test with a mass of aero testing equipment fitted to the RB7. Although the test is supposed to be to assess young drivers, this is the first open test since the season started and teams make use of this time to gather data from the car. In Red Bulls case this was a repeat of tests from last year, where the front wing ride height and wake is being measured by a range of sensors.

Pictures via F1Talks.pl & SuttonImages.com
Airflow around the front tyre is critical with the post-2009 wide front wings. The ever more complex front wing endplates direct the airflow around the tyre. This effect varies greatly with front wing ride height, so that when the wing flexes down under load at speed, the airflow changes. I have learnt from F1 aerodynamicists that the effect of the endplate on flow around the wheel as the wing flexes down, is perhaps more important than downforce gained the wing being closer to the ground. So the Red Bull and also Ferrari tests are critical to understand how the airflow passes around the tyres with varying wing ride height.
Clearly the gains from flexible front wings will be an ever greater performance factor next year. Even though the FIA rules amended for 2011 were even more stringent than in 2010.

In Red Bulls the case the set up consists of three main elements; the aero rake, ride height sensors and the cables holding the front wing.

Wing mounting cables

Wing cables & Nose hump – Picture via F1Talks.pl & SuttonImages.com

Ride Height Sensors

Ride Height Sensor – Picture via F1Talks.pl & SuttonImages.com

Ride height Sensors – Picture via F1Talks.pl & SuttonImages.com

Aero Rake

Rake detail – Picture via F1Talks.pl & SuttonImages.com

My interpretation of how the rig works is: the wing is allowed to deflect at speed to a specific height, this is controlled by the cables from the hump on the nose. By limiting droop, a number of wing ride height settings can be assessed during the runs. Laser ride height sensors both in the centre and at the front and rear of the endplate will confirm the actual ride height and wing angle being tested. Then the rake will take measurements of the airflow. The driver will then run at a fixed speed along the straight, keeping a consistent speed will ensure the data is consistent and the amount of wing flex can be predicted for each run.
This will create an aero map of flow across the wing and with the wing at different attitudes. The data from the tests will be used to confirm CFDWind tunnel results and direct the team in deciding how the wing should flex in 2012.

We can now look in detail how the rig is made and how it works.

Cables holding the front wing


During some runs we saw the cables lying loose between the wing and the hump. Which confirms they are cables and not solid rods, as with the rake mountings. Being cables they could not be for measuring wing position, as not being stiff, they would not be accurate enough. With the size of the nose hump and the other equipment to measure ride height, I now believe they are to control the droop of the front wing. Perhaps the test wing is more flexible than the usual race wing in order to achieve more attitudes under load. Its possible the hump contains hydraulics to adjust the droop of the wing to different attitudes during each run. The 2009 Red Bull used hydraulics in the nose to control the then legal adjustable front wing flap, so it’s a proven approach to fit more hydraulics into the nose cone. Being able to alter wing attitude on the move would greatly improve the amount of data gathered from each run. With there being two cables for each wing, one mounted on the main plane and the second on the flap, the wing could be controlled not only in droop but also the angle of attack. So that the wing could reproduce different beam and torsional stiffness of a future wing.

Ride Height sensors


We have seen laser ride height sensors fitted to cars through Friday practices and extra units fitted for testing. For the front wing rig Red Bull ran five ride height sensors on the wing. The central unit is fitted to the neutral centre section of wing. This would measure true wing ride height, as the centre section is relatively stiff and is not part of the deflecting structure of the wing. Then two ride height sensors are fitted to front to the front and rear of the endplate. These would measure the ride height of the wing tips. Using the centre ride height sensor as a base line provides the amount the wing tip is deflecting. Just as with the double cable arrangement supporting the wing, the two endplate ride height sensors would measure any change in angle of attack, the delta between the front and rear sensors showing the wings angle of attack.

Aero Rake


With the wings attitude controlled and measured by the cables and sensors, the wake of the wing is then measured by the aero rake. This is an array of sensors measuring air speed, velocity and perhaps even direction. Two rows of rakes are employed and these are securely mounted to blisters on the nose cone. Just as with the wing mounting cables these struts may be attached to hydraulics to raise the rake over a range of positions, to map a wider area behind the wing. A slightly messy part of the mounting system if the bundle of cables exiting the rake and passing up into the nose cone to be attached to the cars telemetry system.

Pitstop set up adjustments during the race

During most races we see the mechanics make adjustments to the car during pitstops. During each stint radio communications between the driver and his race engineer will discuss the cars balance. Whether the car tends to oversteer or understeer. Since the ban on active technologies there’s little the teams can do to alter the car during the race. Currently only front wing adjustment, rear wing gurney removal and tyre pressures are easily changed during the hectic 3-4s pitstops.

Front wing adjustment

Front Flap Adjuster (arrowed)

This is the most flexible and simplest adjustment, during the stop the mechanics can raise or lower the front flap, via threaded adjusters in the mountings. Known as FFA (front flap angle), a greater angle will reduce aero induced understeer and less FFA similarly reduces oversteer. The race engineer will call for the mechanics to make so many ‘turns’ of wing. A ‘turn’ is quite simple a 360-degree rotation of the adjuster screw. One teams ‘turn’ will not necessarily be the same as another teams, as the wingadjuster geometry will be different for every team.
Teams have historically used a cranked handled wrench for this purpose, although teams have recently been using cordless drill type adjusters. The collar of the drill modified to quickly deliver a specific number of turns, which are pre-set into the collar mechanism.
Between 2009 & 2010 drivers had the option to use the adjustable front wing flap mechanism. Allowed in the rules in 2009 as a pre-DRS overtaking aid. Although the idea did not really aid overtaking, teams did use it for the driver to alter balance during practice and in race stints.

Rear wing adjustment

A 'taped-on'Gurney flap (arrowed)

Although common in US single seat racing, rear wing adjustments are not common in F1. No team runs a threaded flap angle adjustment mechanism, preferring multiple ‘holes’ in the endplate to screw the flap into or machined inserts providing similar adjustment. In rear wing parlance, a ‘hole’ is also one unit of wing adjustment, similar to a turn of FFA. Clearly unfastening, repositioning and re-fastening a rear flap is impractical in a pit stop. However rear downforce is also tuned via the gurney flap, an “L” shaped strip along the trailing edge of the rear wing. By switching the gurney for a taller or wider strip, downforce can be increased. These strips are attached simply by tape, so are quickly removed. However fitting one does take time, requiring the wing surface to be clean and often heat guns are used to ensure the adhesive tape is sticking properly. Due to this, in the race teams are largely faced with the only option of removing a gurney and not adding one. Typically teams will add a more powerful gurney for a wet race, if the race dries then the teams will remove it. Less gurney will also decrease drag slightly and hence boost top speed.  Removing a gurney is a relaiutrvely simple process, as the strip is taped to the wing only via its leading edge.  The mechanic standing behind the wing pushes the gurney forwards and then rip sits off at an angle, taking the tape with it.
In the 2011 Suzuka Grand prix Felipe Massa was reporting understeer and his race engineer Rob Smedley radioed “Ok, we will do that rear wing thing”. At Massas subsequent pitstop, the rear wing gurney was removed. Reducing rear downforce to balance the car.

http://www.f1talks.pl/?p=11461&pid=5892

A Ferrari mechanic attaching a gurney with tape (via F1talks.pl & sutton images.com)

Tyre pressure adjustment

Wing adjustments are largely affecting medium to fast turn performance, at lower speeds the wings are less influential and the mechanical grip needs to be altered. Since the 1994 ban on active technologies, the drivers have no ability to alter the cars suspension. Before that drivers typically had the option to alter anti roll bar stiffness from levers in the cockpit.
So now the teams are left with just the option to alter tyre pressures in the race. Just as with wing adjustments, tyre pressure changes at the front or the rear alter balance. Again ahead of the pitstop the driver and race engineer will agree the change and the new set of tyres will be prepared in advance, pressurised to the right PSI.
During the 2005 season with no tyre changes teams had the mechanics with back pack mounted nitrogen cylinders, as the car stopped for refuelling, the mechanics would rapidly alter the tyre pressures to change the balance of the car.

Other changes during the race
While major balance changes are possible with wing and tyre pressure changed only at the pitstops, the driver does have some other methods to alter the cars balance, from the cockpit. Brake bias is a common adjustment allowing the driver to alter the brake bias front to rear. This can alter the turn-in to corners, as well as tune brake temperatures and locking wheels.
KERS harvesting (charging the batteries under braking) will also have a similar effect as brake bias. Drivers can alter this setting from the steering wheel.
More influential is the differential; this will alter the car at all three points in a turn; entrymidexit. A tighter differential will aid traction out of turns, but induce understeer going into them. Drivers will be altering each of the three settings to get the correct, mechanical set up to balance the car.
One area that’s been much talked about this year is the engines overrun settings. But these settings have been used for much longer to manage corner entry balance. How the engine behaves when the driver is off the throttle going into turns affects the rear tyre grip. A stronger overrun setting will create more engine braking, dragging the rear axle slightly on turn in. Which can make an oversteering the car more stable. Conversely softer overrun setting will suit an understeering car.
Lastly throttle and engine maps will affect the car on corner exit. Intuitively fiercer maps will make a car want to oversteer out of turns, offsetting understeer.

McLaren rear end: Exhaust, cooling and suspension

 

A ScarbsF1 follower in the Melbourne pit lane sent me these exclusive pics. We can see the McLaren stripped in the garage. There’s a huge amount of detail to take in, The key details are the missing exhaust heat shielding, cooling ducts and suspension detail.

We can see the exhaust system is missing in the picture. However there’s a lot of grey heat shielding around the floor giving us some clue to where the flow is going. Notably at the side of the engine where the main exhausts will sit and beyond exit to the sidepod. I can also see heat shielding above the starter motor hole, which is a rounded profile further suggesting this will be subject to fast exhaust gas flow. There’s a curious bulge in the tail of the coke bottle shape. This would be next to the exhaust collector and unlikely to be a good place for sensors, so it’s a mystery why this shape is there.  So we can see potentially an exhaust route blowing out of the back of the sidepods, some of this flow passing under the gearbox to the starter motor hole.  This seems innocuous enough, as long as the gas finds its own way to these areas.  Continued rumours around the pitlane suggest bodywork is used to duct flow to these areas, which would be a contraversial solution.  Only when the car is fully built and scrutineered will we fully know what the solution is.

As already explained in this blog (http://scarbsf1.wordpress.com/2011/02/16/mclaren-roll-hoop-and-cooling-arrangement/) the roll hoop fulfils several function for engine air feed and cooling. We can see the main airbox, beneath it the KERS cooler and its exit duct wrapping around the airbox. At the rear of the airbox is the gearbox oil cooler. The oval exit duct for this cooler isn’t fitted in this picture.

Lastly the pullrod suspension can be seen, the rocker and some of the springdamping set up is down low on the gearbox. A small detail is the shaft and rocker merging vertically from the gearbox, (beneath the silver pipe with blue connector). This might either be the heave damper or inerter, placed higher up for better access, or it might be the pre-load adjuster for the torsion bar (if torsion bars are fitted).

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Trends 2011 – Exhausts and Diffusers

This year the technical talk has largely been about exhausts.  How teams have adapted to the ban on double diffusers and the added restriction on Exhaust blown diffusers. Just to aid understanding going into the new season, I have explained how these solutions work and how they look from beneath.

Double Diffusers

Force India 2010 Double Deck Diffuser (DDD)

Since 2009 the regulations regarding the floor have been interpreted in a literal sense to allow the double deck diffuser (DDD). Indeed the very same rules were exploited to a lesser extent under the previous rules, but this only produced small extra channels in between the outer and middle diffuser tunnels. With the major cut in aerodynamic aids for 2009, several teams sought to find a way to gain more expansion ratio from the smaller diffusers. In essence the loophole exploited the definition of surfaces formed between the step and reference planes. Multiple surfaces allowed fully enclosed holes, which fed the upper diffuser deck that sat above the 175mm lower diffuser. This allowed diffuser to be significantly larger in order to create more downforce. Notably Brawn, Williams and Toyota launched 2009 cars with DDDs. Other teams soon followed suit in 2009 and last year every car exploited the same loophole. Over the winter the FIA acted to close the loophole, by enforcing a single continuous surface across a 90cm span under the floor. In a stroke this banned the double diffuser, there being no scope to create any openings in the floor to feed the upper deck.

Single Diffuser

Double Diffuser

 

Exhaust Blown Diffusers
Another approach to regain lost downforce was the re-invention in 2010 of the exhaust blown diffuser (EBD). This used high energy exhaust gasses to blow the diffuser, the faster throughput of flow under the floor increased downforce. Two methods of EBDs were used in 2010, one blowing over the diffuser and the second blowing inside the diffuser. This latter solution was more effective at driving flow through the diffuser and created more downforce. However this necessitated a hole made into the diffuser to allow the exhaust gas to enter, I‘ve termed this method an ‘open fronted diffuser‘.

2011: No openings allowed in the yellow 90cm zone, outside certain holes are permitted

A by product of the 2011 rules intended to ban the DDD, also stopped this open fronted diffuser solution. However the rules enforced the continuous surface only across a 90cm width of floor and the diffuser is allowed to be 100cm wide. Thus a 5cm window was allowed each side of the diffuser.

Outer Blown Diffuser – Solution

Red Bull Diffuser: Flow passes under the outer 5cm of floor into the diffuser

Red Bull and Ferrari appear to have found this loophole simultaneously. Recently Sam Michael pointed out this was probably the most efficient way to blow the diffuser under the new rules. As Red Bull appeared with this set up first, its often termed the Red Bull Blown diffuser.

What these teams have done is to open up the floor 5cm either side of the diffuser, then route the exhaust towards this opening. The exhaust gas gets collected by the coved section of floor and this directs the high energy gasses under the diffuser, to recover some of the losses from the more open diffuser allowed last year.

Front Exit Exhaust

Renault Front Exit Exhaust: Flow passes wide around the floor before entering the diffuser

Renault meanwhile turned the problem on its head. As the aim of the EBD is to increase flow under the car, they pointed their exhaust at the front of the floor. I’ve had it confirmed to me by two ex-Renault sources that the exhaust does indeed mainly flow under the floor.

The exhaust pipe outlet sits above the step plane just ahead of the leading edge of the floor. This is not simply blowing out horizontally and across the floor, but is ducted slightly to blow downwards and backwards, this is roughly in line the with the flow trailing off the “V” shape above the splitter. Along with the strong vortices set up by the splitter, vanes and bargeboards, this makes the floor appear wider than it is. The flow will go out beyond the floor and then curl back in and under the floor. Some flow will inevitably pass over the floor, but the most of the energy will be driving more flow under the floor to the diffuser.

McLarens Slit Exhaust

The slit above the floor is visible. Copyright: Liubomir Asenov

No conversation about exhausts this year, would be complete without some speculation about McLaren. Amongst the several exhaust systems run by McLaren over the pre-season tests was a “slit” exhaust. This appeared at the first Barcelona test, but did not seem to appear for the second Cataluña test. The exhaust collector could be seen to duct towards a double thickness section of floor ahead of the rear wheels. This section was also interesting for its longitudinal slot, this slot was not large enough to be the actual exhaust outlet, This might be a cooling slot, or to improve the flow from above to beneath the floor.  I beleive the Exhaust is actually below the floor.  As when the car ran the same floor with a conventional exhaust outlet, there appeared to be a removable section of floor ahead of the rear wheels. Being just outside of the 90mm opening rule, the floor ‘could’ be opened to allow an exhaust to blow through to underneath. If sculpted correctly, the exhaust could be ducted back inboard and blow towards the diffuser from under the floor. It’s possible that this could be in interpretation of a legal opening, assuming it met the maximum fillet radius rules.
I’d expect the resulting exhaust outlets to be a long wide slot, this wider outlet would be needed to meet the maximum radius rules and also reduce the back pressure from the tight curve of the exhaust outlet. As the exhaust would have a tortuous bend, to curl back under itself to direct the flow inboard, rather than out wide around the rear tyre.

Mac Slit: The exhaust might exit beneath the floor in a long narrow outlet

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Floors and Diffusers – The basics explained

An F1 car is a complex vehicle, a lot of emphasis is placed on the things we can see, the wings and bodywork. Sometimes we can talk about less visible items such as engine, gearboxes, suspension or even electronics. But perhaps the least visible and detailed part of the car is the underbody. The floor and diffuser, that together create nearly half the cars downforce, for almost no drag. Underbody aerodynamics have been the key to F1 car’s ever faster laptimes. All we ever see of the underbody is the exit of the diffuser and sometimes, if seen from a low angle, the step under the cars floor. To aid explanations in my other articles on underbodies, I have summarised and simplified what the underbody consists of.

Reference plane

Reference plane: Red

This is the datum for the cars dimensions and is effectively the lowest part of the cars floor. When the old flat bottom regulations, dating back to the banning of ground effects in 1983 were revised in the wake of Senna’s 1994 crash, the floor has had to have a step along its length. So we see the stepped shape of the car in frontal profile, with the reference plane sitting lowest in the middle of the car. This step cannot be wider than 50cm or narrower than 30cm, the reference plane must by flat and run continuously from behind the front wheels to the rear axle line. The Reference planes leading portion, also forms the splitter, also known as the T-Tray or Bib.

Step plane

Step Plane: Yellow

Above the reference plane is the step plane, this is effectively the underside of the sidepods. This must sit 5cm above the reference plane. Again the surface must be flat and run from the complex regulated bodywork zone around the front of the sidepods to the rear axle line. A large clearance is mandated around the rear wheel to prevent teams sealing off the floor against the rear tyres.

Step or Transition

Step: Orange

In between the reference plane and step plane, is the step itself or transition. Simplistically there must be a vertical surface in between these two planes. Any intersections of these surfaces are allowed to have a simple radius to be applied, with a 2.5cm radius on the step plane and a 5cm radius on the reference plane.

Plank

Plank: Brown

Not considered part of the floor for measurement purposes, the plank is a strip of wood placed under the car to enforce a minimum ride height. The FIA technical term for this part is the skid block, although this term is rarely applied. Holes in the plank allow the cars reference plane to sit directly on the FIA scrutineering jig, for legality checks over the course of a GP weekend. Titanium skid blocks are allowed to be fitted in certain places in the plank and their wear is measured to ensure a car is not grounding from excessively low ride heights.
The plank can be made in two parts to make removing the floor easier, bit the front section must be at least 1m long. This must be made of a material with a specific density, to prevent excessivley heavy or hard planks producing a performance benefit. Typically the plank is wood based, eiterh jabroc a laminate of beechwood, although more exotic blends of woods and resins not unlike MDF have been used. The plank is 30cm and 5mm thick, any holes made into it must conform to a FIA template.

Diffuser

Diffuser: Yellow

A purely flat floor would probably produce lift rather downforce, so the rules have allowed a diffuser to be fitted to the rear of the underbody since 1983. Before that date there were no rules demanding floor dimensions and diffusers were the full length ground effect tunnels that typified the wing cars of the late seventies and early eighties.
A diffuser creates downforce by creating a pressure differential, with low pressure beneath and higher pressure above. The larger a diffuser is, the more expansion ratio is has, thus more potential to create downforce. Diffusers were limited to a simple 100cm width, 35cm length and 17.5cm height from 2009. Then for this year the height further reduced to just 12.5cm. This massively reduces the potential of the diffuser to create downforce compared to the previous rules. Diffusers are allowed to have fences, but the fences and the diffuser itself must not form undercuts when viewed from below. Which is why we see the simple vertical fences and jelly mould curvature.

Other rules around floors
Overriding all of the above rules are broader regulations covering holes and flexibility. No unsprung part of the car can be visible from below the floor. Typically this means anything, but the suspension and additionally the wing mirrors. This means that no holes can be made into the floor to let flow in or out. The underbodies surfaces are termed bodywork within the rules, there is no term ‘diffuser’ or ‘wing’ mentioned in the rules. Just as with any bodywork in the rules, these parts are not allowed to move or flex. For the floor in comparison the wings, there are few deflection tests commonly carried out, the main one being the splitter deflection test.

Exploitation

Double Diffuser

Over the past two year these rules have been exploited by teams. Firstly the interpretation of holes in the floor and continuous surfaces. This lead to the openings that allowed double diffuser. Effectively the step formed two separate, but individually continuous surfaces, allowing airflow to pass up above the step plane into the upper deck of the diffuser. This rule has been clarified for this year and a single continuous surface must be formed under the floor.
Additionally the flexibility of the splitter has been brought into question, teams were believed to be flexing the splitter upwards, new more stringent tests were introduced in 2010 to stop this.



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Red Bull – Preseason front wing update

20110318-094109.jpg

In the last pre-season test at Barcelona, Red Bull introduced their updated front wing. Like the rest of the car, this is an evolution of what has gone before. Albeit based on the complex late-2010 set up, with 3-4 elements in differing areas across the wings span. It’s the endplate and cascade that have changed the most. While the flaps take some inspiration from Renaults early 2010 shape.

Firstly the shape of the main plane remains the largely the same, While the 2 flaps also retain their extra slot on the outermost span. This creates a four element wing nearest the endplate, this section gains a gurney to help keep flow attached. Meanwhile the inboard ends of the flaps follows Renaults idea from 2010, as they are feathered. This is visible by the space created in between the wing tips, Looking at the set up intuitively, the flaps remain loaded, but their tip vortex would be broken up into two smaller less powerful trails. Which still creates downforce, but may be less disruptive to the flow along the centre of the car.

20110318-094124.jpg

The cascade is slightly revised, again with the two conjoined winglets. Now the larger outboard winglet is curved near the join with the endplate, creating a deeper angle of attack and correspondingly a larger vortex spilling of the wingtip to direct airflow around the tyre.

20110318-094133.jpg

Mounting the new cascade is a revised endplate vane, Red Bull merge this organically into the rest of the outboard wing shape, but in principle this is the same as the vanedendplate-less set up of most other teams. The vane is slightly more outboard creating a wider cascade, probably for both more downforce potential and also to move the aforementioned vortex further outboard.



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Mercedes W02 preseason side pod & exhaust update

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After a slow start to the 2011 campaign Mercedes GP brought along the long expected changes to the W02 at the last Barcelona test. We have already covered the front wing (http://scarbsf1.wordpress.com/2011/03/11/mercedes-w02-new-front-wing-analysis/). But more crucially was the revised sidepod and exhaust package. Mercedes have gone their own way with the design of the W02, with its short wheelbase set up and the resultingly bulbous mid section. Contrary to my expectations the new sidepodexhaust package was not as unconventional as expected. Which still leaves some questions over some design choices on the car or the permanence of the solution shown in Barcelona.

20110318-094610.jpg

Firstly the new sidepods are formed of a completely new moulding, common to several other teams the sidepod bodywork is one piece and is not formed by add-on sections to the monocoque. Even though the general shape appears the same as the launch format, the overhead view shows the sidepod inlets are angled inboard slightly. Although the bigger visual change is the exhaust and cooling arrangement. Uniquely the exhausts are sited halfway along the sidepods, exiting where the sidepod is nearly at its widest and starts to taper in to the coke bottle shape. Unlike Red Bull and Ferrari Mercedes have not extended the exhaust towards the diffuser, instead the exhaust blows over a long length of open floor. A small vane redirects the flow inboard of the rear wheels and into a coved section that sends the exhaust flow under the diffuser to be more effective at creating downforce. To keep the bodywork safe from its close proximity the exhaust pipes numerous grilles are moulded into the sidepod. The rearmost of these are outside the exclusion zone for cooling outlets, but the larger removable grille appears to be at odds with the bodywork rules. Perhaps the low exhaust position (below the 100mm above the reference plane) allows the grille to be regarded as the opening for the exhaust. Equally these could have been precautionary fitments for overheating (which blighted the cars earlier tests) and might removed for the Australian race.
Having the exhaust so far forward does not make the exhaust act like Renaults Front-Exit-Exhaust, nor like Red Bulls ducted set up. The exhaust gas will lose energy as its merges with the freestream airflow before it reaches the diffuser. Its exactly this energy that teams want to exploit to drive more flow through the diffuser for more downforce. So why is the set up a less efficient solution? Potentially there are several reasons, last year Mercedes struggled with overheating bodywork, unable to get enough supply of the permitted Glass Ceramic Composite (GCC) material used to protect the phenolic composite of the cars floor and bodywork. When they ran their blown floor, the heat, simply melted and warped the bodywork. Its unlikely supply of the material is still an issue, but keeping the bodywork cool and the nature of the exhausts might be the problem.

All three Mercedes teams (McLaren, Mercedes GP and Force India) all had issues with sensitivity of the car when run with EBDs in 2010. McLaren found the cars balance changed significantly on and off throttle, while Mercedes found that the exhaust plume would touch differing parts of the bodywork in different sessions and even differed between cars. This suggests that the exhaust plume was less than predictable. Where-as CFD and wind tunnel tests use a simulation of the exhaust blowing, perhaps the knowledge of what the exhaust flow is actually like is missing. Strangely this seems to be a very Mercedes engine specific problem. Being too aggressive with the exhaust blowing and too specific with the heat shielding makes the car throttle-sensitive and prone to overheating bodywork. McLaren have more problems with their EBDs in pre-season testing and Force India have yet to truly shine, with an otherwise good looking design. If this is the case, then the teams either have to lose potential downforce by having to use a less aggressive EBD solution or suffer the sensitivity problem. Its hard to be clear how easy an unpredictable exhaust plume might be to solve, its not likely to be a solution teams and engine suppliers have had to look at before.

20110318-094617.jpg

Elsewhere on the sidepods the cars pod vanes have been enlarged from the truncated versions seen in the cars early tests. Why the team would be run stunted versions of long standing designs is again part of the confusion around the W02 debut. The pod vane features an unusual outwards bulged lower section. This mimics the shape of the short launch spec vane. I presume this is mated to the sidepods undercut to feed more flow around the sidepod and over the diffuser. Along with the new undercut the car sports new serrated bargeboards and the complex shaped under nose vanes from late last year have been revised with the more common nose cone mounted vanes.

One last unsolved conundrum is the side impact protection on the sidepods. Normally teams pass the side impact tests with two pairs of crash beams, one upper pair above the sidepod inlet and a lower pair in line with the floor. Each of these pairs are formed of one larger carbon beam and a smaller one to spread the load over a wider area of the chassis. Rules demand these parts are not exposed to the exterior airflow and must be covered by bodywork. These structures are quite heavy and unavoidably raise the cars Centre of Gravity (CofG). This years car sports something appearing very much like a side impact structure passing horizontally across the middle of the sidepod inlet. This would be beneficial as the weight is that much lower down and better for a low CofG, a high CofG was a problem that afflicted the 2010 W02. Meanwhile at floor level the structure is unusually slim, which is better for aerodynamics.
But this mid placed structure appears to be in contravention of the rules as its exposed to the airflow. The FIA have started to be stricter with teams interpretation of these structures, so its hard to understand why this set up has been accepted. Possibly the structure is covered by vestigial bodywork to bypass the rules, but this detail did again promote some of my ideas that the sidepods were to be more unconventional. If allowed this year, we can expect the FIA to stamp out this set up for future years. Of course teams cannot copy this, as crash structures are homologated for the year, and cannot be changed.



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McLaren preseason rear end update

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McLarens pre season has been thwarted by unreliability and apparently aerodynamic problems. The team have run a succession of exhaust designs (at least 4 so far) and time has been spent mapping the cars aerodynamics with sensor arraysflowviz. While the exhaust solution has yet to be finalised (I have a forthcoming post on this), The last days of the Barcelona test allowed the team to introduce some new parts around the back of the car and a new front wing.

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Their new rear wing sports vanes along its lower edge. These are legal as they sit in a small 5cm loophole zone in the bodywork regulations. This area has been exploited before by Red Bull on the RB5 and subsequently Toyota and Williams in 2009. Sauber also have much smaller solution on their current car. Having bodywork in this area effectively extends the diffuser sidewalls by some 30cm, which helps maximise the expansion ratio of the diffuser for more downforce. Such is the shape of the flow out of the diffuser, the bodywork needs to be vaned to allow the flow to expand. McLaren have formed four vanes into the allowable area. For the test, the rear-pointing exhausts were lined up with these vanes, thus the exhaust flow (red) will be routed by these vanes, accelerating flow inside the diffuser for even more downforce.

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McLarens problems also delayed the testing of their DRS (Drag Reduction System) adjustable rear wing. To feed the hydraulics to the actuator mounted inside the middle of the rear wing, the team have routed a non-structural pylon up from the gearbox to the wing. This houses the hydraulic cables & sensor wiring and does little to support the upper rear wing.

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With the weather warming a little during the relatively cold Spanish tests, the team were able to reduce the size of the engine hot air outlet for the last test. In the middle of this outlet is the oval gearbox oil hydraulic cooler outlet. Leaving the rest of the outlet for general sidepod cooling



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