Analysis: Abu Dhabi Test – 2012 Exhausts

Image via Williams F1

Last weeks Young Driver Test was the first chance for teams to try exhausts systems designed to the revised 2012 rules. Next year teams will have to place the exhaust exits in a specific region of the car, with further restrictions on the pipes shape and angle. These changes have been introduced to ban the blowing of the diffuser for aerodynamic gain. While I have detailed these rules previously (http://scarbsf1.wordpress.com/2011/10/26/2012-exhaust-position-and-blown-effects/), we can start to look at what the teams have been doing in Abu Dhabi.

Three teams brought revised exhausts, most notably Williams who ran their exhaust in all three days of the test, while Mercedes did less running with their interim set up and Ferrari tried a non legal exhaust on just one of the testing days.

Williams

IR cameras point upwards towards the wing and pods on the wing house sensors (Image via Williams F1)

Shunning any running with an Exhaust Blown Diffuser (EBD), Williams ran in Abu Dhabi with an exhaust positioned within the correct area and orientation as demanded by the 2012 rules. Their exhaust is a simple interpretation of the new rules, with the exhaust placed close to the cars centreline and as rearwards as possible. Most interestingly the exhaust is tipped up at the maximum 30-degree angle. This positioning suggests the team are trying to blow the centre of the underside of the rear wing. While I have proposed more radical solutions in my previous article, this does show that teams are to look at blown rear wing effects, as opposed to purely aero neutral exhaust positions. Exiting the exhaust pipe at great speed and temperature, the exhaust plume will hit the underside of the rear wing. This would have the effect of speeding up the airflow under the wing decreasing pressure and creating more downforce.

Williams Exhaust is low and rearward within the legality zone (yellow) and points upwards at a max of 30-degrees

However this effect is more complex than a simple jet of gas hitting the rear wing. Gordon McCabe’s Blog (http://mccabism.blogspot.com/2011/10/exhaust-blown-diffusers-in-2012.html) highlighted some research by Prof. K. Kontis & F. L. Parra from the University of Manchester on the effect of exhaust gasses on an F1 car. They found the exhaust plume passing at an angle out into the airflow created its own drag and moreover was bent backwards by the airflow at greater speeds. When this theory is applied to the Williams set up of a steeply inclined exhaust pointed towards the wing suggests some very interesting effects come into play. Firstly at lower speed the exhaust plume (jet) will be far stronger than the flow over the car. Thus this jet passes upwards through the crossflow over the car, will reach the rear wing to create more downforce.

Jet in Crossflow - low speed: unimpeded the exhaust plume blows the rear wing

At lower speeds the jet obstructing the crossflow will create drag and there will be drag induced by the greater rear wing mass flow, but being at lower speeds this drag will not be detrimental to aero performance. Then at higher speeds when the crossflow over the car has more energy the exhaust jet will start to bend backwards. Most likely moving the jet away from blowing the wings under surface. Thus the blown rear wing (BRW) effect will reduce, the car will lose some downforce and the drag induced by the blown effect will also reduce. Thus at higher speeds the car will shed drag, further boosting top speed.

Jet in Crossflow: High Speed - the faster airflow over the car bends the exhaust plume downwards away from the wing

Williams Abu Dhabi Test exhaust is not a clear sign that they will have this exact positioning for 2012, but the test will have proven the blown effect and just as importantly provided data on the heat passed over the rear wing. It was clear that the rear wing was set up with numerous sensors for vibration, heat and pressure measurement. Many of these sensors were within the rear wing flap itself, the shear number of sensors run on the wing required two aerodynamic pods mounted to the rear wing endplate to house the wiring to send the data back to the onboard data-logger. Additionally Williams ran several different kind s of thermal cameras, mounted to the rear crash structure and pointed upwards looking at the underside of the rear wing. This would not only provide actual temperature measurement, but also highlight which areas are being blown by the exhaust, somewhat like a thermal flow-viz test.

Mercedes

Another one of the teams late to the blown diffuser in 2011 and in particular blowing the outer section of floor by the rear wheel, Mercedes also tried a non-EBD set up in Abu Dhabi. According to earlier comments by Ross Brawn on autosport.com (http://www.autosport.com/news/report.php/id/96276), the Mercedes test exhaust was not a definitive 2012 set up “”The car will be testing next week with our first interpretation of what the regulation will be.”, but merely a revised exit location to remove the exhausts effect from the rear ends aerodynamics, “This is compromised because we’re fitting it around the existing car, but we’re removing the effect of the blown exhaust to see how the car will work without that.”

The set up that Mercedes tested with was similar to Williams with the exhaust outlet focussed towards the innerrear of the regulatory box it needs to sit within. Flanked by bodywork the exhaust did not appear to be as steeply inclined as the Williams set up. Reinforcing Brawns comments about removing the blown effect.

Pictures in F1talks.pl gallery http://www.f1talks.pl/2011/11/17/ostatni-dzien-testow/

Ferrari

Like Mercedes Ferrari run an alternative exhaust on the last day of the test. However unlike these previously two teams they did not fit a 2012 spec exhaust. Instead the cars left-hand exhaust was routed dramatically sideways to exit ahead of the rear tyre. This set up would not be legal either in 2011 or 2012, but was probably a simple to completely remove the blown effect from the rear of the car. With the right hand exhaust apparently in its normal EBD set up, the team would be able to measure the difference in pressure left to right to access the effect the exhaust is having. While a large part of development for 2012 will be aimed at getting the exhaust to do some useful work elsewhere eon the car, such as a blown Rear Wing (BRW), the team salsa need to get the diffuser and rear brake ducts working without the artificially accelerated airflow blowing over the from the exhaust. As the test exhaust does not fit into the current regulations this test would be the one place where they could do this, with permission to run such an exhaust being unlikely for a Friday practice session. So although preparation is underway for their exhaust development, Ferraris plan for their 2012 remains hidden.

Ferrari: A Chamber has been added to the Exhaust system (yellow)

One area of Ferraris exhaust development that has recently been exposed is the exhaust chamber. These devices have been rumoured for many months. Most of the rumours attributed to Mercedes engined teams, although no evidence has appeared of the system on any of their three teams cars. As reported by Giorgio Piola at the Abu Dhabi race, Ferrari had this system in place for the Grand Prix and the system remained fitted for at least part of the test. What at first appears to be another exhaust outlet joined to the secondary exhaust pipe, is in fact a closed ended pipe. This picture of the exhaust removed from the car (http://www.f1talks.pl/2011/11/17/ostatni-dzien-testow/?pid=7210 via F1talks.plSutton Images), shows the large extension, which acts as a pressure accumulator when the exhaust is blowing. Then when the driver is off the throttle the pressure built up in the chamber is release, which smoothes the blown diffuser effect between full and partclosed throttle.

When on the throttle the chamber is pressurised along with the exhaust system

..

When off the throttle the chamber maintains some exhaust flow

Similar systems were common on Japanese 2-stroke motorbikes in the eighties, albeit placed on the inlet side of the engine (often termed ‘boost bottles’), Fords WRC car also featured a chamber on the inlet side for similar effect.

This system works on the backpressure created within the exhaust. It’s worth noting Ferrari have recently switched to the nozzle type exhaust outlets, these being narrower in cross section to that of the main exhaust pipe. Most probably these nozzles work to increase backpressure to smooth the exhaust plume at different throttle openings. Just as interesting is the switch of the Mercedes powered teams to nozzle type exits mid season, suggesting the exhaust chamber rumours may be true. It would be logical to assume that the back pressure created within the exhaust both by the nozzles and the chamber would affect top end power. But any time loss being made up by the less senstive aerodynamics.

In some respects this exhaust chamber is similar to what appeared to be a one-way exhaust valve fitted at several GPs this year. The belief being that the exhaust valve allowed the exhaust to suck in air when the driver was off the throttle, to maintain exhaust flow to the diffuser. This being a mechanical alternative to the off throttle mappings (Hot BlownCold Blown), which were to be banned mid season. There appears to be a move to again enforce engine mapping restrictions for 2012, so the teams will need to find ways to smooth the exhaust plume over the bodywork. But this one-way exhaust valve will be expressly banned under the 2012 Exhaust Regs. So the exhaust chamber solution appears to be a design what will become present on the many cars exploiting blown exhaust effects in 2012.

Analysis: Ferraris Front Wing Flutter

In free practice for the Indian GP, we saw a violent fluttering of Felipe Massa’s front wing. This is a higher frequency movement than the flex we commonly see on front wings – in fact, the movement is enough to cause the endplates to hit the ground, sending up showers of sparks. Bearing in mind that the wing is around 75mm off the ground when the car is at rest, we can appreciate the amount of movement that’s occurring here.
This movement is not an aero benefit in itself, but may be symptomatic of other flexibility in the wing.
Ferrari Flexi Wings 2011 Indian Grand Prix FP1 by Mattzel89

This clip shows the Ferrari crest the hill before braking into a turn (4s into the clip). As the car crests the hill at high speed with DRS open, it’s clear that the wing is bowed from the aero load. It’s possible to see the side spans of the wing bend down from the central section. At this point there is some vibration in the wing, but not an excessive amount. As the car starts to go down hill (DRS still open) and passes a shadow across the track, the wing starts a rocking motion (5s into the clip). This rocking soon increases in violence until Massa closes the DRS and starts to brake as usual for the corner (at 9s), so this episode only lasts three seconds. I counted around 20 movements of each endplate, which increase to the point where the endplates’ skid blocks strike the ground.
The cause may be explained as follows: the wing is bowed at speed, but as the car crests the hill the wing is unloaded slightly. Then, as the car starts to move down hill, that load would reverse and the wing (which was already vibrating) is sent into a rocking motion. One endplate moves down, while the centre section and wing mounting pylons appear to be rigidly fixed to the car and are not moving. The load passing from the endplate must have been transferred across the central spar of the wing to the other endplate, which now drops. This movement resonates in a wave from one side of the wing to the other, increasing in frequency and amplitude until the wing actually hits the ground.
I can’t explain why closing the DRS and braking calmed this resonance so quickly, but the wing rapidly returns to the low-amplitude, high-frequency vibration seen elsewhere on track.
Also, I’m no expert on composites but my limited knowledge does suggest that carbon fibre structures are relatively well damped (compared to, say, a metal structure), the rebound effect of flex being relatively well damped and not prone to oscillating.
Ferrari introduced the new front wing in Korea. Alonso ran the wing as it was clear that it displayed the accepted level of flex as used by many other teams. The wing is legal as it meets the more stringent FIA 2010 deflection test. Last year Red Bull set a precedent when its wing, which openly appeared to bow downwards at speed, passed the tests and was declared legal, even when the test loads were increased mid-season.
This bowing effect – where the tips of the wing move downwards at speed – is commonly used as the front wing then sits closer to the ground and can generate more downforce. Despite a lot of theories about mechanisms or heat being responsible for the flex, the answer is much simpler: it is down to the way you want the wing to work i.e. the tips to bend down without the wing twisting and thereby reducing the wing’s angle of attack. This is all done with the lay-up of the composites – I’m told it is a “nightmare“ and have heard of composites technicians spending weeks trying different lay-ups to get this effect, but once worked out it is very effective.
Of course F1′s knowledge of carbon structures has been used to create very stiff parts, but now that we are starting to allow controlled flex, we will start to see resonance becoming an issue. There is a new field of knowledge to be understood and controlled.
It seems the wing was tried again in FP3 and the FIA has taken an interest in the wing. The wing was removed and one would assume that it will not be raced for fear of mechanical failure or a post-race ban, although Ferrari’s Friday press release may suggest that the wing is a development item not planned for use in the race, but as part of the 2012 programme. Pat Fry: “We continued with the now usual parallel programmes: on the one hand looking for the best set-up for the car at this circuit and on the other, working to get a greater understanding of the latest aerodynamic updates, with the new car project in mind.”
We have seen extreme movement of front wings before in super slow motion, such as wing tips fluttering, wings swaying sideways on their mounting pylons and endplate devices flapping. All of these movements, although highly visible, have been accepted by the FIA because the tests have been passed. All of which is to the detriment of the overriding regulation that bodywork should be rigid and immovable.

Thanks to Andrew Biddle (andrewbid@gmail.com) for his assistance as Copy Editor

Front Anti Roll Bar Solutions

An excellent Sutton Images picture seen on F1Talks.pl, taken through the aperture on the front of the McLaren has given us a rare chance to see the set up of the front suspension.

(http://www.f1talks.pl/2011/08/25/czwartek-na-spa/?pid=4590).

Typically most teams follow the same set up for the front suspension in terms of the placement of the rockers, torsion bars, dampers anti roll bars and heave elements. As unlike with rear suspension, the raised front end almost dictates a pushrod set up in order to the get the correct installation angle of the pushrod. However the McLaren antiroll bar shows there is some variation in comparison to the norm and also highlights Ferraris similar thinking in this area.

In comparison to my more recent posts, this is not a breakthrough in design, simply a chance to see the teams playing with packaging to achieve similar aims.

Typical front suspension

As an overview of the conventional of the rocker assembly in the attached diagram shows the rockers are operated by the pushrod, a lever formed by the rocker operates each of the suspension elements. Compressing the heave spring and wheel dampers, extending the inerter and twisting the torsion bars.

A typical "U" shaped ARB: Arms connect the torsion bar to the rockers via drop links

Typically teams use a “U” shape anti roll bar (ARB). In this set up the antiroll bar is connected to the rocker via drop links, and then each arm twists the torsion bar when the car is in roll. When the car is in heave (car going up and down, no roll) the ARB simply rotates in its mounts and adds no stiffness to the suspension. Different torsion bars in the anti roll bar create different roll stiffness rates for the suspension. Teams will either switch the entire ARB assembly for a different rate ARB. Red Bull have engineered their ARB for the torsion bar to be removed transversely through the side of the monocoque, in a similar fashion to removing the normal torsion bars.
However McLaren and Ferrari have gone a slightly different route.

Mclarens ARB

McLarens ARB is formed of two blades joined by a drop link

In McLarens case their ARB is a simple blade type arrangement. These blades are splined to each rocker the blades are joined at their ends by bearings and a drop link.

In roll, the blades react against each to create roll stiffness

When in roll the rockers rotate in the same direction, one blade goes down and the other goes up, the stiff drop link transfers these opposing forces and the blades flex. These opposing forces add stiffness to the front suspension in roll.

In heave, the blades move together

In heave the rockers rotate in different directions, both blades move down and the increasing gap between their ends is taken up by the drop link. So the blades do not flex and do not contribute to heave stiffness.
Different thickness blades create different roll stiffness; they must be removed from the rockers and replaced to achieve this.

Ferraris ARB

Ferraris ARB uses two blades joined by an elegant arched guide

Ferrari have used this solution at least since the late nineties, the idea has been seen on older Minardis too. I suspect the idea was taken to Minardi by Gustav Brunner, who may also be the creator of this elegant solution.
Similar to McLaren the roll stiffness is provided by blades splined to the rockers. But the connecting mechanism is instead a single bearing sliding inside an arched guide. Just as with McLaren ARB, when in roll the two ends push against each other to create the reaction force to prevent roll. When in heave the bearing slides through the arc of the guide and no force is passed into the suspension.

Summary
I don’t believe either of these solutions has a compliance benefit over the other. The McLarenFerrari systems may be take up a little less space inside the nose and may weigh a little less. But both will be a little more complex when changing the roll stiffness.

Assemblies

Ferrari: New Front Wing Analysis (summary)

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

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

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

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

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

Ferrari: Silverstone Upgrade

Silverstone brought Ferrari’s major mid-season upgrade to the F150, which was effectively a complete new rear end package. Their upgrade comprised of new exhausts, rear suspension, engine cover, diffuser and rear wing. While the changing rules and weather conditions made it hard to judge if their win was a result of these changes, it was clear that the car had found new pace in fast turns. This in its self is a sign of improved downforce, one of the aims of the upgrade.
Ferrari have been open throughout the year in stating they lack downforce and struggle to get heat into the tyres. The former issue hurts pace on faster turns, while the latter has the combined effect of lost pace on harder tyres and poor single lap qualifying pace.
Again Ferrari s honesty in saying the car was not aggressive or innovative, was clear from its launch. Red Bull, McLaren and other teams tried new ideas. Not all these created the package to beat Ferrari, but Red Bull and McLaren were well ahead of Ferrari in the aero race early in the season.
It seems Ferrari chose to make the car as soft on its rear tyres as possible; as the original expectation was that the Pirelli rear tyres would degrade more rapidly. Certainly Ferrari have been easy on their tyres, but the flipside of this characteristic is that the car can struggle to get heat into the tyres. This is why their pace at Barcelona on the hard tyre was so poor and why they struggle to get the pace on a single flying lap qualifying run.

So with this Silverstone package these areas were addressed and the initial signs are the car has improved.


Firstly the rear wing was all new, aerodynamically, structurally and with its DRS operation. Their new rear wing no longer used a central pylon to support the upper wing and house the DRS actuator. This clears up the underside of the wing from obstructions; this was probably not to reduce the minimal amount of drag created by the support, but more to removes its turbulence from the underside of the wing. Perhaps this will aid the reattachment of the air flow when the DRS closes the flap. Instead the DRS actuator is inside a small pod above the wing, where it will less affect the airflow. Cabling and hydraulic lines to the actuator route inside the wing and endplates. As the pylon has been removed there remains a small section of it on the crash structure ahead of the beam wing (highlighted).


Ferrari have been playing with their rear suspension layout for several races. Visibly the main change appears to be where the upper wishbone meets the upright. This has been moved away from the wheel, by making extending the position of the pickup point on the on the upright. This creates a shorter upper wishbone. The effect of this would be more camber change and lateral scrub as the suspension is compressed. In simple terms as the cargoes down on its suspension the wheel will tilt inwards more and slide across the track surface towards the centre of the car. Both these actions move the tyre about a lot more and help create heat in the tyre. This is how Ferrari have been able to get their tyres into their operating temperature window.

The team ran a new engine cover, with the tail of the sidepods formed in a tighter shape, with some of the cooling accommodated by louvers in the tail of the coke bottle shape.


Lastly the floor and exhaust were subtly changed, with the exhaust pipe shape being altered and the cut away sections of floor being a different profile. Unlike Red Bull, Ferrari have not gone very far in aiming exhaust flow under the car. However they have still gone further than the other teams running the outer blown diffuser. The floor in between the tyre and the diffuser is no longer carbon fibre. But instead a plate of titanium, pictures show this flat metal floor is fully exposed and carefully curved to invite some flow to pass under it. Changes in this area no doubt were made with the 10% engine mapping rule in mind, but also as the diffuser itself used a new geometry.
The next series of races with fast turns and harder compound tyres will prove if Ferrari have reversed their cars characteristics and can take the fight to Red Bull for the remaining ten races

Ferrari: Rear Dual Rate Anti Roll Bar

Ferrari rear suspension package: copyright- Liubomir Asenov

When comparing the fortunes of the three leading teams, one stand out feature has been Ferraris kindness to its tyres and its great traction. Although both these traits are hugely complex and achieved by a variety of factors, we have been able to identify a solution in Ferraris rear suspension that may be providing some of this mechanical grip. As one of the few leading teams to retain pushrod suspension in 2011, Ferrari have at least given a chance to see the clever mechanical set up at the of the car. We have already discussed the relative merits of pushrod Vs Pullrod and looked at the rear end packaging of the Ferrari (see the links at the end of this article). But what this detailed shot by Liubomir Asenov shows us, is the clever arrangement of the rear Anti Roll Bar (ARB). Ferrari have developed sprung drop links to create a dual rate ARB, which gives the team the advantage of soft roll control for low speed grip and stiff roll rates for high speed aero grip.

A typical Anti Roll Bar. copyright: Craig Scarborough

An Anti Roll Bar (ARB) is a spring that helps the chassis resist roll when cornering. Typically in a racecar this is a relatively simple “U” shaped arrangement, with levers acting on a torsion bar. Drop links lead from the rocker to the ARB. When the car rolls one rocker goes down and the other goes up. The links twist the ARB, which in turn provides the spring effect to resist the cars roll. A stiff rear ARB will be good for maintaining the underfloors attitude to the track, in order for the diffuser to work at its best. However at lower speed, a softer ARB will aid grip by allowing each tyre to maximise its contact with the track. Clearly some tracks will favour aero over mechanical grip, but laptime gains be found if the car can improve both aero and mechanical grip.

What Ferrari has done is to replace the drop links that lead from the suspension rocker to the ARB levers with small coil springs. Now when the car rolls, the softer coil spring compress first, these provide a soft initial ARB rate, which provides good mechanical grip. Then as their movement is taken up, the coil springs act like solid links to the ARB and the stiffer main ARB provides the tighter roll control to aid the underbodies aerodynamics.

This solution appears to be unique to Ferrari in F1, but is a known solution in other race series.
Andrew Thorby (Designer for Panoz, Lister, McLaren MP4-12c GT3) pointed out to me that Lola is known to have used this solution in some of their cars, using either coil springs or belleville springs. He also pointed out that although small; these Ferrari coils springs are mounted quite high up, over what is already a relatively high suspension package, thus upsetting the cars Centre of Gravity slightly. Other teams achieve similar variable rate ARBs with the geometry of the drop links and levers. Whether pushrod or Pullrod, any team could conceivably employ these spring links to provide this variable roll rate.

Analysis of Ferraris rear end packaging
http://scarbsf1.wordpress.com/2011/03/23/ferrari-rear-end-exhaust-and-drs-mechanism/

Analysis of pushrod versus pullrod
http://scarbsf1.wordpress.com/2010/10/10/red-bull-pull-rod-suspension-what-is-looks-like-how-it-benefits-aerodynamics/

Ferrari: Spanish Rear Wing Extension

In Free Practice for the Spanish this weekend, Ferrari caused a small technical controversy when they ran a new rear wing. This new wing appeared to have large extension to the rear flap. After the days sessions were complete Charlie Whiting from the FIA spoke to Ferrari about its legality.

This 30mm extension was fitted the Ferrari 150 in Spain

We can see the wings long extension is not in fact a gurney flap as it is not an “L” shape. Instead the extension forms a continuation of the flaps shape. This makes the wing some 30mm longer than allowed within normal interpretations of the regulations. Clearly this much additional surface area will create more downforce. Beneficially this tall extension also retains the DRS pivot axis in its normal location, such that the when the larger flap is moved by the DRS the flap flattens out much more than with a conventional large flap (See http://scarbsf1.wordpress.com/2011/05/20/drs-optical-illusion-why-some-wings-appear-to-open-wider/).

How could this be achieved legally?

Ferraris Slot Gap Separator

 3.10.3 In order to ensure that the individual profiles and the relationship between these two sections can only
change whilst the car is in motion in accordance with Article 3.18, they must be bridged by means of pairs
of rigid impervious supports arranged such that no part of the trailing edge of the forward section may be
more than 200mm laterally from a pair of supports. These pairs of supports must :
– be located no more than 355mm from the car centre line ;
– fully enclose each complete sections such that their inner profiles match that of each section. With
the exception of minimal local changes where the two sections are adjacent to each other, their
outer profiles must be offset from the inner profiles by between 8mm and 30mm and may not
incorporate any radius smaller than 10mm (‘gurney’ type trim tabs may however be fitted between
the supports) ;
– be aligned as a pair so as to provide a bearing across their full thickness and along a profile length
of at least 10mm when the distance between the two sections is at its closest position ;
– not be recessed into the wing profiles (where a recess is defined as a reduction in section at a rate
greater than 45° with respect to a lateral axis) ;
– be arranged so that any curvature occurs only in a horizontal plane ;
– be between 2mm and 5mm thick ;
– be rigidly fixed to their respective sections ;
– be constructed from a material with modulus greater than 50GPa.

Ferrari have sandwiched and split the separators to form the extension

What I believe Ferrari have done is the sandwich the two separators together in the centre of the wing, then split them at the “V” cut out in the middle of the wings trailing edge. Each separator then runs along the trailing edge of the flap, creating the extension. As the extensions can be 30mm deep they can be 10mm more than the 20mm allowed for Gurneys.
It could beat the rules as each separator runs along the trailing edge, no part of the wing is 200mm laterally from a support. The change from the longitudinal centre separator to the trailing edge could meet the horizontal curvature requirements.

Each Separator also forms the 30mm extension

Overnight I heard from Spain is that the wing will be allowed for this race, but a clarification from the FIA ill ban this interpretation for future races.  However this morning conflicting stories are emerging.  Andrew Benson from the BBC reports “Ferrari have been told they cannot run their “clever” new rear wing design – it exploited a loophole in the regs to do with overall height” (@andrewbensonf1).

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Ferrari rear end – Exhaust and DRS Mechanism

A ScarbsF1 follower in the Melbourne pit lane sent me these exclusive pics. We can see the Ferrari stripped in the garage. There’s a huge amount of detail to take, but the key things are the exhaust routing for the EBD, the rear suspension and Rear Wing mechanism.

The exhaust loops forwards before turning back on itself to route towards the diffuser. This set up is used as it keep the exhaust well forwards within the sidepod, which helps to keep the sidepods tight and slim. We cant see the final section of floor, this might need to be removed in order to take the floor off.

Ferrari retained the pushrod rear suspension set up for the F150. To keep it competitive in aero packaging in comparison to the recently favoured pullrod, they have pushed the entire rocker and damper assembly to the front of the gearbox. In doing so they have placed the rockers nearly flat with their pivots pointing down. This keeps the assembly in the aerodynamic shadow of the engine and airbox, so effectively they don’t add any volume to the rear ends aerodynamics.

Lastly the “Drag Reduction System” mechanism can be seen sticking out of the gearbox. This is a hydraulic system and needs to be powerful in order to move the rear wing flap at quickly at speed. As both the flap will be heavily loaded by airflow and designers want the switch from closed to open to be in a matter of milliseconds.



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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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Ferrari F150 – final pre-season update analysis

For the final test at Barcelona, Ferrari brought the long awaited revisions to the F150 (although the cars name has frequently changed, I’ll continue to use this title). This consisted of a revised wings, new sidepods and new exhausts. It was Ferraris assertion at its launch that the car would have evolved aero and specifically different exhausts before the first race. So despite some people suggesting the changes are copying their rivals, it’s more likely that different teams have converged on the same ideas.

The front wing pylons have been lengthened to form turning vanes

At the front the main changes are to the front wing and its supporting pylons. These pylons have been extended in a similar manner to Renaults ideas from 2009-2010. Since 2009 the rules on vanes and bargeboards around the front of the car have been severely restricted. The rules mandate a limit on the cross sectional area for the front wing mounts, Ferrari have therefore extended their wing mounts, but also narrowed them. Thus meeting the rules and still providing the car with some aero advantage.

3.7.2 Any horizontal section taken through bodywork located forward of a point lying 450mm forward of the front wheel centre line, less than 250mm from the car centre line, and between 125mm and 200mm above the reference plane, may only contain two closed symmetrical sections with a maximum total area of 5000mm2. The thickness of each section may not exceed 25mm when measured perpendicular to the car centre line.

A shapelier endplate has been added to the cascade

Details of the front wing have also changed, in particular the endplates, these now feature a more sculpted vane on the footplate. As well as the endplate fro the main front wing, the inner endplate for the small cascade mounted to it is also now shapelier. The small endplate now having a distinctly flared shape, aimed at redirecting flow inside the front wing.

New sidepod inlets and a blown diffuser are the main changes to the F150

Along the middle section of car, Ferrari have produced a new sidepod, initially similar to the launch specification. But the main radiator inlet is now reshaped, being much more of a “U” shape and smaller with it. The sidepod inlet retains the distinctive protruding upper lip. I was told by Nick Tombasis that this was an aero feature and not a structural one (i.e. side impact crash protection). Curiously this lip features a removable panel to allow for cooling. Being so far forward of the radiators its hard to understand how heated radiator flow could be ducted into the small exit, or perhaps some electronics of KERS components are sited within this hollow section.

Further back along the sidepods, the new exhaust system is routed along the floor and into an open section of floor in the outboard 5cm section of diffuser. This is the same solution as Red Bull has come up with, as already explained this was an obvious area in the 2011 rules for exploitation, as I even proposed this location in my pre-season trends and solutions article. Ferrari route the flattened exhaust inside heat shielding along the floor. The blowing effect of the exhaust passes under the floor for a more effective method of blowing the diffuser. Ferrari wanted to produce the exhaust in glass ceramic composite (such as Pyrosic), but this request was denied by Charlie whiting who clarified the exhaust must be made of materials on the permitted materials list. Such composites, while allowed to be used in some exceptions, are not allowed to be the actual material of the exhaust pipe.

Also the middle of the car gained revised wing mirror pods.  these appear to be split into upper and lower mouldings. Presumably to allow sensors or electronics to be fitted inside the pods during testing or free practice.

Lastly the rear wing has also been modified with a smaller flap. Several teams have switched their rear wing to smaller flaps, at first this is counter intuitive to the exploitation of the Drag reduction system (DRS) also termed the adjustable rear wing. As one would initially deduce that adjusting a larger flap would reduce drag by a greater amount. However, shallower flaps effectively flatten out when the leading edge is moved 50mm from the trailing edge of the main plane (50mm is the maximum slot gap allowed for the DRS). Thus they produce very little load and therefore little drag.



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