2012: Exhaust Blown Diffusers are banned

This is an evolving story, I will update the post as more info becomes available

It has been reported in Pitpass.com that exhaust blown diffusers will be effectively banned in 2012. Currently exhaust outlet can be anywhere on the car, many teams aim the exhausts at parts of the diffuser to create greater downforce. Red Bull for example blow theirs under a 5cm opening in the floor, Renault blow theirs at the floors leading edge and FerrariMcLaren and many other teams blow theirs over the top of the diffuser.

An example of current exhaust location

Along with the hot overrun engine mappings, teams have been exploiting the exhaust gasses for aerodynamic gain. Something the FIA have been increasingly uncomfortable with. According to the BBC “From 2012, pipes will have to extend to between 330-350mm beyond the rear wheel centre line, will have to be in a space between the lower rear wing and top of the diffuser and will need to be circular in dimensions, with a vertical cut-off”. This is effectively at the trailing edge of the rear tyres. Although some careful placement might find a tiny aero gain, the massive benefit of the EBDs will be lost.

Following the Technical Working Group meeting this week, Autosport reports that the ban on blown ovverrun engine maps will go ahead from Silverstone, but a compromise on the location of 2012 exhausts has been reached.  Teams wil now be mandated to use periscope style exhausts as were the norm from 1998 until this year when low placed exhausts became the universal fitment.  It remains to be seen how the rules will enforce exhausts in this location.

For 2012 the exhaust must exit behind the rear tyre and between the diffuser and beam wing (yellow)

With the initial ban on how overrun engine mappings, Renault and red Bull stand to lose out the most. With the full EBD ban in 2012, it is again these teams with the most to lose as each of these teams blow beneath the floor. Teams such as Ferrari and McLaren who have committed to aggressive blowing the diffuser will also stand to lose from the ban.
Engine suppliers will have to work on ways to make the engines work with such long secondary exhaust pipes, teams will have to work out the packaging of the exhaust, blowing most likely near the cars centre line, which brings the exhausts close the hydraulics and gearbox. In this area blowing the underside of the beam wing could be exploited, or  blowing the gurney at the diffusers trailing edge will also be an attractive option.  Blowing outboard is unlikey to be attractive, as it create the longest exhaust routing and exposes a lot of floor to the heat radiating from the exhaust pipe. In both case the longer exhausts will obstruct airflow to the diffuser, forcing some compromises in packaging.
One benefit for fans will be the clear line of sight to the exhausts, allowing us once more to the flames on the overrun and when revving on the grid before the start.

Renault & Wiliams: Complex low drag wings for Canada

Both Williams and Renault had complex wings for the low drag demands of the Canadian GP. In Williams case the wing is shaped to create most downforce in its centre, leaving a much shallower span near the endplates. This design reduces the pressure difference where the wing meets the endplate. This reduces the vortices produced at the wing tip and hence drag. Although the Williams wing is fitted with DRS, low drag is still critical as DRS can only be used in the race in the situation where the car is less than 1s behind another at the DRS detection zone.

Renault meanwhile have twisted their rear profile to match the oncoming airflow. This is in fact an old wing already seen in 2010.

Williams: Endplate-less Front wing

Williams introduced a new concept of front wing for Canada. Working along similar geometry for the three wing elements, the endplate design has evolved to be formed totally by the wings main plane. In order to meet the rules of side profile surface area, the wing sports a vane that also mounts the cascade. While sealing the airflow beneath the wing, a function normally served by the endplate is formed by a small fence added below the main plane.

You can see with the cascade and under-fence removed, there is effectively no seperate endplate

With the cascade and under-fence removed you can see the line of the main plane (yellow) forms a continuous curve across its entire length, no separate parts form the end plate. You can also see the two flaps curve down to form the rest of the ‘endplate’ function.

An extra slot in the main plane near the outer tip, makes the a 4-element (3-slot yellow) set up

Lastly the wing continues to exploit a solution used by Williams all season. The wing is notionally a three element design, with a main plane and two flaps. However an extra slot is formed in the outer span of the main plane and this formed effectively a four element for more highly loaded outer section. You can see the depth and length of the wing in this outer is greater than the other sections of wing, so this area creates the highest amount of downforce.

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

Analysis of pushrod versus pullrod

Red Bull – Monaco floor analysis

Monaco is a unique venue, not just for the layout of the circuit, but also the pit lane facilities provided to the teams. With no space for a conventional paddock and pit building, the teams park their transporters away from the small pit garages. Thus parts have to be ferried in-between the trucks and the pit, as well as parts being stored in the upper floor of the pit facility. Luckily for F1s technical observers, this presents an opportunity to see parts not normally exhibited in front of fans. Just such an opportunity presented itself to Jean Baptiste (@jeanbaptiste76) who saw Mark Webbers floor being lifted up to the mezzanine, through the crowd he was able to a quick photo of the entire assembly. From a single picture we have been to gather a lot of info on the design of Red Bulls floor. We’ve confirmed where the exhaust blows, how the trailing edge forms a flap and exclusively how the starter motor hole is blown by ducts in the upper floor. There also a wealth of detail not normally visible, although not unique to Red bull, seeing this detail is a rare treat.

Firstly we can see that this is a floor that has been run on the car, evident by the burns and dirt generated to what would otherwise be pristine black and silver floor. I suspect this is a floor assembly used for free practice, as the floor ahead of the rear tyres still sports the tyre temperature sensors. These are not typically run from qualifying onwards.

We can also see that the floor is in one complete piece, which is unusual. Normally the front t-tray splitter section is removable. Perhaps with the front splitter being lighter this season, it no longer formed of a large piece of ballast, making having a one piece floor more convenient. Plus the new more stringent splitter deflection tests are probably easier overcome with a single structural assembly, rather than two assemblies bolted to the car. Plus we can see the front bargeboards are a permanent fitment to the floor, whilst the sidepod fins are unbolted from the floor and remain attached to the sidepod fronts.

Exhaust routing

Silver coating (zircotech) and gold film provide heat shielding

We’ve seen many pictures of the Red bull exhaust system, how it curls down to pass the exhaust along the floor towards the outer 5cm of floor aside the rear tyres. Obviously no exhausts are fitted to the floor, but the general heat protection within the engine bay appears a coating applied to the carbon floor (most likely Zircotech). Additional local heat protection is provided with separate heat shields and gold reflective sheet, under the exhaust area. The exhausts then run out of the engine bay and along the floor. Again reflective coating is used on the bare floor beneath.

The exhausts route along the floor and blow beneath the diffuser

We can then see the exhaust exits to the edge of the tyre decks 9the small section of floor between the tyre and diffuser. This area is extensively cut away and the edge of the floor is a metallic part which curls up to encourage the exhaust to pass beneath the floor and into the diffuser. We have seen from pre-season (http://scarbsf1.wordpress.com/2011/02/02/red-bull-rb7-open-fronted-exhaust-blown-diffuser/) that the exhaust curls up into the outer top half of the diffuser, further proven by the additional heat protective coating applied in this area. Recent pictures of the Ferrari being craned away in Spain, show that Ferrari do not shape the floor to encourage as exhaust flow to pass under the floor, McLaren are also more similar to Ferrari than Red bull in this regard. As of Monaco 2011, Red Bull were the only team to passing the exhaust flow under the outer edges of the floor towards the diffuser.

Trailing edge flap

On the diffusers trailing edge a flap aids downforce

Red Bull switched to a revised diffuser at the Chinese GP, this exploited a new treatment to the top trailing edge of the diffuser. Rather than a simple Gurney, the team formed a flap above the trailing edge in-between the rear wing endplates. This was not a new feature in F1, Toro Rosso launched their car with just such a flap and historically many cars have sported the detached gurneys of flaps. The Arrows cars in the 2000s sported just such devices. Completely legal, these simple aerofoil sections of bodywork, sit within the allowable area for bodywork at the rear of the car. Much like the gurney, these devices aim to use the high pressure air moving over the diffuser to create a low pressure region above the diffuser exit, to drive more flow out of the diffuser beneath. Effectively making the diffusers exit area larger than a simple exit.

Blown starter hole

Two inlets lead to ducts (yellow) that feed the Starter Motor Hole with airflow

What’s most interesting from Jean Baptistes picture are the two ducts set into the floor ahead of the diffuser. Looking closer we can see these two inlets, lead to ducts that pass inside the engine bay and either side of the starter motor tube. The starter motor hole in the boat-tail of the diffuser is a wide slot, so I believe these ducts blow the starter motor slot. Until other teams cottoned on to Newey’s exploitation of the outer 5cm of floor, most teams pointed their exhausts towards the Starter Motor Hole (SMH), as a way of using the high velocity exhaust gas, to drive more flow through the diffuser and thus create lower pressure for more downforce. With Newey’s outer blown diffuser he could not exploit the large SMH with his exhausts, so this solution allows him to exhaust-blow the diffuser and passively-blow the SMH. By passive-blowing, I mean the exhaust is not used to blow the SMH, but simply the normal airflow over the car. Of course the effect of this passive blowing is dependant on the airflow approaching the ducts inlets. The RB7 has all enclosing bodywork around the gearbox and floor. So airflow could not directly lead to the SMH. So Newey has had to duct flow to this area. It’s unlikely that the flow arriving at these ducts is that powerful, having had to pass around the sidepods and over the fairings covering the exhausts. This is likely to be a small aero gain, albeit one that other teams with similar gearbox fairings could employ. Should the engine mapping ban make the outer blown diffuser solution too sensitive to throttle position, then this duct could receive the exhaust flow to still provide a degree of blown diffuser.

Other details

The T-Tray is formed with the floor and has an opening normally covering by the plank

Away from the unique Red Bull features, the floor exhibits a lot of standard practice for contemporary F1 floors. In Red Bulls case the floor completely encloses the underneath of the car, only a small open section in the t-tray splitter is open. This opening will be enclosed when the plank is fitted to the car. There’s probably a matching section of ballast attached under the chassis that fits in the hole, allowing the ballast to sit a precious few millimetres closer the ground.

An older Red Bull floor (this floor can be purchased via F1-247.com)

With other teams more sections of the floor above the plank are open, and in some cases the base of the monocoque also forms the floor, so the removable floor section has even larger openings.

Enclosed Lower Leading: note the ECU inside the hollow section

The area forming the front lower leading edge of the floor also has to house the Side Impact Tubes (SITs). Clearly with a one piece floor like this, the floor cannot be removed with the SITs still attached to the monocoque. Many teams have the SITs removed with the floor, by unbolting them at the side of the monocoque. This would appear to be the case the RB7 floor. Although not visible in this photo, presumably the removed SITs remain with the car, so possibly this floor is being changed, rather than stored temporarily for refitting.

Such is the tight packaging of the area within the sidepods; space for electronic boxes is limited. We can see a small black box and loom within the enclosed section of floor. Just to the rear of this there appears to be a blue-grey square set into the floor. This is probably a transparent window for sensors to project through, most likely the ride height sensors. Normally three are fitted, one to the left one the right and another at the front or rear, these three ride heights can be extrapolated to provide the engineer with the cars attitude to the track.

Note the wiring for sensors passing around the floor

There is also a reasonable amount of wiring loomed around different areas of the floor. When wiring was seen dangling from Vettels front wing mounts earlier this year, people were quick to assume, this related to wing flex. But instead a lot of the car is instrumented, both for data acquisition but also troubleshooting during the race. In the case of the floor, two measurements are commonly taken, pressure and temperature. Pressure sensors log the pressure beneath the floor, should a car suffer damage in the race, the team can tell from the telemetry if a change in pressure readings are likely to cause handling problems. Equally teams have been known to fit temperature sensors the titanium fasteners holding the plank to the chassis. If these skid blocks, ground too frequently they will heat up. This delta in temperature will alert the team that the plank might be suffering undue wear and cause legality problems in scrutineering.

More pictures from @Jeanbaptiste76


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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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DRS: Optical Illusion why some wings appear to open wider

Having failed since 2009 to make the driver adjustable front wing a tool for overtaking, the driver adjustable rear wing flap has replaced the adjustable front flap for 2011. Known within the sport as DRS, for Drag Reduction System, this is now a proven way to allow overtaking. Within a set of complex sporting rules, the rear wing flap can be pivoted to reduce its angle of attack (AoA). This reduces downforce and drag, allowing the car to go some +10kph faster. This effect is similar to the F-duct stalling rear wings raced last year. Although the DRS effect on top speed is even greater than the F-duct. In theory the larger the flap the more drag can be shed when its activated, however the rules set out certain geometry the flap needs to operate within. Firstly the flap has to pivot within 20mm of its trailing edge, thus the flap must move upwards, lifting its leading edge clear of the main plane of the rear wing. Secondly the slot created between the two rear wing elements must be between 10 and 50mm.

Currently F1 rear wing flaps are only 10-20 degrees off vertical, to bring the angle of attack down to nearer horizontal will require a large change in AoA. With only a 50mm opening, simple trigonometry will prove that to find the maximum reduction the angle of attack of the flap, will require a shorter flap. Although in its normal position, a smaller flap will not be as heavily loaded with downforce as a larger flap, the reduction in downforcedrag will be greater, due to the change in AoA.

To demonstrate the effect I have drawn two wings, one with a large flap and one with a short flap. With the large flap in its closed position you can see a large area of wing exposed in the left of the illustration (shown yellow). When DRS is activated and the wing opens to the maximum 50mm slot gap, the reduction in exposed wing area is noticeable.

Large flap – Closed

DRS: Large flap- wing closed, large amount of wing exposed (yellow)

Large flap – Open

DRS: Large flap- wing open, less wing exposed (yellow)

Now when we look at the short flap wing, the difference between open and closed is far more noticeable, as pretty much only the thickness of the wing profile is presented to the airflow. The challenge for the teams is produce a short flap wing, which still produces the level of downforce of the large flap wing. Also in creating this downforce, the wing must not stall or separate. As the reason for the slot in wings to reduce the airflow separating off the underside of the wing. Moving this slot rearward, by using a shorter flap, is likely to induce this sort of separation.
Small flap – Closed

DRS: Small flap- wing closed, large amount of wing exposed (yellow)

Small flap – Open

DRS: Small flap- wing open, hardly any wing exposed (yellow)

Optical Illusion.
Looking at DRS rear wing in use between different cars creates an optical illusion. Some wings appear to open far more than others. Red Bull and Mercedes are teams who have raced short flap DRS since the start of the season. When their DRS is activated, the slot gap appears much larger compared to McLaren who continue to race with a larger flap. Their flap appears to be only half as much as the other two teams. Although if we could measure it, all three wings are creating the same 50mm slot gap.