Analysis: Raised Rear Wishbones

susp_oversized_RLWB-complete

For many years the shape and position of the cars suspension elements have been an important factor in the cars aerodynamics. For 2013, almost every team have taken the same approach pioneered by Red Bull in 2012, by raising the rear lower wishbone. In doing this the teams have also oversized the wishbone’s cross section to enclose the driveshaft. It transpires that there are two gains from this practice, primarily improving flow over the diffuser and secondarily reducing the aerodynamic effect of the spinning driveshaft.

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Analysis: Red Bull DDRS

It’s rare a technical development passes without anyone noticing and of all teams its surprising Red Bull pulled off that trick in the past few races. As they were seen to have a Mercedes-like Double DRS (DDRS) system in use in Japan. It transpires the system was track tested in practice at Monza and raced in Singapore. Part of the secret of the Red Bull DDRS is that the system is wholly contained within the rear wing. Only the plate over the end of the rear wing flap gave away the systems existence. With this system Red Bull are able to shed even more drag when DRS is open, thus giving them a top speed advantage in qualifying and when DRS can be used in the race.
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Monza: Rear End Analysis

One of the most insightful views of an F1 car is from the rear. From this angle we can easily assess the amount of rear wing, cooling, exhaust position\effect, suspension geometry and important elements of aero\diffuser design. At Monza this weekend XPB images kindly allowed us to show these images, which clearly show different elements of some of the cars running this weekend.

Ferrari


The F2012 has followed its own aero philosophy, so it looks different to many other cars from the rear. For Monza specifically we can see the low drag rear wing, much shallower than the usual rear wing and with the “V” cut outs on the trailing edge. Also for Monza Ferrari cut down the beam wing, the small amount of drag the beam wing creates is reduced by slimming the outer spans of the wing, to reduce the tip vortices.
Ferrari’s sidepods are laid out differently to other cars, most of the cooling outlet area is on the flanks of the sidepods, through the Acer ducts and in the area of the tail of the coke bottle shape. So when we look at the car from the rear, the central tail funnel cooling exit is not present. This design may hinder flow in the coke bottle area, but does leave far more airflow to reach the rear wing. Additionally several cooling vents are made in the narrow bodywork around the gearbox.
Around the diffuser Ferrari have gone further than other teams, with the aero parts around the perimeter. Teams often fit gurney flaps or flaps at the diffusers trailing edge to lower the pressure behind the diffuser and encourage more air to pass through the diffuser for more downforce. In Ferrari’s case the diffuser now sports two flaps above the diffuser, one lower down and the larger one above. This larger one is clearly visible, the lower one is mainly visible through the arched shaping. Having a two element design to this flap means it can be angled more aggressively to have a greater aero effect.


Along with trailing edge the flap the tall flap formed under the crash structure has also gained a two element design. Evident in this picture is the starter motor hole, the end of the shaft that the starter motor engages with is clearly visible through it, but although the starter motor shaft is round the resulting hole is far from circular. Teams exploit the ruling for this opening, by making the hole a blow slot to improve airflow through the middle of the diffuser. Rules dictate only one hole must be used and of a maximum surface area. In Ferrari’s case their two holes are joined by a small slit to make them effectively one hole. Most teams exploit this area in one form or another.

Lotus


In comparison to the Ferrari the Lotus is a more conventional shape with the sidepods, although the exhaust position is evidently different. As Lotus are one of the most successful teams to race this year without a downwashed exhaust solution blowing the diffuser. In the case of Lotus the exhaust blows into the duct formed by the rear wing. Cooling for the E20 is largely exited through the middle tail funnel.
For Monza this wing is very small indeed, the reduced drag helping the Renault powered Lotus reach higher top speeds on the long straights of Monza. Unlike other cars described here, the Lotus beam wing is not waisted away and also retains the taller flap exploiting free bodywork zone the middle 15cm of wing span. Also interesting to note with the tidy rear end of the Lotus is the extreme convergence of the wishbones where they meet the gearbox.


There are two distinct features on the E20 diffuser exit; the side exits and the trailing edge flap. Lotus expands the diffuser not only upwards but also outwards, such that the diffusers exit passes sideways out of the maximum 1000mm width allowed for the diffuser. This increases the diffusers expansion ratio, for more downforce, the trick being keeping the airflow attached to the aggressively shaped diffuser walls. Above the trailing edge Lotus fit a flap in-between the rear wing endplates.

McLaren


McLaren is very similar to Lotus with the conventional sidepod and cooling arrangements, of course McLaren exploit different exhaust positions, with the side exiting exhaust being downwashed to blow the side of the diffuser. The central cooling funnel has been augmented by two small outlets near the cockpit. These sit just inside the free area for sidepod bodywork, any further outboard and they would be subject to the strict rules on openings and curvature in the sidepod bodywork.


McLaren run a low incidence Monza spec wing, but this is not as slim as some other teams. Likewise their beam wing is slightly revised with the outer tips eased off to reduce drag they create. Below this the diffusers trailing edge is treated to a flap around most of its perimeter and inside the diffuser large single opening for the starter motor is apparent.

Red Bull


The unique shape of the RB8 is apparent in this image, the sidepods blend into the gearbox and rear structure freeing up airflow to the diffuser and beam wing. This is possible because so much cooling flow is ducted out of the central tail funnel. Although for the heat of Monza extra openings are created in the lower flanks of the sidepod. Drag reduction is aided by the beam wing being shorn of its central peak. Resulting in a “V” shape dip in the beam wing. Below the tail light a small electronic device with cabling emerging from it is visible. This is the back up timing transponder. The primary transponder to signal to the timing system sits under the nose of the car. Being mounted in the position, the transponder is exposed to potential damage, so teams fit covers over the device to protect it.

Timing transponder position as described in the Appendix to the FIA Technical Regulations

The exhaust position is clear in this image, the exhaust outlets despite pointing upwards, is actually diverted downwards by the downwash over the sidepods and the coanda effect of the sloping tail of the sidepods. These effects deliver the exhaust gas to the edge of the diffuser for a greater sealing effect. This sealing effect is critical as the Red Bull runs the car with a high rake angle, which is a low front ride height compared to the rear ride height. We can see the edge of the diffuser is nearly as high as the rear wheel rim; this rim is about 15cm high, so with the 5cm under floor step the rear ride height must be near 10cm.


Similar to other diffusers, the RB8 also sports an arched diffuser with a trailing edge flap. However, Red Bull curves the flap downwards over the arched sections, this results in a small flat edge on the flap above the arch. Due to the way the carbon fibre is finished around these flats, they appear like openings from some angles and have been mistaken for blown outlets. Lastly Red Bull continues to use extended rear wing end plates that form vanes behind the diffuser. While other teams have used this design, they have raised the bottom of the vanes to only sit in the wake coming over the top of the diffuser, not coming out from under it.

Williams


Aside from their waisted gearbox creating nothing but open space ahead of the beam wing, Williams follow many of the principles seen on the other cars in this article. The rear suspension geometry can be clearly seen with the near horizontal top wishbone and far less convergence in the top\bottom wishbones compared the Lotus. While the steep angle of the driveshaft’s shows just how low the differential is placed. In this picture the lack of cooling outlets on the Williams is apparent and very different to the Red bull & Lotus who run the same Renault engine.


For Monza the beam wing has been dramatically slimed down to reduce drag on the straights. While the diffuser sports a trailing edge flap and tall curved vertical gurney under the rear crash structure. Like many teams William paint the cover of the rear timing transponder in fluorescent paint to make is clear to the rear Jack man to avoid it during hurried race pitstop.

Red Bull: Ducted Sidepod and Blown Starter Hole

Red Bull have raced two major iterations of sidepod and exhaust this season, at Valencia they introduced their third. This iteration brought the re-introduction of the bridgetunnel concept first used with their V2 sidepod. These sidepods not only sport a single tunnel, but the inlet is split to feed two different flows inside the bodywork. Initially mistaken as a double floor or double diffuser, This V3 sidepod sees a return to the duct blown starter motor hole raced in 2011.

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Renault: European GP Alternator Failures

At the European GP in Valencia we saw the unusual circumstance of two ‘leading’ cars both retire within a few laps of each with a related fault. It was confirmed by Renault that there were alternator failures on the Renault Engines of Vettel’s Red Bull and Grosjean’s Lotus. Typically the alternator in a Modern F1 car is unseen and causes almost no issues, so this is an opportunity to look at this component and the failures in Valencia.

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Red Bull: Front Hub Rule Clarification

Coming straight after another Technical Directive from the FIA, Red Bull have again had one of their designs ruled on by Charlie Whiting. It’s now the Front hub design that has stretched the rules to the point where a clarification was required. Uniquely Red Bull duct air through the front hub to vent it out through the wheel for aerodynamic benefit. This appears to contravene the regulations on air ducts forming part of the brake system.

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Red Bull: Bahrain Sidepod Analysis

Having been slightly off the pace in the opening three races, Red Bull clearly do not have the RB8 working as they had expected. Pole position in Bahrain doesn’t prove their issues are over, but the car sports a revised sidepod set up this weekend and this has perhaps has unlocked the potential in the car. The new sidepods are a revision of the Version2 spec sidepod/exhaust set up. The Bahrain spec simplifies the sidepod, removing the complex crossover tunnel under the exhaust ramp.

Exhaust Versions

Sidepod Version1

At the cars launch the RB8 features a simple Version1 exhaust set up, aimed at being a benign solution to get the bulk of testing out of the way, without interference from complex exhaust issues. Then later in testing the focus could switch to the greater potential performance offered by the V2 set up. The V1 set up placed the exhaust in board and rearward, blowing under the top rear wishbone. The exhaust flux blew along the tail of the bodywork and under the beam wing. Despite suggestions at the time that this set up was a novel exhaust blown suspension set up; the solution was never intended for race use.

Sidepod Version2


Then on Day11 of the 12 day preseason testing schedule, the V2 sidepodexhaust appeared. A more complex solution than either the McLaren or Sauber set up, the sidepod aimed to both direct exhaust flow at the diffuser and route the sidepods undercut flow to the centre of the diffuser. To do this the sidepod had a more outboard and rearward exhaust position.

The exhaust blows down the tail of the sidepod, over a ramp made to try to attach the exhaust flow to the bodywork via a coanda effect to direct it in the correct gap between the rear tyre and diffuser. This is the same area the teams aimed their exhausts directly at last year. This area helps both seal the diffuser from flow blown laterally from the rear tyres and also the greater mass flow of the exhaust plume creates more flow through the diffuser, with both effects adding downforce. This solution follows the same path as the much applauded Sauber solution. Although the two systems were developed in parallel and RBR did not copy the Sauber after seeing it launch. The RB8 always was planned to run the V2 set up.

V2: a tunnel is created under the Exhaust ramp bodywork (yellow)

V2: Flow from the sidepod undercut passes through the tunnel (yellow)

To keep the airflow passing over the top and centre of the diffuser, teams direct the fast moving flow from the sidepods undercut to this area. In Red Bulls case, the path of this flow is obstructed by the exhaust ramp and plume. To overcome this Red Bull have simply created a tunnel for the air to pass under the exhaust ramp and remerge towards the centre of the diffuser. This solution looks like is major aim was to direct flow to the start motor hole, an area exploited by ductwork on the 2011 RB7. Having more airflow passing into the starter motor hole, makes the hole act like a blown slot, making the airflow better up and under the middle section of diffuser for more downforce. Creating a crossover effect is somewhat like McLarens bulged exhaust fairing, that allow both the exhaust to be directed down to the diffuser edge by the downwash flow over the sidepod, but also creates a channel beneath the exhaust bulge to allow the undercut flow to reach the centre of the diffuser.
So it seems Red Bulls V2 floor make the best of the Sauber Coanda solution and the McLaren undercut solution.

What are the issues?
However this tunnel is compromised by the post-2009 area rules. Sidepod bodywork 50mm above the floor (actually 100mm above the reference plane) must meet tangential and minimum radius regulations. This means Red Bulls tunnel is limited to slightly less than 50mm in height, with a sharp top edge.


It seems it’s this crossover tunnel on the V2 sidepod that is an issue with the car. Recent flowviz tests in free practice were focussed specifically on the tunnel, as well as tests with an array of aero sensors trailing the diffuser in Bahrain. Also an insider tells me that the Red Bulls starter motor might not be creating the accelerating airflow into the steep middle section of diffuser that was envisaged. Instead the starter hole works better when blocked off. Perhaps this crossover tunnel is not flowing correctly to the centre of the diffuser and altering the accuracy of the exhaust flow towards the tyrediffuser intersection.
If the exhaust flow cannot reach the tyrediffuser gap accurately or perhaps more importantly consistently, then the driver will have a car that sensitive to throttle position.
Red Bull have been alleged to have clever engine mappings, cutting down to four cylinders at larger throttle openings at lower revs. This could either have the effect of a softer power delivery for better traction, of greater exhaust flow for more downforce at lower revs. Red Bull and Renault may still be finding ways to gain performance from exhaust mappings and these mapping have been investigated the FIA and shown to be within the regulations.
With several issues around the way the exhaust affects the cars handling, Red Bull said in China that the V2 sidepod was the potentially better solution, but the V1 set up gave Vettel more confidence. Horner admitted that it was possible to get the performance of the V2 with the feel of the V1. At Bahrain it appears that this is what RBR have done.

Sidepod Version 2.1

V2.1: With no tunnel the exhaust flow can pass without interference to the diffuser

These issues may explain the Bahrain sidepod upgrade. This new sidepod set up appears to be a rework of the V2 sidepod, most of the shape remains the same and the exhaust appears to be in the same position. So it looks like the moulds were altered to close off the cross over tunnel create a V2.1 sidepod.
With the tunnel closed off the issues complicating the exhaust and starter motor hole flow have been cleared up. But there still remains an issue with how the sidepod undercut flow reaches the rest of the diffuser. Sauber appear to manage this, but there still may be some potential airflow performance that is lost with this set up. Although the overall effect of an exhaust aimed accurately at the tyrediffuser gap may be a greater gain that that loss.
However with the tunnel gone there is a less complex route for the exhaust to reach the diffuser. With the exhaust flow better managed the intended exhaust effect will more consistent resulting in a better feel for the driver at different throttle positions and car attitudes.

V2.1: Slots in the floor aid the effect in sealing the diffuser

It’s notable that Red Bull have also reintroduced the slots in the floor ahead of the rear tyres, these haven’t been seen for a couple of years, their function is to inject some higher energy airflow into the gap between the tyre and diffuse. This, like the exhaust blown diffuser, offsets the sidewash (known as ‘Squirt’) created by the rear tyres impinging into the diffuser. Again this will all result in greater rear downforce.

If this is the first solution for Red Bulls woes, then it will be interesting how the team develop from the V2.1 sidepod. Perhaps the tunnel will reappear in revised form or a McLaren style solution will be tried.

Launch Analysis: Red Bull RB8

Car: Red Bull Racing – Renault RB8
Concept
There’s not a lot left to be said about Red Bulls incredible run of pace since 2009. Despite not winning the 2009 championship, the RB5 rewrote the text book on F1 design. Since then, the two subsequent cars have both pioneered new ideas and followed a few others. Each time the car has been ever more dominant. If the team have an achilles heel, then its reliability, split between the; chassis, the engine and KERS. With pace in hand, the team do not need to make bold steps with the cars design, as they need to maintain reliability. With the RB8 taking risks was not on the agenda, the evolutionary car uses detail design and a small few unique features to keep a step ahead on pace.

Layout
With the evolutionary concept, no obvious changes have been made with the cars layout.  The retains a steeply raked attitude, Newey mentioned at the launch that the loss of EBDs will affect their ability to angle the car into the nose down attitude.  But the evidence of the car on-track suggests that obtaining laptime with a lot of rake is not an issue.

Nose

As with many teams, the nose grabbed most attention when the car was launched. But rather than the shock from the awkward looking 2012 noses, there was curiosity over the letter box slots in the nose. There was one more visible slot on the upper section of nose and one less visible one below it.
Rumours circulate that the upper slot is used for some form of F-duct or (non driver) cooling. In my opinion, it is a simple solution to keep the airflow attached over the step in the nose.
Faced with the 2012 rules, Red Bull took the obvious route of a raised chassis and nose. The car now eschews the “V” shape nose and chassis, so the top of the chassis and nose are flat. With the rules forcing a 75mm step between these two surfaces, the airflow doesn’t want to run along the nose and then step up without separating from the chassis top.


So the team has sought to offset some of problems with this design. Red Bulls solution is to create an aero effect to aid the transition between nose and chassis. This starts with the letterbox inlet, which as Newey explained at the launch is ‘primarily’ for driver cooling. The rules permit one opening to the nosecone for the purposes of driver cooling. Normally this is an oval hole in the tip of the nose. But on the RB8 this is a 25cm wide narrow slot and probably only 5mm or so high. As Newey admits, some of this airflow does pass into the cockpit to cool the driver. But what Newey would probably describe as the secondary effect of the slot, is to allow for the rounded leading edge above the inlet. When airflows runs up the nose it hits this leading edge and curls under it, forming a bubble of recirculating flow. This rotating cylinder of airflow helps to keep the upper airflow aligned and attached to the flat top of the chassis. This is a simple and copyable solution. I believe this would work with or without the slot. As the upper section of nose cone bodywork is largely a cosmetic panel and not part of the crash structure. It could be changed without re-crash testing. Sauber have found a similar solution on their nose.
Below the nose there is yet another slot. This in line with the bottom of the chassis and runs the full width of the nose. While I can offer some explanation for the upper slot, this lower one is more of a mystery. Again its use has been rumoured as KERS cooling or blowing the floor, whatever its function I believe it may have been on the car last year. Although the slot was not externally visible on the 2011 car, when the nose is removed the slot was evident below the front bulkhead (pictured below). Presumably this was fed from the driver cooling inlet, which was placed on the nose tip on the RB7.

Clearly the duct formed is very small, which limits it use. I doubt it’s to cool KERS, as the KERS is mounted towards the rear of the car and the small duct would not adequately cool batteries or the like. Its position does suggest the flow could pass down to the splitter, so some clever use for blowing or loading the splitter could be within the realms of possibility. More likely is the use to cool the electronics or power steering rack, which are sited much closer to the duct and would require a smaller amount of cooling air.


One detail of the RB8 and to an extent with the RB7 was the advantage it takes of the radius that is allowed to be applied to the edges of the chassis. This 25mm radius is rounded over to keep the cross section of the nose as small as possible. Within the minimum 300mm x 275mm rectangle the nose must fit into. The top corners of the chassis are clearly a near 3/4 cylindrical section.

Front wing

In common with their rivals the front wing is a derivative of the 2011 wing. Albeit restructured to meet the newly doubled deflection test. Red Bull were late to the endplate-less wing design. Although they created slot in the endplate over the past few years, it’s relatively recently they upper section of endplate has been added on to the tips of the wings, rather than use a conventional separate endplate.

Behind the wing the turning vanes continue the mid 2011 ‘curled’ design.  The vanes hang from below the chassis and are larger this year and sport a split in the middle.

One odd feature visible on the front wing is a small section of removable bodywork in the neutral centre section of wing.  I’ve idea of the purpose of the purpose of this panel, perhaps its to access a sensor or allow ballast to be fitted?

Roll hoop

While retaining the same engine and with the general evolutionary theme of the car, the roll hoop area is indistinguishable from the 2011 car. No doubt there are structural changes under the skin, but these aren’t visually apparent or announced by the team.

SidepodsCooling

Moving onto the sidepods, the general concept of the sidepod shape is also similar to 2011. Slightly triangular inlets feed the radiators, which are mounted horizontal across the car and tilted upwards towards the front. Their flow passes up and around the heat shielding on the engineairbox and most of it exits through the tail funnel. In cross section the sidepods retain the outwardly-tapered ‘jelly mould’ appearance, with only the area under the inlet being undercut. Again as with the RB7 the sidepods merge seamlessly into the gearbox fairing.

Exhaust

Traditionally Red Bull have switched their launch exhausts to their Melbourne spec in the last days of testing. It’s been mentioned by the team that there is a new exhaust system coming. This is no doubt partly the reason for the team delaying the last test and having a near private test (shared with Ferrari) on the last day.
The launch spec exhaust places the outlet pipe inboard and relatively low. This bows in line with the plane of the rear upper wishbone. The bodywork over the gearbox and rear crash structure is curved and creates a neat channel for the flow to pass through. This then sees the exhaust plume pass under the beam wing. In this position the heat is affecting the upper wishbone, even at its launch, the car sported heat shielding over the wishbones. During testing this protection has grown, albeit with temporary looking solutions, suggesting the new exhaust system will not blow in this area.

Rear suspension

The RB8 has a high mounted upper rear wishbone, which places its rear leg in line with the beam wing. In keeping with the recent RBx cars, the gearbox sports a tall spine that functions as the wishbone and beam wing mounting. Although this shaping is partly hidden by the way it merges into the tail funnel.


With such a high top wishbone the lower rear wishbone is able to mount higher too. This wishbone is now effectively at the same height as the driveshaft. Not only is it inline, but the wishbone forms an shroud ahead of the driveshaft to offset the negative aerodynamic effect of the rotating shaft, in the critical area above the diffuser (Note: Fully shrouded driveshafts are banned). While this all appears to be logical, the lower wishbone is not a splayed as the upper wishbone. Having the inboard mountings very close to each other is not so good from a loading perspective, so there must be a reason to make the wishbone in such a compromised shape. Again this might suggest the new exhaust needs the wishbone in a certain position to work effectively.
Diffuserrear impact structure
With the tapered sidepod, the Red Bull encloses the centre of the diffuser inside the gearbox fairing. Other teams leave this exposed beneath the crash structure, to allow flow to pass through and out of the starter motor hole. Last year Red Bull introduced a duct in the floor to send flow directly to the starter motor hole. This year the duct appears to have gone and doesn’t look like it’s been replaced with something. In line with the gearbox and the current exhaust set up, the impact structures forms a spine along part of its length. Once the beam wing is mounted to the spine, the crash structures returns to a normal rectangular cross section and sweeps upwards towards the tail light. This spine format keeps the gearbox and suspension mountings nice and stiff, plus it mounts the beam wing with very little obstruction to it slower surface.

Gearbox
Red bull have used pull rod suspension since 2009 and introduced their carbon fibre gear case in the middle of that year. Keeping the construction and general shape, the gearbox set up appears only have detail revisions over this period.

Aerodynamic features

Every team has exploited the 12cm of space inboard of the rear wheel for aerodynamic bodywork. Red Bull have added particularly large upper vane to the brake ducts this year. Above the top wishbone mounting two large flap can be seen.

The rear wing also exploits a small window that allows bodywork, this makes it possible for Red Bull to fit vanes placed behind the diffuser, to aid the expansion of the flow out of the diffuser.

KERS
It was a bold decision in 2011 for Red Bull to develop their own Battery system for the Renault Marelli KERS. Not wanting to sacrifice wheelbase and fuel tank volume with under-tank mounted batteries, instead Newey mounted the batteries near the gearbox. In fact three batteries packs were fitted, one larger pack either side of the gearbox and a small array inside the top of the gearbox case. Exposed to more heat and vibration the KERS caused problems throughout 2011 and led to the driver having it unavailable at critical points in qualifying and races. I understand the battery positions remain for this year. It was never clear if Red Bull actually had a full power KERS in 2011. The rumours persisted of a Mini-KERS, suggesting the system discharged nearer 40Kw, rather than the maximum allowable 60Kw.

Engine
Announced in mid 2011, Red Bull are now the official ‘factory’ team for Renault. With the success of the team and the Renault F1 team being rebadged to Lotus, This allows Red bull to take a more direct involvement in developing the RS27 engine and the exhaust mappings to maximise what is allowable in the rules.