Germany Tech Review now on Automoto365.com

My Technical review from Hockenheim is now on Automoto365.com.  With the update on McLarens Blown diffuser, Mercedes and Williams exciting ‘open-fronted’ exhaust blown diffusers, as well as updates from Virgin and Toro Rosso.

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Aero elasticity – Red Bulls front wing

 

A very public exposure of the front wing flexing on the Red Bull was made during the German GP, the analysis by journalist Stephane Samson and photographer Darren Heath, showed the tips of the Red Bull front wing running far closer to the ground than their rivals. While some of these pictures can be explained partly by different ride heights, roll positions or attitude changes, some pictures show the Red Bull front wing in a drooped (anhedral) attitude. This has been backed up by on board footage, where by the roll hoop camera is fixed rigidly to the car and any movement of other sprung parts of the car should remain immobile in relation to the camera. Yet still the RB6 has routinely exhibited excessive movement through out the car speed range.

Aero Elasticity
Since the nineties F1 teams have been exploiting a phenomenon called “aero elasticity”, this is where the bodywork of the car, mainly the wings, flex to alter their aerodynamic characteristics. At first this was largely created by the entire rear wing assembly bending it backwards, then more specific parts of the rear wing and as exposed this season, the front wing of the Red Bull has been visibly flexing.

This flexibility can be for three different benefits, either reduced drag, improved balance or greater downforce. With a rear wing limiting top speed, most attention has been paid to reducing its drag. As mentioned this was first tackled by the top rear wing and endplates being angled backwards by the beam wing twisting. A few pre-season failures leading to big accidents saw the FIA introduce the first bodywork flexibility rules. In order to enforce the rules, the FIA designed the first deflection test, a rig pulls the wing backwards by the endplates and the deflection was measured. While this test stopped this practice, it also set a standard to which the cars had to meet in order to be deemed legal. Thus if the car passed the scrutineers deflection test, it was approved to race. However if the car could flex its wings and still meet the test, then they had an advantage that couldn’t be immediately penalised.
Soon teams sought to reduce the angle of attack of the rear wing via flexing the flap or main plane. Then as the FIA introduced additional deflection tests to circumvent these workarounds, the teams flexed the wings to reduce the slot gap and stall the rear wing (Much like a passive F-duct), again deflection tests and latterly the slot gap separator effectively stopped this practice.

Front wing flex

 
Exploiting aero-elasticity with the front wing has not been to reduce drag for greater straight-line speed, as the front wing produces very little drag. At the end of the nineties teams were using front wings that drooped into an anhedral shape (i.e the tips drooping downwards creating an inverted “V” shape). This placed the wing and its endplates closer to the ground, both of which gained more downforce. Firstly the wing was closer to the ground which increased the ground effect. Up to a point the lower a wing is to the ground the more downforce it generates. Then the endplates role in sealing the high pressure above the wing from the low pressure below it, is improved if the endplate can run closer to the ground. Effectively make it act like an Eighties wing-cars skirt. To prevent this the FIA produced another deflection test; a 50kg (500n) load is applied to the wings endplate, should not produce more than 10mm of movement. Again this had largely stopped the practice of excessive deflection for front wings.

However there were still benefits to be had from flexing the front wing flap that was not affected by this test. Instead the wing has been flexed to main a stable centre of pressures position, flexing the flap downward at speed to reduce the wings angle of attack reduced downforce and moves the centre of pressure backwards, reducing the cars tendency to be oversteery at high speed. There is now a deflection tests to prevent this practice.

Red Bulls RB6 front wing

At some races last year and evident through out this year is the front wing of the Red Bull RB6 flexing at speed. Visible from the on board camera above the drivers head, the front wing tips can be seen to slowly run closer to the ground as the car accelerates. As this is a low frequency movement, the effect can be seen in reverse as the cars brakes from high speed. The wings endplates springing up as the car rapidly loses speed and the aero load applied to the wing diminishes. This was clearly visible from the early season races and as early as the Chinese GP I emailed the FIA about this practice and whether it was deemed legal. They reiterated the standard 500n – 10mm deflection test and suggested the car was legal, not directly countering the point that the wing is seen flexing. While most teams wings will flex at high speed, whereby some movement is often seen as the car brakes from high speed. The amount of movement and the low speed at which it starts to occur are startling with the Red Bull wing. The point made by the FIA to me back in April and again after the German GP in late July was that the car met the deflection test, thus was legal to race.

This flex was seen back in China 2010, not simply Germany

Front wing Load cases
An F1 car makes its own weight in downforce at just 70mph, that’s ~600kg of load on the car, half of this load is from the wings and half from the diffuser, thus the wings create some 300Kg of load at this speed. With the cars centre of pressure being some where near 45% forward biased, this means the front wing is creating something like 140Kg of load, split between the left and right wing each wing is producing 70Kg of load at just 70Mph. this is the speed of the slowest turn at the Hungaroring this weekend and only slightly faster than the hairpin at Monaco! Thus the FIA limit of 50kg is vastly under specified for the actual load an F1 car sees at even the slowest circuits. Its not surprising a team can created a wing to beat the 50Kg-10mm deflection test and yet achieve far greater deflections, suggested to be as much as 25mm, at much faster corners.

How’s this done – is it legal?
An F1 front wing is a complex moulding of carbon fibre bonded to metal sections. Although the flaps and endplate are detachable, from a structural point of view a front wing is a single piece. Mounted at its centre section by pylons affixed under the nose cone, itself stoutly fastened to the front of the chassis. In the eyes of the rules and with the exception of the driver adjustable front flap, the front wing should meet the regulation 3.16 regarding aerodynamic influence:

-must be rigidly secured to the entirely sprung part of the car (rigidly secured means not having any degree of freedom);

- must remain immobile in relation to the sprung part of the car.

Therefore the entire assembly can not be allowed to move in relation to the rest of the car. However no car can be 100% rigid and F1 cars are subjected to huge aerodynamic loads, hence the reason for the FIA to set the deflection test. If the wing can meet the test and still deflect above the test load, then the FIA deem it legal and the car can race. This could be achieved by accident or by design. Its possible that the carbon fibre lay up creating the wing will continue to deflect in a linear way all the way from zero load to 50kg and then for loads of 50kg upwards. It’s reasonable to assume most teams wing respond this way. However it’s possible to alter the layup of the carbon fibre or add some from of mechanical system (i.e. hinges or springs) to allow a non-linear repsonse to create the 10mm of movement at a 50Kg load, then create greater deflections above 50Kg. Thus the engineers could create wing that meets the deflection test, but would then deflect down to a desired ride height at a specified maximum speed.

While this is against the “spirit of the rules” which prohibit flexible bodywork they meet the test as defined by the FIA for flexible bodywork, thus the Red Bull and the Ferrari front wings are free to race in the eyes of the FIA.

I have again emailed the FIA to ask about additional deflection tests and have yet to receive a response.

Red Bull Map-Q: The secret to the teams Q3 pace

As explained in my post on ‘EBD’s’ – Exhaust blown diffusers (http://scarbsf1.wordpress.com/2010/06/25/exhaust-driven-diffusers/), teams blowing their diffusers rely on the throttle being open to keep airflow passing to the diffuser. Without this airflow, the diffuser loses downforce and the driver suffers a loss of grip or balance just as he enters the corner. 

While careful design and how the exhaust is placed in relation to the diffuser, can alleviate some of the problems, any benefit from blowing the aerodynamics will be reduced when the throttle’s closed and no exhaust gasses are flowing. 

It’s been reported that Red Bull are following a practice that was used on turbo cars (i.e. the old F1 turbos and WRC cars) to keep the turbo spooled up. By means of retarding the ignition when the driver is on the overrun as he slows for a corner. If Red Bull can keep the flow out of the exhaust pipe relatively constant, even when the throttle is closed going into a turn, then the diffuser will see a more consistent air flow and maintain downforce. Relieving it of the onoff throttle sensitivity so often a criticism of EBD systems. In effect an antilag system is trying to do the same as the Red Bull EBD mapping, maintaining a constant exhaust gas pressure, on or off the throttle. 

Ignition normally occurs within the cylinder, driving the engine

 

When an engine is running normally, accelerating with the throttle open, the ignition of the fuel and air takes place inside the cylinder above the piston. The expansion of the gasses drives the piston and turns the engine. 

After ignition, the exhaust valve opens and the cooler gasses rush down the exhaust pipe

 

During this process the gasses then escape into the exhaust pipe as the exhaust valves opens. As the burning has already occurred the gasses are some what cooler, the then temperature of the actual ignition. This means the exhaust gasses flow down the exhaust pipe with some speed and energy. 

On a closed throttle, little air or fuel are burnt reducing the exhaust gas flow

 

When a driver lifts off the throttle, the engine does induct much air, nor burn much fuel, as a result the engine slows and the exhaust flow also slows down. It is this problem that affects the diffuser, as it sees less exhaust flowing through it. 

With retarded ignition, the mixture burns in the exhaust creating a flow of gasses through the exhaust

 

What Red Bull do is retard the ignition and maintain some throttle and fuel to allow combustion to continue to take place. However the ignition of the air and fuel mixture now takes place later in the engines revolution, when the exhaust valve has already opened. Rather than driving the piston down, the explosion of the mixture goes into the exhaust, still expanding as it does so. This creates a rush of gas through the exhaust mimicking the effect of running with the throttle open. Thus the diffuser still sees a flow of gas and maintains downforce despite the engine slowing down. 

Retarding the ignition overheats the exhaust components (red)

 

Of course this gain doesn’t come for free, the heat of combustion now takes place in the exhaust port, so that the exhaust valve, cylinder head and exhaust pipe all suffer excessive heat. This will affect them, as they cannot withstand this sort of thermal load for long periods. Equally the process burns additional fuel, in the race this is a negative thing as fuel is limited and no refuelling is allowed.
This ignition retard mapping would be controlled via the SECU via the driver selecting a steering wheel control, using quite normal tuning parameters and not some clever workaround. Of course this is all quite legal. 

If the overheating issues can be contained, this would be a relatively simple mapping to introduce for another EBD team. As mentioned Renault Sport, Red Bulls engine supplier would have to know about this. Copying the concept, but not the actual SECU code would be quite easy.

Valencia: Technical review now Automoto365.com

 

My Technical review is now online at Automoto365.com.  With the latest updates across the grid.

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Valencia: Technical Review now on Racecar-Engineering.com

My Technical review is now Racecar Engineering Magazines Website. With News on the Ferrari, Renault and Mercedes blown diffusers, Red Bulls and williams Vaned double diffusers, Everyones f-ducts and all the new bits on the cars including Ferrari, McLaren, Renault and Williams.

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Ban on Outboard Mirrors – Red Bulls prototype mirror

Red Bull - Rapid protoyped mirror (Copyright: autosport.com)

With the forthcoming ban on outboard mirrors, teams are using the chance to have the driver and car together to size up their new solution.  Here we can see Red Bull have made up a Stereo Lithographed – Rapid Prototype mirror.  It’s been taped to the cockpit so the drivers can judge its position, ready for the monocoque modification and final production mirror housing to be ready for the Spanish GP.

Red Bull: Exhaust Driven Diffuser

Red Bull surprised everyone with their revised car that appeared on the last day of testing.  As the car sported revised exhaust systems with a low exit that aims the exhausts over the diffuser.  While exhaust driven diffusers were popular in the nineties before periscope exhausts became the norm, to have the exhaust play over the top of the diffuser is a relative novelty.  However the Newey designed solution on the RB6 is a little more complicated than it first appeared.  In one shot we can see the upper deck of the diffuser features a window (Arrowed) to allow the exhaust gas to pass inside the diffuser, rather than solely over it.  With the aim that the high speed exhaust gas will drive more flow through the diffuser to increase downforce.

One criticism aimed at exhaust driven diffuser is their sensitivity to the throttle position and hence the speed of the flow through the exhaust and in turn the amount of downforce it adds to the diffuser.  This issue was mainly related to when the exhausts   were placed right on the kickline between the floor and diffuser, thus their effect on downforce was much more pronounced.  Placing the diffuser further up the diffuser reduced this sensitivity.  Newey knows a thing or two about blown diffusers, the McLarens retained diffuser exhausts exits all the way to the MP4-17, even then the switch to periscope exhausts was largely driven by other  engine packaging factors.  Even the still born MP4-18 aimed to have diffuser exiting exhausts.  The placement of the exhaust some way upstream of the diffuser exit should allow a better compromise between downforce and sensitivity.

Red Bull: Jerez developments

Red Bull: Revised front wing endplates, with a slotted side and new cascades

Following their evolutionary theme for the RB6, last week their car appeared with a logical development to the RB5 front wing.  As with much of the aero on the Newey designed car, the approach is unique.  Red Bull have a wing highly integrated into the endplates, with the flap and two slots hard to distinguish from the endplate and main plane.  

One feature common to many cars is the Brawn style upright-less endplate, Red bull have not followed this path and the endplate still features a large upstand along its upper edge.  The upright-less design directs more flow low around the wheel, to replicate this Newey has followed some other teams and vented the side of the endplate to accelerate the flow inside the endplate, creating the more powerful flow around the front tyre. 

Allied to the vented endplate the new front wing also sports revised cascades, still split into two span-wise sections,.  But the two sections are now more aggressive and flanked by endplates.

RedBull RB6: First impressions

RB6: a more raised V nose

RB6: Pull rod rear suspension has been retained

RB6: tall and narrow diffuser

RedBull surprised us all last year with a car far different to its rivals. Neweys nose up tail down approach was all about working the diffuser and rear wing harder. Even in its early format the RB5 was a match on pace for its double diffuser equipped peers. However the 2009 ar car was ill equipped to accept a doubel diffuser, the low mounted gearbox and crash structure impinged on the space needed for the diffuser. Its clear Newey has kept the basic conept of the car and redesigned the rear end to accomadate the bigger diffuser. While taking what was a unique and now more commonplace “V” nose to a greater extreme.

The whole front of the chassis appears to have been raised, but it is in fact the bulges formed by the tips of the “V” nose that are higher, Newey has done this to create a narrower cross-section down low, for more space between the front tyres to route airflow through the undercut sidepods and over the diffuser and beam wing. These shoulders atop the chassis no longer merge smoothly into the nose cone but are more truncated, the main shape of the removeable nosecone is now near hexagonal, and very shallow, drooping slightly toward the two camera pods mounted hammer head style at its tip. Beneath it is a derivative of the 2009 front wing with its complex curves and three element main plane bridged by the two element cascades.

Moving rearwards the roll structure, raised chassis, splitter and bargeboards all appear to be largely carried over from its predesessor. Although now housing a larger fuel tank.

The pod wings also take cues from the RB5 with the mirrors mounted on slim extensions from the top of the board. From the high and realtively small sidepod inlets the sidepods start off undercut and then turn into a downward flared shape as per the 09 car. diping along with the exhaust outlet under the rear suspension. The rear suspension is still high mounted and retains the pull rod suspension, but is not merged into the tail fin and not exposed atop the gearbox. The tail fin now features a far larger side area, and incorporates the tubular outlet and optional slots for engine cooling. the rear wing is endplate moutned, there appears to be no central support strut. and although the shark fin joins the rear wing this does not take the loads from the wing into the chassis.

At present the diffuser isnt fully evident, nor is the rear crash structure, which are likely to be the areas where the car diverges from its forebear.  What we can see is the launch diffuser (which may well change before Bahrain) is a long, narrow affair.  Merged into the tail of the cokebottle shape and featuring staggered exits to maximise the use of bodywork heights allowed at the rear of the car.