McLaren: European GP wing movement

UPDATE: While I am still awaiting a response from McLaren, I have had a direct reply from Charlie Whiting, FIA Formula One Race Director, to my questions. He responds “The slight anomaly you refer to has been investigated and we have told the team improvements need to be made”. I also asked if this area is subject to any specific deflection tests or construction of the wingpylon interface “there is no stated permissible deflection of the parts you’re referring to, we do of course have a blanket restriction on any bodywork moving but, in some cases, we define limits given that no bodywork can be designed infinitely rigid”. So it seems any movement there should not be evident at the British GP.

McLaren sported a new front wing at the European GP last. Although the endplates, main plane and cascades were all new, it was the way the wing mounted to the nosecones pylons that has caught attention. From the onboard Tv footage the wing can be seen to apparently and progressively separate from its mounting. However this movement is caused, it is likely to spark questions on flexible aerodynamics, although its clear the McLaren was passed as legal by the FIA scrutineers checks.

http://www.twitvid.com/NLDQ1 Video via Ian Doreto

As McLaren place their camera pods on the front wing pylons (the two vertical plates bonded to the nose cone) and also slightly behind them, the onboard footage presents a clear view of the side of the pylon and the wing below it.

Typically the construction of this area is relatively simple. The wings central section has a metal plate bonded to it, through which run threaded studs. These studs pass up inside corresponding holes in the pylons and are then fastened down with nuts. This makes the assembly rigid, with no freedom of movement. Teams fit a spacer shim into the gap, to ensure the wing sits at the correct static ride height when fitted to the car. Almost every team follows this basic design.

However from the onboard footage, it appears that the McLaren wing is hinging on the pylons allowing the wing to rotate backwards slightly. What can be seen is a gap incrementally opening up at speed towards the rear of the interface between wing and pylon (pictured above). Then as the car slows, the gap closes back up to nothing. I have seen two onboard shots of both the cars in the race and both appear to behave in a similar way (pictured below).


This would have the effect of flattening the front wings angle of attack at speed, decreasing downforce. Depending on the way the diffuser sheds downforce at speed, this would have the effect of inducing understeer, probably for the purpose of making the car more balanced and stable for the driver at high speed. The practice of flattening front wings has been seen before, historically it’s not been unusual to see a front wing flap flatten out at speed, as the compliant flap is subject to aero load.
By achieving a better aero balance at speed, this achieves a different effect to the Red Bull, which appears to droop the front wing into an anhedral shape at speed, this creates more downforce rather than shedding it. So Red Bull are seeking more performance, rather than managing the cars balance.

McLarens wing behaving in this way could be explained in several ways, perhaps as the result of a manufacturing fault, I will ask the team if they had any such problems with the new front wing in Valencia.

I have heard previously from several ex-designers and technical directors, that even in recent seasons teams have had springs in designed into this area. Designed in such a way, that a gap opens up by creating some compliance in the wingpylon interface. Normally by having a sprung mount, the spring being preloaded to meet any FIA test, but above the FIA load the spring is able to move the wing in a controlled manner. This is of course a far easier way to control the wing than compliance designed into the carbon fibre lay up. The rules do not specifically state that such compliant mechanisms are banned, although a similar wording has been created for the T-Tray splitter mounting. Following the precedent of the Red Bull front wing, which also appears to move at speed, it seems that any movement of the wing is allowed as long as the wing passes the FIA deflection tests. Which is in turn contradicting the FIA demand for bodywork to be rigid and having no degree of freedom in relation to the body/chassis unit.

3.15 Aerodynamic influence :
With the exception of the driver adjustable bodywork described in Article 3.18 (in addition to minimal parts solely associated with its actuation) and the ducts described in Article 11.4, any specific part of the car influencing its aerodynamic performance :
- must comply with the rules relating to bodywork ;
- 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.

McLaren rear end: Exhaust, cooling and suspension

 

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

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

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

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

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Trends 2011 – Exhausts and Diffusers

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

Double Diffusers

Force India 2010 Double Deck Diffuser (DDD)

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

Single Diffuser

Double Diffuser

 

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

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

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

Outer Blown Diffuser – Solution

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

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

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

Front Exit Exhaust

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

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

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

McLarens Slit Exhaust

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

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

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

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McLaren preseason rear end update

20110318-093655.jpg

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

20110318-093710.jpg

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

20110318-093727.jpg

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

20110318-093737.jpg

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



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McLaren MP4-26 exhaust – is the “U” bend a Front Exit?

 

MP4-26 - the "U" bend is visible between the diffuser and suspension

McLaren lead the way with innovations in 2010 with the F-duct, but they were late to debut their double diffuser and blown diffuser. In 2011 McLaren appear to be right on the tail of this year’s novelty the front exit exhaust.
So far in testing, the MP4-26 has been seen completing a diligent aero programme with the car appearing with two different format exhausts. One conventional set up which blows over the diffuser and another which appears to have a “U” bend in the system. This latter solution is believed to be a front exit exhaust as used by Renault (http://scarbsf1.wordpress.com/2011/02/01/renault-r31-front-exit-exhausts-fee-explained/).

But as yet there is no sighting of the actual exhaust outlet.

Last year teams started to blow the exhaust over or through the diffuser to produce more downforce. With the method of opening the front of the diffuser up and letting the fast moving exhaust blow inside the diffuser, being the most effective route for more aero grip. Rule changes for 2011 prevented teams opening the front of the diffuser up (aside from a 5cm outer section of floor). So teams are faced with either blowing less efficiently over the floor or finding a new way. Renault have exploited another way, by leading the exhaust forward and pointing it under the front of the floor. Blowing the exhaust at the leading edge of the floor effectively creates more flow under the floor, which in turn creates more downforce. This front exit is a good aero solution, but packaging the duct from the main exhaust to the front of the sidepod is difficult due to the space constraints within the sidepod and heat rejected from the exhaust duct itself.

MP4-26 the conventional exhaust exits at the rear and blows over the diffuser

With McLaren’s conventional exhaust the four pipes merge into the collector and the secondary exhaust pipe points backwards to blow flow over the ramped outer section of diffuser. This set up has been used on and off consistently through the test. It also appears to the baseline configuration. As a lot of the aero tests using pressure rakes, flow-viz and long runs, are being completed with the conventional exhaust.

MP4-26 with the conventional exhaust exposed, the "U"bends crease in the floor can be seen

However other tests have been completed where the sidepod is revised. The sidepod features a bulge at the rear of the coke bottle, the bulged section appearing to house a revised exhaust system. Looking from the rear where the normal exhaust outlet can be seen is instead a “U” bend of exhaust tubing. With this set up the exhaust exit cannot be seen. Although several photos of sensors and cabling around the sidepodsplitter have prompted some fans and media to propose they are exhausts. In my opinion no photo as yet exposed the real exhaust outlet. With both systems, the rear of the floor and diffuser are the same.

MP4-26: This is how the "U" bend exhaust might look

Knowing the “U” bend system exists, I’ve tried to find proof for a front exit. One bit of evidence is on the launch car, which was initially unveiled without bodywork. Clearly a lot on the car was missing, but the floor appears definitive enough and just below the normal exhaust collector was a crease in the floor. This niche moulded into the floor is in the same location as the bulge in the sidepod when the “U” bend is run. Looking at its shape, I’d suggest this is where the collector and secondary pipe sit when the “U” bend exhaust is fitted. We can roughly predict that the collector sits further outboard and a little lower. The secondary pipe then curves inboard and then forward under the branch of four primary pipes (see illustration). Of course from here we don’t know where the exhaust routes, so we can’t confirm if it does blow back under the floor.

MP4-26: this is the aero rake used to measure flow accross the floor

Amongst the various aero rake tests McLaren have run, some tests features a huge array of pressure sensors in a rig mounted behind the diffuser. A later test had a simpler rig, which passes the floor ahead of the rear wheels. Initially this system ran with a conventional exhaust, and then later the rake was run with the “U” bend. I believe the rake was used to look at the pressure distribution under the floor. The two runs were used to map the different between the conventional exhaust and the improved flow of the front exit. So this suggests they are running some form of front exit.

MP4-26: the aero rake and "U" bend being run simultaneously

So where is the exit? I’ve looked at every picture I can find of the MP4-26 and I have yet to see any evidence of the front exit. I do believe its there, hidden behind the bargeboards somewhere below the sidepod inlet, or routed inside the splitter and blowing backwards. Other journalists at the Jerez test have confirmed some form of exhaust exit appears to be in there, kept out of sight both by other bodywork and the huddle of mechanics around the front of the car with the portable blowers to keep things cool when it returns to the pits. Also I’ve heard that the switch for one system to another takes 2 hours, which has reduced the McLarens track time.

But until we see a photo of the exit we can only speculate.

Notes:

This is not an exhaust

 

This is not an exhaust

 

This is not an exhaust

McLaren Roll Hoop and Cooling Arrangement

 

McLaren have adopted ideas from other teams with the cooling set up for their MP4-26. With the return of KERS, having to package all the hardware and its cooling requirements is a challenge. McLaren want to reduce the volume within the sidepods for aero benefit, so anything the team can do to resite cooling to other areas of the car will be an advantage. Thus the team have developed a car with three inlets around the roll hoop.

Typically all the cars coolers are fitted within the sidepod and fed by air from the sidepods inlet. An F1 car needs to cool the engines water and oil, as well as the gearbox oil and the hydraulic fluid. KERS places an additional load as the MGU and batteries each need to be cooled (via oil and water). With the 2010 move to no refuelling, the fuel tank had to be increased in size. The bigger fuel tanks robbed the sidepod of space and the recent emphasis on airflow to the diffuserrear wing also creates a demand for smaller sidepods. Over recent years teams have fed the gearbox and hydraulics coolers above the gearbox and fed via different methods from the roll hoop. Typically this is either a dedicated inlet (as per the Williams FW32, Force India VJM03) or by splitting the main inlet snorkel above the drivers head (Ferrari F60-F10).

McLarens 2011 solution is to provide a dedicated feed for each of the different cooling requirements. The engines main coolers reside within the sidepod, fed by the “L” shaped inlets. These vent partly through the rear of the sidepod and partly through the bulge in the tail of the upper engine cover. Equally the engines induction system if fed by the snorkel formed by the roll hoop, which leads into the airbox above the engine.

McLaren MP4-26 airbox inlet flow

Then McLaren feed the gearbox cooler with an inlet moulded behind the roll hoop, this leads down to the cooler behind the airbox and vents via a dedicated tube out the back of the car.

McLaren MP4-26 gearbox cooler flow

Lastly the KERS system is mounted beneath the fuel tank as one component. The entire KERS is cooled by a dedicated cooler mounted behind the roll hoop and under the airbox snorkel. This gets fed from air passing just above the drivers helmet and under the snorkel. From straight ahead the coolers aluminium matrix can be seen through the hole. Heat rejected from the KERS cooler then vents out the back of the engine cover.

McLaren MP4-26 KERS cooling flow

With all of these inlets McLarens reduced sidepod shape, has lead to some compromises. Which is has been to adversely affect the airflow approaching the centre of the top rear wing. Equally inlets create drag and McLaren have two additional inlets to account for. I doubt the cooling set up is a major differentiator between teams. But the different approaches do create some welcome variances in appearance between the cars.

Footnote:

Those little inlets inside the main ones are for cooling the electronics and hydraulics within the sidepods.  Most teams have inlets positioned just inside the main sidepod inlet.

McLaren MP4-26 – “L” shaped sidepods

Airflow passes over the sidepod to the beam wing (yellow), while an undercut still directs flow the sidepod

With a lot of expectation around McLarens new car, the newly unveiled MP4-26 did indeed surprise with its sidepods. Termed “U” shaped by Technical Director Paddy Lowe, as the two “L” shaped individual inlets together form a “U”. As with other design elements on the McLaren these are almost directly opposite to what the rest of the grid is doing.

What the team have done is to shift the inlet for the radiators at the front of the sidepod as far outboard as possible, to allow a freer flow of air to the rear beam wing (the lower element between the tail lamp and the top rear wing). Typically teams place the inlet for the radiators as close inboard a possible, as this airflow is the cleanest and with the most energy. This allows the sidepods to cool efficiently and hence have smaller inlets for less drag. By placing them outboard the vertical inlet catches the turbulent airflow from the front wheel wakes. Its this messy airflow teams try to keep away from the car with the pod fins. While McLaren may have to have a slightly larger inlet to cope with the poorer airflow, the benefit is that the better airflow closer the centre of the car can now be directed at the beam wing. With the double diffuser banned, a larger proportion of rear downforce will have to come the from the rear wing.

Also by creating this shape inlet it means McLaren cannot have the deep undercuts in the sidepods, which other teams use to direct the airflow around the sidepod and over the diffuser. McLaren have still managed to keep an undercut, but this is much smaller and lower, at about the same as the bottom of the raised nose.

Packaging radiators and ducting into this shape is far more complex than a simple inlet. The radiators themselves have a stepped upper edge, the protruding section reaching up inside the higher “L” shape section of sidepod. This makes the duct that directs air from the inlet to the radiator much simpler.

It remains to be seen if this set up works better than conventional undercut sidepods for creating rear downforce. Others team would be able to recreate the McLaren “L” shaped sidepod inlets. Although it would require a significant change the radiators and bodywork, making it a major package upgrade and not a quick test. For those teams that have not already tried this idea in the past, they will certainly being giving it some simulation time over the next few weeks.