Racecar Engineering - Formula 1 2019

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CONTENTS 5 7 8 14 18 26 32

Reverse thinking Ricardo Divila asks why racecars still have mirrored glass?

Complicated matter Pirelli’s tyre structure under Mike Blanchet’s microscope Aero gain in Spain One quarter of the way through 2019 F1 has upgrades aplenty S-Duct We uncover the real reasoning behind this clever aerodynamic trick Skirting the issue Simon McBeath applies CFD to skirts in Formula 1 to see what happens Pirelli We look at the challenges faced by Pirelli for 2020, and for 2021 The India formula The CFD model that shows future thinking for F1 2021

Produced by Racecar Engineering team

Danger zone

A

s we near ever closer to the ‘revolutionary’ 2021 season, details are emerging of the proposed regulations which are steering F1 into uncharted waters. In addition to the controversial budget caps, tenders are now out for single supply transmissions, wheel rims and brake systems too. In the battle between controlling the cost and using the sport to develop technology, it seems that the former is favoured.

Having previously worked at Manor Racing, I fully appreciate the efforts to try and reduce costs to make the F1 championship more sustainable for the smaller teams. With the collapse of Manor at the beginning of the 2017 season and the likes of Sauber, Racing Point (previously Force India) and Williams either saved by title sponsors, buy outs, or clinging on to a sponsorship deal, the era of the small F1 team is on life support. This is sub-optimal.

Without such teams, there is nowhere for young engineers, mechanics or drivers to develop their Formula 1 experience. Formula 2 teams are having to expand and become small F1 teams themselves in an attempt to soak up young engineers who want to make that jump into the top tier, a jump which is getting ever bigger. Of course, companies such as Williams Advanced Engineering, McLaren Applied Technologies and Red Bull Advanced Technologies are an excellent development area for engineers, but with the upcoming resource restriction in F1, we will undoubtedly see these companies increase in number. However, these offer little trackside experience.

In an attempt to encourage more teams to remain sustainable in Formula 1, and equalise the performance and therefore competition between the teams, the FIA are aiming to slash costs through limiting access to the sport via a tender process to supply all teams. However, these cost cutting measures are going to significantly affect innovation and opportunity; you don’t need to look far to find just that in Le Mans Prototypes with the LMP2 chassis

constructors limited to just four in number. Your average F1 fan may not get excited about today’s intricate wheel rims which utilise the hot air coming from the brakes to heat the tyres to go a tenth of a lap quicker, but the DNA of F1 is the ‘pinnacle of technology’ and the move towards single suppliers is threatening this philosophy, and taking the concept of innovation with it.

Currently, there are four manufacturers of brake caliper in F1, each pushing the limits of their capability and driving innovation to develop a better product than their competition in a battle to supply more teams. If you cut that down to one manufacturer, not only do you adversely affect the other three in terms of their business, but that drive for pushing the boundaries evaporates. Look at the result of the decision to select a single tyre supplier for Formula 1. I agree, a tyre war is an expensive initiative, but the Japanese cope in GT500, and what motivation do Pirelli have to keep developing their F1 products when their business is secured for the next three years?

Also, how much of a performance differentiator are brake calipers? Andrew Green, Technical Director at Racing Point says that on the list of performance differentiators, calipers are pretty low down. Furthermore, he reckons that the tender will struggle to produce calipers cheaper than Racing Point already does. So, if the tender for brake calipers won’t significantly affect on-track action or reduce costs then the only thing it is achieving is putting engineering companies out of business and sacrificing innovation. The FIA and FOM have a difficult task ahead of them, and their decisions will please only some. But this relentless drive towards standardisation could put the top tier of motorsport in jeopardy, along with many companies within its supply chain.

GEMMA HATTON Deputy Editor

RACECAR ENGINEERING FORMULA 1 SUPPLEMENT www.racecar-engineering.com 3

STRAIGHT TALK – RICARDO DIVILA

Don’t look back in anger Why do racecars still use such old fashioned technology to provide a rear view?

R

ay Harroun, an engineer born in 1879 who was nicknamed the ‘Little Professor’, maintained he only really raced so as to observe his designs being tested in the field.

In 1911, for the inaugural Indianapolis 500-mile race, of the entire 40-car field his yellow Marmon – AKA the Wasp – was the only car to have just one person on board. All the others had a riding mechanic, a bit of a tradition from the previous years of racing on open roads where the early racing machinery, pretty much all prototypes, were prone to mechanical failure or punctures a long way from any assistance. Incidentally, in 1912 the riding mechanics were required by the rules and were then mandatory until 1922, and then returned again in 1930 until 1937.

The knee-jerk reaction from the organisers was to specify that the LMP2s had to have moveable mirrors to shift the focus from the overtaking and blinding LMP1s, but it only made things worse; the vibration moved on to new heights of blur. Okay, part of it was inadequate mountings to damp or restrain the housings, plus they were mandated to be bigger; so more aero turbulence and drag.

Despite changing the mounts, shapes and actuating mechanisms after the test day they still vibrated, so they eventually solved the problem laterally by presenting the cars at scrutineering,

Time to reflect

It proved so useful and practical that it turned into a no-brainer for all racecars built by Nismo since then. The added bonus was the auto-dim feature for the Suzuka 1000km race, which ended in darkness. Audi brought its version out to much fanfare in 2012, much to my amusement, as we had used that solution for 14 years by then.

It was also a primary item on the Deltawing for Le Mans in 2012, a clean, mirror-less design with a camera mounted high on the rear fin relaying an unobstructed rear view to the cockpit screens. We were definitely annoyed when not only did the ACO insist on having the old style mirrors but, adding insult to injury, demanded that the car run LMP2 size mirrors even when running in the Garage 56, with supposedly unlimited rules. This added eight per cent more drag, considerably slowing the car in a straight line.

For that first Indy 500 the Wasp also featured a rear-view mirror, one of the first times such a device had There is now software that has been used – this was inspired by motion sensors that can put a a solution to traffic management coloured arrow pointing to the side Harroun had seen on a horse-drawn of the car an opponent is coming taxi some years earlier when he had up to pass. It flashes faster if the worked as a chauffeur in Chicago. overtaker is closing up fast and In winning that first Indianapolis changes colour from green to red. It 500, Harroun actually had a secret, The trick mirrors on the 2018 Ferrari were as hi-tech as these parts can be, wouldn’t pick up vampires, for as we which he related over 50 years later, but should reflective glass really have a place on a modern Formula 1 car? all know, they cast no reflection, even in 1967. His innovative mirror had electronic, but all else is signalled. reassured his rivals that the racing So, when these days we can have cameras would still be safe, despite him being alone in then siliconing the mirrors in for practice and the guiding us into our parking slot, why not have the car. But the race track at the speedway was race. No more adjustable mirrors but no more the same sensing and warning about traffic and a jarring, bumpy ride; it was, after all, made of vibration either, or at least back to the usual. dispense entirely with 1911 technology; those bricks. ‘To tell you the truth, on the brick surface, I Now, over a century after Harroun’s innovation, draggy, vibrating, limited mirrors? couldn’t see a damn thing in it,’ Harroun said of the we still use mirrors to see behind racing cars. Why? Or why not go the whole hog and throw away mirror. ‘And no one knew it but me.’ the dodgy mirrors and affix a full width OLED This is actually similar to what we still have In 1998 I was involved in running a Nissan GT500 screen to the Halo, electronically enhanced to today. Some rear view mirrors vibrate so much car in Japan, and one of the corollaries of having a highlight approaching racecars. It can even solve that the driver can only see something moving firewall blocking off the 100 litre fuel tanks behind arguments when cars clash, just by recording all behind him, but not very clearly. And then there the driver was having a small Perspex aperture that is seen on the screens. is night racing and the problems that that can for the central mirror that didn’t give us a wide If you don’t like the Halos there’s another present. The ultimate was Audi’s new laser lights enough field of view out the back of the car. alternative, go further and have the view projected with an estimated zillion candlepower fitted to the The solution was to fit a rear view camera directly on the driver’s retina from a projector R18. It was so bright that drivers being overtaken to replace the mirror, and a screen on the dash, on the helmet. Or what about having enough were complaining about being blinded. They lost easily done as one of the team sponsors, which cheap smartphone derived cameras and having a perception of the depth of field, their cockpits was a Nissan subsidiary, was a pioneer in the 360-degree view around the racecar? filled with such light from the frantically flashing manufacture of rear cameras for parking, now a We have the technology, software and following Audis. Even the trackside marshals were standard fixture on medium range cars. hardware. But maybe not the will. getting suntanned in the night stints!

XPB

Looking ahead

Mirror finish

When these days we can have cameras guiding us into parking slots, why not have the same sort of thing instead of mirrors on racecars?

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AZ_FormulaE_102017_190x135mm_03ap.indd 1

18.10.17 08:33

SIDETRACK – MIKE BLANCHET

KISS it better Why the FIA’s list of requirements for F1 tyres is a masterpiece of over-complication

K

ISS – Keep It Simple, Stupid – is a useful still permitted to do). The heaviness of the hybrid2018 US GP, given the effect this has on today’s acronym. It is seldom applied, however, engined cars and the torque being produced, ultra-sensitive F1 cars, is really unacceptable. in F1. The FIA’s 2020 through 2023 F1 plus the increasing downforce also added to their Coming back to the geek in the darkened tyre supply tender document is as far away from problems. However, similar issues confront other room, the FIA’s tender document was littered that desire for simplicity as one could imagine. tyre manufacturers in IndyCar and especially LMP1 with extraordinarily precise requirements such It comprises 19 pages, of which only six and and such problems have not been evident. as peak cornering force per degrees of slip angle a bit cover contractual matters. The new tyre for different types of corner; tyre stiffness versus requirements that comprise the remainder appear temperature working range; deviation of grip Being the one-make supplier, one would think that as if some analytical geek in a darkened room, under a particular condition of surface macro and Pirelli’s job should be a little easier, but its approach hunched over an array of books and downloads micro roughness; glass transition temperature; – not always with a free hand, it has to be said – has on every aspect of tyre design, materials, chemical degradation to 10ths/sec at 10, 18 and 22 per cent varied dramatically. Ranging from tyres that ‘fell properties and molecular structures, drew these up, of race distance; cross linking of the compound off the cliff’ partway through the race (early days) and they have no relevance to real-world racing. polymers, and much more. Pity there wasn’t one Of course, this is surely not true. I that decreed attainment of much greater have no doubt that the FIA has gone to slip angles without losing forward speed. great pains to ensure that input from And then what amounts to a twitch of race tyre manufacturers and teams steering correction in qualifying would combined with loads of its own data not always be irritatingly described by has played a large part in drawing commentators as a mistake, and a quality up the specifications mandated. It is driver’s lurid opposite-lock corner exits certainly long overdue that F1 has could be a delight to us all. the tyres it deserves, to do justice to the qualities of the chassis, PUs, drivers Realistically, I don’t see how all these and engineers now involved. Running characteristics can be reliably and regularly at six seconds/lap below qualifying met, let alone how this can be accurately pace in the early stages of a race to measured. Which are to be the benchmark protect the rubber, even allowing for cars and drivers, for example? The fastest, fuel load, is hardly proper racing. or the slowest? Maybe this could be one of Pirelli, of course, has again won the Pirelli has retained its Formula 1 tyre contract but its race rubber will the reasons, apart from money and politics, supply contract. This is a near 150-year- have to meet a long list of performance criteria to keep the FIA happy why Michelin and Bridgestone apparently old company with an illustrious tyre or barely managed one flat-out lap in qualifying, didn’t bid for the contract? Even in the 2018 manufacturing and competition record, supporting to over-hard compounds described by drivers as season, with all the experience and knowledge of many different forms of contemporary racing. In giving ‘no grip’. Perhaps being Chinese part-owned, the previous seven years, Pirelli frequently failed the early 1950s it was dominant in grands prix, managed by Italians, with race tyres made in Turkey to deliver tyres that provided the key elements in and has been sporadically successful since. It could be something to do with this? race strategy and tactics that were wanted. It’s very currently produces superb high-performance road But I mentioned lack of a free hand above. difficult therefore to see how it will meet these products and is among the top five in the industry Certainly Pirelli’s task has been complicated stringent new demands. Most likely, it will result in worldwide – which makes it a global giant. by confusing calls first from Bernie Ecclestone, a fudge. Should the tyres not be delivering during subsequently the FIA, concerning what was needed 2020, whichever way this is judged, it won’t be At face value then, it’s surprising that Pirelli has to enhance the show. Pretty unfair pressure, really, possible to change supplier quickly anyway. struggled so much since its re-entry to F1 in 2011. from people who don’t fully understand what is Being bolt-on items, tyres are the quickest and Early issues with chunking, overheating and involved in meeting these demands. But it does easiest go-faster solutions, thus their importance. delamination, fragility over kerbs and wheel-toappear to me that the Italian supplier hasn’t (a) They are also capable of contributing hugely to wheel contact etc caused much controversy and resisted such knee-jerk actions more strongly and an exciting race, or to a boring one. Therefore, led to the introduction of regulations concerning (b) is lacking in its simulation tools and skills. it is correct to make stipulations as to their minimum tyre pressures. Pirelli had a fair argument The latter shortcomings, combined with the performance. The question is whether these are for some of this when pointing out that teams were near-disasters at Silverstone and Spa in 2013, practicable and measurable and also if Pirelli can acting recklessly in applying low pressures to gain have doubtless spooked the company and it has deliver. It is to be hoped so, because as already a performance advantage and drivers were overbeen over-conservative since. To insist that teams mentioned it is a great company and should be abusing the track limits (as they are, unfathomably, increase tyre pressures, virtually on the grid of the doing better. F1 needs Pirelli to up its game.

Slick and tyred

XPB

Tread carefully

Under pressure

I don’t see how all these characteristics can be reliably and regularly met, let alone how this can be accurately measured RACECAR ENGINEERING FORMULA 1 SUPPLEMENT www.racecar-engineering.com 7

FORMULA 1 – BARCELONA AERO UPGRADES

Quarter Masters F1 teams have been updating their cars since the start of the season, but the fifth round in Spain saw the biggest aero changes of the year

By GEMMA HATTON

The Spanish Grand Prix is easily accessible for both team members and parts suppliers, which makes step changes in packages a little easier than at the fly-away races

8 www.racecar-engineering.com RACECAR ENGINEERING FORMULA 1 SUPPLEMENT

T

he Spanish Grand Prix marks an important stage in the technical development of a Formula 1 car. After teams have punched out the first race version in time for Australia, teams transition their efforts to developing the first major upgrade package which is usually scheduled for Barcelona. Falling roughly a quarter of the way through the season, by early May teams have had four races to understand the behaviour of their car and establish areas of improvement.

This usually leads to teams arriving in Spain with a significant aero upgrade package which they can test during the practice sessions and decide on Friday night if they should run with them for the race. If not, they have time to revert the changes before Saturday. Furthermore, it is also cheaper to send additional aero and vehicle dynamicists to Spain, who can help monitor the performance of these additional upgrades, and in the worst case scenario, spares can be sent out overnight, in time for qualifying.

Traditionally, teams would bring major upgrades to Barcelona, Canada, Silverstone and Monza, so a quarter, halfway and then three quarters of the way through the season. But as teams continue their rapid development processes, technical upgrades are becoming an increasing occurrence with most teams

incorporating at least something new onto the car each race weekend. Take the example of this year’s pre-season testing where Mercedes popped out a new car for the second test alone!

Apart from Mercedes, these race upgrades are usually one or two parts, such as a new front wing, whereas in Spain, teams can arrive with upgrade packages which can consist of new front and rear wings, bargeboards, radiators, floors, suspension and engine upgrades.

Second wind

The latter was a key talking point at the Spanish Grand Prix, with Ferrari and all four Hondapowered cars running their second specification of power unit. Ferrari has been pushing hard to close the gap to Mercedes by bringing updates to the car earlier than scheduled. In Baku, they introduced significant aerodynamic upgrades one race early and arrived in Barcelona with a new power unit, two races ahead of schedule, as this upgrade was originally planned for Canada.

‘Having started the season in Melbourne we recognised that somehow we may have been late on our performance compared to our competitors and we tried simply to push on all the main items where we were already planning developments,’ highlights Mattia Binotto, Team Principal at Ferrari. ‘When you are planning such

a change to your schedule you need to do it a few weeks in advance and we’ve only achieved this because we have intensified our activities.

It’s only down to a big team effort with everyone pushing hard to make up ground that we have been able to bring these developments forward.’

The power unit upgrade was accompanied by a new formulation of race lubricant from team technical partner Shell to further the PU gains.

Haas on the other hand, will likely introduce their Ferrari PU upgrade at either the Monaco or Canada races. ‘I think doing it at the same time [introducing PU upgrades] is logistically very difficult for Ferrari,’ highlights Guenther Steiner, Team Principal at Haas. ‘Ferrari asked us if we are ok with introducing it [the upgrade] one race or the other and as they need to manage the engine mileage and all that stuff. There is no point in us interfering and we are happy with what they have suggested.’

Tunnel vision

Teams are also targeting their resources at making performance gains through vehicle dynamic and aerodynamic upgrades. ‘We’re constantly developing the current car and we’re aiming to produce upgrades as soon as we’ve found gains in the wind tunnel,’ says Pete Machin, Head of Aerodynamics at Renault F1.

Teams still arrive with significant upgrade packages which can consist of new front and rear wings, bargeboards, radiators, floors, suspension and engine upgrades

RACECAR ENGINEERING FORMULA 1 SUPPLEMENT www.racecar-engineering.com 9

FORMULA 1 – BARCELONA AERO UPGRADES

The Mercedes W10 had modified bargeboards, consisting of three turning vanes instead of two as well as changes to the elements attached to the chassis, ahead of the sidepod

The car at the end of the year will be a couple of seconds quicker than the one that started the season ‘We issue parts to the drawing office and they see just how quickly they can get them to the circuit. Obviously, it depends on the complexity of the parts and how long it takes to design and manufacture. Certainly in terms of the aero there is a lot of evolution through the season and the car at the end of the year will be a couple of seconds quicker than the one that started the season as aerodynamically things get a lot more developed and tuned as the year progresses and you improve your understanding.’

Renault arrived in Spain with new parts on their front wing, bargeboard and floor. ‘As the first European round, Barcelona does offer a good opportunity to bring a number of updates to the car,’ highlights Nick Chester, Chassis Technical Director at Renault F1. ‘Most other teams will do the same, but we have a number of reasonable upgrades that are positive. At this stage there is a development race going on between the teams, but we will keep pushing hard to get the best from it each weekend.’

In addition to the new aero parts, Renault have also incorporated a few mechanical tweaks in an attempt to improve the balance of the car.

Car balance and tyres are a particular challenge for the teams as they transition from Baku, which has the lowest energy input into the tyres, to Barcelona, which has the highest. This

Under the skin of the SF90. Ferrari brought their 2nd specification of PU to Spain as well as an upgraded lubricant from Shell two races ahead of schedule in an attempt to close the gap to the two Mercedes

The 2019 rules restrict the front brake duct inlet size and teams are now converging towards a teardrop shape as shown by the upgraded spec on the Racing Point RP19 (left) compared to an older version (right)

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FORMULA 1 – BARCELONA AERO UPGRADES

The parts we have are all out of date because we are updating the car so quickly now, we don’t have all the spares we want is mostly down to turns three and nine which subject the tyres to huge lateral forces, particularly for the front left which is why teams often see high levels of graining.

Furthermore, turn three is at the beginning of the lap, and so often the tyres are not up to temperature and if the driver pushes too hard, the surface of the tyre can be destroyed resulting in a significant lack of grip by the third sector of the track. The trick to Barcelona is managing the tyres through turn three and although this might sacrifice a tenth in sector one, drivers can gain more time in sector three by having their tyres in a much better condition.

‘Depending on the tyre temperature, track temperature and other conditions there is a case of managing the tyres around the lap,’ highlights Dave Robson, Senior Race Engineer at Williams.

‘I think that’s always the case here. Sector three is so sensitive to rear grip that there has to be some amount of preparing the tyres because there is so much lap time to be gained or lost there. Preparing the tyres is a constant battle.

Look at everyone’s garages just before the drivers go out everyone is doing different things, whether that means nobody truly understands or whether teams are just doing what suits their car, their driver and their plan for the out lap.’

The Mercedes mirrors were mounted from the chassis swooping over the top of the mirror, forming an aerofoil shaped ‘hat’

Back to back

To analyse the performance gains of all these new parts, teams usually only fit these updates to one of their two cars so that they can conduct a back to back test between the new and the old specification. They can then analyse the data on Friday night after second practice and establish if they should run with the updated package for the remainder of the weekend.

‘If we put two cars with the new spec and then we have an issue - is it the tyres or is it the new spec?’ says Steiner. ‘We will consciously have a back to back comparison not to confuse us more with the tyre issue, and then if all goes to plan we will convert the second car to the new package on Friday night, as we cannot change it over in the time between FP1 and FP2.’

The tyre issue that has been jeopardising Haas’ season so far is the fact that they cannot seem to get the tyres into the working window.

However, sometimes teams opt for the opposite strategy; running both drivers with the new updates. This was Racing Point’s plan for the first two practice sessions in Spain, although this didn’t quite pay off as the team had initially intended. With only a set of spares for the upgraded suspension, the damage caused by Lance Stroll’s crash in FP1 meant that he couldn’t run with the new bodywork in FP2, losing the opportunity to gain invaluable data on the new package. Luckily for Racing Point, the proximity

Just when you thought you couldn’t possibly incorporate any more winglets into an area, Haas has proved that you can!

of Spain meant that spares could be sent out and fitted in time for Saturday, which is one of the reasons why teams prefer to introduce these packages when the series returns to Europe.

‘Last year, [this situation] would have been much easier, because there wouldn’t have been an upgrade on the car to start with,’ smiles Andrew Green, Technical Director at Racing Point. ‘Do we have more spares now? Probably not but for a completely different reason than last year. The parts we have are all out of date because we are updating the car so quickly now,

12 www.racecar-engineering.com RACECAR ENGINEERING FORMULA 1 SUPPLEMENT

so we don’t have all the spares we want, but it’s for a completely different reason than last year.’

With the first stage in each car’s technical evolution now complete, teams will begin the next challenge of finding even more performance gains, ready to implement into the next major upgrade package which will come around the mid-point of the Formula 1 season.

As this development battle continues, we will start to see the grid converge and only then will we get an indication of the optimum design for these new 2019 regulations.

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FORMULA 1 PREVIEW – F1 S-DUCT

Seductive aero The F1 S-duct is a clever aerodynamic trick that has been on Formula 1 cars since 2012. However, the details of how it works can be easily misinterpreted so we spoke to F1 aerodynamicists to find out the real reason behind the S-duct.

By GEMMA HATTON

F

ormula 1 is embroiled in a battle to reduce the impact of aerodynamic devices, but the introduction of the S-duct in 2012 by Sauber, and now widely adopted, goes to show how far the understanding of aerodynamics has come since. Much of the reasoning behind the device has been misrepresented, so at pre-season Formula 1 testing, Racecar Engineering asked the question of the leading engineers; what is the S-duct for, and what does it achieve?

Whenever air flows over a surface, it loses energy, which causes the flow to slow down and become turbulent. Therefore, once the flow has travelled over the elements in the front wing, it becomes ‘dirty’. In particular the gap between the underside of the nose, the upper surface of the front wing and the inner faces of the front wing pillars can cause an expanding tube of turbulent air. Add to this the fact that the air hitting the top corners of the nose can also accelerate round and roll

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underneath, and overall, the airflow under the nose can become extremely turbulent. This flow not only feeds the main turning vanes but also the leading edge of the underfloor.

Therefore, the cleaner the teams can get this airflow, the more performance they can extract from the other aero devices rearwards of the nose such as the turning vanes, bargeboards, underfloor and the diffuser.

‘The airflow under the nose is ‘dirty’ which means it is a slower speed flow that has been

Sciencedirect.com

The S-duct ingests ‘dirty’ airflow from under the nose via small NACA inlets (blue arrows) and distributes this flow into the cockpit via an outlet at the bridge of the nose (green arrows). Here, the turbulent airflow has less of a negative effect on the overall aerodynamics, compared to flowing onto the turning vanes and the underfloor.

The geometry of the NACA duct is essential in order to achieve the necessary vortices which help to ingest air, even disrupted flow, efficiently

worked by the presence of the nose and the front wing,’ explains Arron Melvin, Principal Aerodynamicist at Haas F1 Team. ‘To be legal, it is necessary to have certain nose volumes and inevitably there is a boundary layer growth due to the front wing and nose expansions. You can also get acceleration around the shoulder of the nose which leads to a high curvature flow.’

When air flows over an object, the molecules closest to the surface slow down, which then causes the molecules just above

them to slow down also. As the air moves away from the surface, the molecules gradually increase in speed up to the speed of the main flow. This thin layer of fluid where the velocity increases from zero at the surface to the free stream velocity is called the boundary layer, and its thickness depends on the viscosity of the fluid and the characteristics of the surface that it is travelling over.

‘We have introduced an S-duct for the first time this year and essentially we ingest this

dirty flow from under the nose through two pairs of NACA ducts and then release this flow on top of the chassis, rather than letting it travel underneath the car,’ says Melvin. ‘If we let it go underneath the car, the lower speed flow would arrive at the main turning vane, whereas now it goes through the inlets, into the cockpit and over the sidepod and does less harm. It is very much about where to place loss.’

A NACA duct is a type of inlet which allows the air to be drawn in with high efficiency and

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FORMULA 1 PREVIEW – F1 S-DUCT

Simon McBeath & ANSYS

minimal drag. To achieve this, NACA ducts are usually placed parallel to the local airflow and in locations where the boundary layer is relatively thin. The theory is that the shape of these ducts encourage vortices to form, reducing static pressure and enhancing the efficiency of the flow through the inlet. As air flows towards the narrow end of the duct, it flows down the gentle slope and into the inlet.

But the air that approaches from outside the inlet has to flow over the edges which causes a vortex. This results in the formation of two counter-rotating longitudinal vortices which then induce more air to flow down the duct.

S-duct outlet

Simon McBeath & ANSYS

An area of low static pressure can be seen at the edges of the duct (blue) as the rolling vortex is formed.

The two longitudinal vortices along the edges of the NACA duct induce more air into the inlet, as demonstrated by the yellow sections of the streamlines as they decrease in velocity.

Quite often the S-duct outlet at the bridge of the nose is misinterpreted as a device to help avoid flow separation due to the angle change from the steep nose to the flatter monocoque.

However, this outlet is simply about extracting the dirty airflow to a place where it will do the least damage to the car’s aero performance.

‘It’s a clear but ultimately relatively subtle technology and for a small team such as Haas, we had to be sure of the benefit to justify the additional costs,’ says Melvin. ‘The nose is more complicated to design and slightly heavier – it is an aerodynamic vs structural trade-off.’

This design relates to the fact that the air has to be channelled through the nose, up to the outlet. But these channels have to be incorporated in such a way that the nose retains its structural requirements to pass the FIA crash tests. This is the most likely reason behind why not all teams have adopted this technology. As mentioned above, this is the first year that Haas are running with an S-duct, and from pre-season testing, McLaren, Sauber and Racing Point opted to run without it.

However, its effectiveness may prove to be alluring for the teams this season.

The shape of these ducts enhances the efficiency of the airflow

There are a variety of designs for the S-duct outlet as shown here on the Mercedes W10 (left) and the Haas VF-19 (right) seen in pre-season testing in Barcelona 16 www.racecar-engineering.com RACECAR ENGINEERING FORMULA 1 SUPPLEMENT

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TECHNOLOGY – AERODYNAMICS

Lifting the skirts on ground effect

The Lotus 79 kick-started the ground effect revolution in Formula 1 following its dominant performance in 1978. It was also a very nice looking racecar

Modern Formula 1 aerodynamics are notoriously complicated but was it really far simpler 40 years ago? We take the CFD time machine back to the age of ground effects to find out

By SIMON MCBEATH

T

hey say that all race fans have favourite periods of racecar design.

This may have something to do with the cars one grew up watching. It may be down to aesthetics. Or it may be because of fascination with the engineering.

But one thing is certain, racecars are a lot more complicated now than they once were.

Pre-aerodynamic aids (effectively pre-1967 for single seaters) F1 cars were perhaps as simple as they could be – you might use the word pure instead of simple. However, once F1 engineers got a grip (no pun intended) on the benefits that aerodynamics and specifically downforce could bring there was no going back.

It might also be argued that the appearance of ground effect and its successful application to racecars in the late ‘70s and early ‘80s produced another pure concept. Thanks largely to the work of a small group working for Peter Wright, this magazine’s technical consultant who was then in charge of the wind tunnel programme at Team Lotus, beautifully integrated aerodynamic packages that exploited a large proportion of the plan area of the cars with an elegantly simple yet highly potent principle became the norm for a few years. But the reader would be correct if they were sensing writer bias here, so to be totally upfront about this, was there ever a more beautiful Formula 1 car than the

18 www.racecar-engineering.com RACECAR ENGINEERING FORMULA 1 SUPPLEMENT

JPS-liveried Lotus 79, or one that had cleaner lines than the Williams FW07?

The chance, then, to do some CFD on a CAD model of a 1982 ground effect F1 car (which for now must remain anonymous in deference to the owner’s wishes) was a great opportunity not only to examine how the aerodynamics on cars of that era functioned, but also to study what happened when things went wrong.

Sliding skirts along the outer, bottom edge of the sidepods (which had downforce-inducing profiled undersides) were originally the key to maximising the underbody’s downforce contribution. The objective was obviously to keep the spring-loaded skirts in full contact

Above and right: Wind tunnel models of the Lotus 79 with the skirt visible at the lower edge of the sidepod

Sliding skirts along the outer, bottom edge of the sidepods were originally the key to maximising the underbody’s downforce contribution with the ground at all times, but as history relates they didn’t always slide up and down as designed. Sometimes a jammed skirt would see a car leave the race track at a tangent to the intended curve, on occasion with disastrous results. The high loads generated also brought related engineering challenges, such as the need for improved brakes and beefed up chassis and suspension. So there were major issues surrounding these skirted cars.

However, when the skirts were in full and consistent ground contact the cornering and braking power of these Formula 1 cars was impressive, and the step forward in lap time performance was very significant.

The questions

So how did skirted ground effect work? What happened when the skirts jammed? And what happened (aerodynamically) when the regulators attempted to enforce a minimum skirt to ground gap in Formula1 in 1981?

First, let’s take a look at the aerodynamic performance of ground effect F1 cars from that period (they were banned at the end of 1982 and flat bottoms between the axle lines on Formula 1 cars became the norm). Our model looks to be representative for this purpose thanks to some in-period supporting data.

Table 1 highlights the key parameters derived from our baseline CFD run as coefficients, with comparison with some figures from a 1983 technical paper by Peter Wright at the same ride height and with skirts also in full contact (the data has been adjusted to represent notionally similar frontal areas). As can be seen the coefficients agree quite well between those derived in CFD for this article and the typical data published by Wright, which was obtained in the 5ft x 4ft Donald Campbell tunnel at Imperial College, London, on 25 per cent scale models of unspecified Lotus cars between 1978 and 1982 (Types 78, 79 and 91 were mentioned). Such agreement between

Table 1: The coefficients on our ground effect F1 model compared to Team Lotus-based data 1982 CFD model Lotus F1 ¼ scale

CD

-CL

-L/D

1.197 1.111

3.821 3.710

3.192 3.340

the data from different cars using different simulation methods, both of which had or have their individual shortcomings, provides confidence that the qualitative effects we’re going to focus on here have a sound basis.

CFD can do so much more than just enable the calculation of forces and trends though.

Not only does it enable us to break down the total forces into the respective contributions of each major part of the car, it also allows us to visualise the pressures and flows around the model, and easily to examine a few ‘what if’ scenarios, such as ‘what if the skirts jam?’

Once our model had achieved a satisfactory front to rear downforce balance, this then

RACECAR ENGINEERING FORMULA 1 SUPPLEMENT www.racecar-engineering.com 19

TECHNOLOGY – AERODYNAMICS Illustrations (S. McBeath/ANSYS unless otherwise stated)

enabled the distribution of the forces to be calculated. The dual-element rear wing featured a fairly flat, modestly cambered main element and a medium-steep flap angle, while the front wing was run at a shallow angle. This was common practice in period if front wings were needed. Sometimes cars would be run with no front wing, although one suspects this would probably be in circumstances that required lower drag, hence lower rear wing angles, hence the front wing could be dispensed with to maintain the aerodynamic balance.

Then and now

Figure 1 shows the drag contributions of the major components of our model alongside similar data from our article in V26N12, which (along with V27N1) featured a model created to the 2017 F1 regulations by Miqdad Ali of Dynamic Flow Solutions, used here as indicative of the numbers on recent Formula 1 cars.

The 1982 car’s body created a much greater proportion of the drag than was the case with the 2017 model, and given that the body width behind the front wheels has remained constant at 1400mm since then, this in part shows significant progress on drag reduction of the main body (which includes the upper and lower surfaces in this context), although it must also be related to the lower proportion of total downforce generated by the body. The 1982 car’s bigger wheels, unsurprisingly, were also bigger drag contributors, but its wings made smaller contributions, especially the front but even the rear wing made proportionately less drag than that of the 2017 car.

Figure 2 shows the downforce contributions of the same component groups, and the contrasts between the 1982 and 2017 models were even starker. The bigger wheels on the older car generated more lift, partly because of their greater width but also in the case of the rear wheels because the long sidepod and the presence of the side skirt forced more flow over the rear tyres. The wings generated less downforce on the older car, commensurate with the lower wing drag contributions highlighted above. But the biggest contrast was in the downforce contributions of the car body; when its skirts were in full contact over 95 per cent of the 1982 car’s total downforce came from the body compared to around 47 per cent on the 2017 car. In passing it ought to be said that the 2017 model (with no skirts of course) achieved somewhat higher total downforce than our baseline 1982 model for a not dissimilar drag level, highlighting 37 years of steady evolution in racecar aerodynamics to where we are today, for better or worse.

In order to maintain our test subject’s anonymity we are restricted to non-identifying views such as the underside, but no matter because this is where most of the interest occurred. Figure 3 shows the pressure distribution on our 1982 model’s lower

Figure 1: Drag contributions of the major components of our 1982 ground effect model compared to 2017 rules F1 model

Figure 2: This shows the contributions to downforce and lift from all the major car components for our two F1 models

Figure 3: Pressure distribution on the underside shows where most of the downforce accrued on the 1982 skirted car

When the skirts were in full and consistent ground contact the cornering and braking power of these cars was very impressive

20 www.racecar-engineering.com RACECAR ENGINEERING FORMULA 1 SUPPLEMENT

Figure 4: The streamlines show a fast, clean flow through the underbody, with the front wheel wakes entirely outboard

Figure 5: The effect of skirt gap on the downforce, as reported by Peter Wright on quarter-scale Lotus models in 1983

surfaces and it is immediately clear where the low pressure areas were generated. The front wing, which featured an end-plate reaching the ground to simulate a fixed skirt, exhibited relatively mild suction. The rear wing generated moderate suction, with variations across its span thanks to the wake of the driver, cockpit and roll hoop as well as those interesting flows coming up and over the rear tyres. But it’s easy to see how the main underbody generated the vast majority of the car’s downforce, since this is where the biggest pressure reduction was, and it was spread over a large plan area. The suction was concentrated in the forward underbody, hence only a small front wing (at most) was needed to balance the car. It’s also interesting to note that although it was the tunnels either side of the chassis that did the work, the pressure reduction they induced extended right across the underside of the central chassis too.

In Figure 4 streamlines have been initiated on a horizontal plane 50mm above ground level to show the flow velocities below the car. Note first that the ‘low power’ front wing created no apparent inwash or outwash component. The positioning of the tunnel entrances was such that only clean flow converged between the front wheels and entered the underbody while the dirty front wheel wake remained entirely outboard. The side skirts then ensured that no influx from the sides into the underbody was possible, and the accelerated flow in the forward underbody was virtually two-dimensional, remaining at high velocity (and therefore at low pressure) right along the flat throat region before then slowing down in the tunnel diffusers. Because of the side skirts, sideways influx only started at the rear of the sidepods, in line with the front of the rear tyres, and aft of this some of the rear wheel wake was drawn into the flow, issues which would have greater significance on subsequent skirt-less flat bottom Formula 1 layouts with aft-mounted diffusers, such as those we see today.

Skirting issues

Figure 6: Having no skirt (lower half) drastically altered pressure distribution on the underside. Full skirt is upper half

Not only had the suction in the underbody throat been all but lost, but there was also slight positive pressure about halfway along the tunnels

Two different scenarios of skirt malfunction could be envisaged; firstly, the simple case of a horizontal gap beneath the skirt, as if it jammed up but remained parallel to the ground; and secondly, the case of the skirt being jammed at an angle, either front-up or rear-up. Taking the horizontal skirt gap first, Figure 5 shows the reduction in downforce that Wright reported on the quarter-scale Lotus models in 1983.

Our 1982 model also showed rapidly declining downforce in this same scenario, although drag altered very little with skirt gap, aspects verified in real-world straightline track testing.

Visualising how these big downforce losses occurred is very revealing. Figure 6 shows the surface pressures on the CFD model’s underside with no skirt at all in the lower half of image compared to the fully skirted case. Not only had the suction in the underbody throat been

RACECAR ENGINEERING FORMULA 1 SUPPLEMENT www.racecar-engineering.com 21

TECHNOLOGY – AERODYNAMICS all but lost, but there was also slight positive pressure about halfway along the tunnels. Over such a large plan area this increase in pressure represents a huge loss of downforce. Recall that in 1981 the FIA temporarily banned side skirts and mandated a 6cm minimum ground clearance; it is perhaps no wonder that the teams responded with some frankly ridiculous ways of lowering the cars after their static ride height checks in order to bridge the gap along the bottom outer edge of the sidepods.

Figure 7 shows the streamlines again projected on a horizontal plane level with the underside, and by comparing with Figure 4 the very different flow regime is apparent. Not only did the removal of the skirt enable large scale inflow from the sides that now preferentially filled the tunnels, but it can also be seen that in the first third of the tunnel the streamlines actually flowed outboard of the edge of the sidepod. This was, no doubt, in response to the tunnels filling from the sides further downstream and to the obviously related slight positive pressure halfway along the tunnels mentioned above that all contributed to a much reduced mean velocity through the throat. The tunnels did still generate some downforce, at the inlet and also where the vortex that spun off the bottom edge of the sidepod created a drop in pressure in the diffuser.

Figure 7: Removing the skirts significantly altered the flows under the racecar too. Compare this image with Figure 4

Wing effects

The keen-eyed reader will have also noticed in Figure 6 that the rear wing appeared to show increased suction on its underside in the model with no skirt compared to the fully skirted case.

Indeed, there was a trend in the results that saw increasing rear wing downforce with increasing skirt gap, and the wing generated 35 per cent more downforce with no skirt than with the full skirt. What caused this effect? Contrast the predominant paths of the front wheel wake in Figures 8 and 9. In Figure 8 it is clear that the full skirt prevented the front wheel wake from getting under the car, which in turn saw it turn upwards and over the rear upper edge of the sidepod ahead of the rear wheel. From here it entered and adversely affected the flow field of the rear wing, reducing the wing’s downforce.

In Figure 9, the absence of the skirt allowed most of the front wheel wake to pass into the underbody and much less (though still some) of it went upwards to affect the rear wing.

So increasing the skirt gap or removing the skirt entirely not only drastically reduced the forward-biased downforce of the underbody but it also increased the downforce of the rear wing. This contributed to further rearwards shifting of the overall centre of pressure that the massive loss of forward underbody downforce had already created. As a related side note, some of the cars around this time had a raised fence along the upper, rear edge of the sidepod and from what we have seen from this study this fence must have been to

Figure 8: With full skirt the front wheel wake couldn’t enter the underbody but it had a negative effect on the rear wing

Figure 9: With the skirt removed the front wheel wake entered the underbody, not encountering the rear wing so much

It seems very clear then that any gap under the car’s skirt was quite a bad thing because so much of the downforce was then lost

22 www.racecar-engineering.com RACECAR ENGINEERING FORMULA 1 SUPPLEMENT

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TECHNOLOGY – AERODYNAMICS

Figure 10: This is the underside pressure distribution resulting from a front-up skirt jam

Figure 11: The underside pressure distribution that is the result of a rear-up skirt jam

Skirts had their issues, but whether they could have ever been made reliable became academic when flat undersides were mandated in 1983 steer the front wheel wake away from the rear wing when full skirts were deployed.

It seems very clear then that any gap under the skirt was a bad thing because so much downforce was lost. What then would have been

the effect of a skirt jamming up at the front or the rear? Two cases were run, one with the gap ranging from 45mm at the front to 10mm at the rear, which we shall call a ‘front-up jam’, the other ranging from 10mm at the front to 45mm at the

Figure 12: Streamlines show the wake of our 1982 skirted ground effect Formula 1 model; note inwash near ground level

Figure 13: Wake on a plane 50mm above ground level narrowed significantly at just one or two car lengths behind model 24 www.racecar-engineering.com RACECAR ENGINEERING FORMULA 1 SUPPLEMENT

rear, a ‘rear-up jam’. Again there was minimal effect on drag but the downforce losses were substantial in both cases. The more likely to occur front-up jam saw very slightly less overall downforce lost than the rear-up case, the latter showing losses not far short of the no skirt case.

The visualisation of the front-up jam in Figure 10 shows that the surface pressures on the car’s underbody were generally lower than in the no skirt case as shown in the lower half of Figure 6, with an intensification of the vortexinduced suction ahead of the narrowing skirt gap. Hence the downforce loss in this instance, while still drastic, was not as much as in the no skirt case. Figure 11, showing the underbody pressures in the rear-up jam case was more akin to the no skirt case, although the presence of the tilted skirt did cause some intensification of the vortex that added a little more suction to the forward diffuser region. In essence then these jammed skirt scenarios were really just variations of the no skirt case given the large downforce losses and balance shifts.

Future ground effect

Skirts certainly had their issues then, but whether they could ever have been made reliable became academic when flat undersides were mandated in 1983, ultimately leading to the rules we have now in 2019.

It has been said that ground effect cars were able to run close enough to allow drivers to be able to race each other, and Figures 12 and 13 show the wake in two different ways, revealing central upwash that seemed to entrain much of the rear wheel wake, and relatively clean inwash behind the car. Figure 13 implies that at just one to two car lengths behind the car the wake at underbody level was not too badly disturbed, possibly explaining how the cars could run close. Maybe these, more than the 37-yearold qualities of ground effect cars, are among the current objectives of the FIA’s research highlighted in the April issue of Racecar?

Skirts on a Group C sportscar Table 2: The effects of fitting skirts on a Group C Mazda 787B model No skirt Outer skirt Inner skirt

CD

-CL

-L/D

0.426 0.384 0.368

1.909 1.150 0.995

4.478 2.990 2.704

Figure 14: Mazda 787B Group C model with skirt fitted.

The car, which famously won Le Mans in 1991, never raced with skirts in period as these had been banned

S

kirts had long been banned when Group C produced probably the highest downforce levels seen on mainstream racecars. But would they have enabled Group C prototypes to have generated even more downforce? Readers may recall that in V28N10 (October 2018) we examined a model of a Mazda 787B replica in 1991 Le Mans-winning trim. By kind permission of project owner Mark Peters the model has been used again to examine the effects of skirts.

Skirts were first attached along the outer edges of the car’s floor (Figure 14), then moved inboard by 350mm. The results are compared in Table 2 to the best run from our previous article, which featured no skirt.

It is immediately apparent that this simplistic approach has caused very significant reductions in aerodynamic performance. Drag may have reduced (by 10 per cent and 14 per cent respectively) but downforce reduced by 40 per cent and 48 per cent compared to the skirtless model. Why was this?

Figure 15 shows streamlines under the car in the no skirt case. The diffuser tunnels were being filled partly by flow from the front and partly by flow from the sides. The latter not only created suction under the outer flat underside, it was also being spun into large vortices in the tunnels helping to maintain attached flow, which in turn helped to pull high mass flow through the entire system, resulting in high underbody downforce.

As soon as either skirt was attached the lateral influx was cut off and the diffusers stalled, leading to the reductions in downforce.

This is yet another example of how a device that works on one type of racecar does not necessarily work on another.

Figure 15: With no skirt the tunnels were partly filled by flow from sides, improving the underbody suction

Figure 16: This shows how the outer skirt cut off all the lateral influx which meant the diffusers stalled

Figure 17: Inner skirt also cut off most of flow from sides, causing even greater downforce reduction RACECAR ENGINEERING FORMULA 1 SUPPLEMENT www.racecar-engineering.com 25

FORMULA 1 – 2021 TYRE DEVELOPMENT

Size matters Pirelli won the tender to supply F1 through its next regulation phase, but how will the Italian firm develop this new 18 inch rubber for 2021?

By GEMMA HATTON

26 www.racecar-engineering.com RACECAR ENGINEERING FORMULA 1 SUPPLEMENT

As well as potentially introducing new materials to improve the current range of compounds for next year, Pirelli also has the monumental challenge of developing the 2021 tyre range The 2021 season will see a dramatic switch from the current 13 inch tyres to 18 inch low profile tyres and larger wheels, with a potential ban on tyre blankets too

W

ith the 2019 season not quite living up to everyone’s hopes of ‘shaking up the F1 grid’, there is a whiff of despair in Formula 1 with the realisation that the next set of rule changes are still two years away. However, in preparation for the 2021 rules that are really set to be revolutionary, you’ll be pleased to know that there is plenty of fascinating engineering going on in the meantime.

One of the major changes for 2021 is the rims and tyres which will go from their current 13 inch diameter to 18 inch diameter. This will require a complete overhaul of the current tyre concept used in Formula 1, and consequently significant testing and development time. It also has a knock-on effect for the teams, as they will have to redesign the suspension and aerodynamics whilst learning a whole new tyre behaviour in order to remain competitive.

Two-step

To help Pirelli prepare for this challenge, the FIA announced at the Spanish Grand Prix in 2019 that Formula 2 will switch to 18 inch tyres in 2020, a year earlier than F1. ‘The FIA Formula 2 Championship marks the final step in a young drivers’ careers as they strive to achieve a place in Formula 1,’ says Stefano Domenicali, President of the FIA Single-Seater Commission. ‘And with these plans to introduce, test and develop a new tyre profile next season ahead of its introduction into F1, we are showing that Formula 2 is not only the place to prove the top driving talent, but also the latest technologies.’

Pirelli already supply 18 inch tyres to several GT and Touring Car championships, but an 18 inch single seater tyre is a new challenge.

‘Formula 2 is the closest championship in terms of performance to F1 so we can for sure learn something and it is a good opportunity to get some experience form our side,’ highlights Mario Isola, Head of F1 and Car Racing at Pirelli.

‘We cannot compare the aero of an F2 car to the aero of an F1 car. The stress and energy acting on the tyres of an F2 car is much lower than in F1, and this delta has become a lot bigger. Before 2017, a very quick GP2 car was more or less in last position of the F1 grid, but in 2017 where F1 cars stepped up by five or six seconds per lap, we now have a delta that is sometimes up to 12 seconds, so the gap between F2 and F1 is bigger. Also, F2 is still on the narrower size. So, we will develop a bespoke F1 tyre with the mule cars that have representative performance [to F1]. The fact RACECAR ENGINEERING FORMULA 1 SUPPLEMENT www.racecar-engineering.com 27

FORMULA 1 – 2021 TYRE DEVELOPMENT

Before 2017, a very quick GP2 car was more or less in last position of the F1 grid, but we now have a delta that is sometimes up to 12 seconds

To prove that F2 is not just a platform for developing F1 drivers, but also F1 technologies, it was announced at the Spanish Grand Prix that F2 will switch to 18 inch tyres in 2020. This will help Pirelli prepare for F1 2021

that we are supplying F2 with 18 inch next year will be helpful because it means we can analyse the tyre footprint, pressure distribution [across the contact patch], heat generation and have some experience of 18 inch single seater tyres.’

Last tango

The additional benefit this brings to F2 drivers is that they will have an entire season’s experience on 18 inch rubber. Therefore, they can adapt their driving styles to suit the characteristics of these new larger tyres; setting them up nicely for a jump into F1 in 2021. With pure speed no longer the key performance differentiator in modern F1, being able to extract the maximum performance out of the tyres whilst nurturing them to the end of the race is now an essential skill to be a successful driver.

This is proven by the pace of this year’s rookies, with Franz Tost, Team Principal at Scuderia Toro Rosso attributing Alex Albon’s success this season so far to the fact that he ‘understands how to use the tyres in the best possible way…Alex could become the driver surprise of the year.’

To be ready for next year’s F2 season, Pirelli will have to turn around a tyre development programme in a very short space of time.

However, development has already started as the first shake-down was completed in early May at the Autodromo del Mugello. Italy, with a modified F2 single seater. Pirelli will continue an intensive testing programme which could consist of up to 10 test sessions this year, in order to be ready for 2020.

they also have the monumental challenge of developing the 2021 tyre range.

‘With an 18 inch tyre you have less volume of air inside it, so you have a different pressure increase which modifies the footprint, which we have to consider,’ highlights Isola. ‘The tyre is a lot more reactive, and more precise and teams will need to redesign the suspension because the sidewall of the tyre is a lot less compared to now. We are also increasing the external diameter, so this will influence the aerodynamics and don’t forget that the interaction between the brake and the rim is very important, not only for heat exchange but also for the airflows that are in this area.’

Weight also has to be taken into consideration. The weight of the tyre will most likely stay the same, or be slightly heavier as the majority of a tyre’s weight is within the tread. However, the rim will certainly be heavier, potentially around 2kg heavier according to Isola. That means 8kg of total weight added to the car, which is a huge change.

But it is not just the increased size that Pirelli will have to cope with; there is also talk of a potential ban on tyre blankets. Currently, the rubber is so temperature sensitive that if drivers leave their pit with a tyre that is a few degrees

below optimum, it not only takes longer to warm up, but in some cases it never reaches the working window at all. Therefore, designing a tyre that can cope with starting at 30degC without blankets, rather than 100degC (front) and 80degC (rear) with tyre blankets will likely require a completely new design of both the compound and construction.

Test match

To manage this, Pirelli will also be completing an extensive F1 testing programme, starting in September this year and continuing through 2020. This year, three two-day test sessions will be run with mule cars which will be modified to accommodate 18 inch rims and tyres. All teams were offered the opportunity to take part, but only Mercedes, McLaren and Renault accepted.

Next year, Pirelli want to run another 25 days of mule car testing and will once again open up the opportunity for the entire grid to take part.

Rubber necking

In parallel with the F2 testing programme, Pirelli also need to keep their eye on F1’s tyre development too. As well as potentially introducing new materials to improve the current range of compounds for next year, 28 www.racecar-engineering.com RACECAR ENGINEERING FORMULA 1 SUPPLEMENT

The baseline model used for developing the 2021 car.

Pirelli say that because the 2021 rules are so different, teams that don’t participate in the mule car testing should not be disadvantaged. We’re not so sure!

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FORMULA 1 – 2021 TYRE DEVELOPMENT

??? ???

18 inch tyres are more reactive and precise in terms of handling compared to the current 13 inch tyres. There is also a smaller volume of air which changes the rate of pressure increase and therefore the contact patch

A mule car is an F1 car that has been modified to suit the specific requirements of the test tyres. ‘Current cars’ will be used for this programme which means cars from 2018 and 2019. Similar testing was conducted in 2016, in preparation for the wider tyres introduced in 2017, but for that ‘previous’ cars were used (two years or older) so as not to give the participating teams an advantage over the teams that weren’t involved. So, in an era with such heavily restricted track running surely testing a current spec-car, even though it has been modified, will benefit those teams involved?

‘Not really,’ concludes Isola. ‘I believe that the 2021 cars will change a lot so it’s not really an advantage. If you compare 2017 to 2018 and 2019, we have had quite a stable set of regulations. OK, they have changed the wings [this year] but considering the changes scheduled for 2021, the changes over the last three years are very minor compared to what we can expect for 2021.’

Resources and time have been the main reasons why most teams opted out of this year’s mule car testing, as is the promise to share the gathered data. ‘It was our own choice not to participate, being short on time and resources for the programme, so we decided not to test in 2019 but are preparing ourselves to do it in 2020,’ explains Mattia Binotto, Team Principal at Ferrari. ‘Will this be a disadvantage? We

To suit the 18 inch wheels, teams will have to redesign their suspension as there is less sidewall believe that you cannot do everything and you need to meet your own priorities at some stage. Pirelli will share the data with all the teams and the output of the mule car testing so we’re certainly counting on that.’

‘If Mattia is short of resources to do the test, you can imagine that for us it’s not easy,’ concludes Frederic Vasseur, Team Principal at Alfa Romeo – which is a common theme throughout the smaller teams.

Cold turkeys

‘I think it was a disadvantage last time not doing it [the 2017 mule car testing],’ says Andrew Green, Technical Director at Racing Point. ‘Is it going to be a disadvantage next time doing it?

I don’t know. I hope not and I hope that they’re going to try and mitigate for the teams that don’t participate. It is a significant programme given the change in architecture that is required.

It’s not just the change in geometry but the change in characteristics with no blankets, it’s a big thing. The cost could be in the hundreds of thousands. We don’t have the capability to do it, but we’re happy to do the learning when the specification of the tyres has been finalised.’

30 www.racecar-engineering.com RACECAR ENGINEERING FORMULA 1 SUPPLEMENT

These mule car tests will be run under the same conditions as the current tyre tests.

Therefore, Pirelli will share the run plans, results and relevant data in an attempt to achieve sporting equity. However, to suit the 18 inch wheels, teams will have to redesign their suspension as there is less sidewall, and therefore less opportunity to use the tyre as part of the suspension system.

This change in spring effect, and the other changes that teams will have to make to these mule cars to simulate the expected aerodynamic performance of 2021 will be crucial in helping Pirelli achieve representative results. Despite the big regulation changes, which will essentially boil down to a different set of input loads that the suspension system will have to cope with, it seems highly likely that the teams developing the mule cars will gain an advantage running the 18 inch wheels, which could prove invaluable. Unfortunately, we will have to wait to find out this answer. Only when the number of teams taking part in the 2020 mule car testing is revealed, will we start to get an idea about how much of an advantage the teams think this could be for 2021.

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FORMULA 1 – 2021 REGULATIONS

A glimpse of the future The shape of Formula 1’s 2021 regulation package is beginning to emerge with all parties currently working on a base model codenamed ‘India’, a conventional open wheeler that will feature ground effect aerodynamics and a number of control parts. Racecar investigates

By SAM COLLINS

F

ormula 1 is to adopt a completely new technical rulebook in 2021, but until now all that has officially been revealed are some vague concept sketches and the announcement that 18 inch wheels fitted with low profile tyres will be used.

But there has been progress, and behind the scenes the FIA, the F1 Group and the teams have been collaboratively working to thrash out the details of the new technical regulations. At the time of writing that work is ongoing, but recent documentation has provided a lot more clarity on the overall shape of things to come.

Despite rumours of fighter jet style canopies and Le Mans Prototype inspired bodywork,

Formula 1 will remain an open cockpit, open wheel, single seater category, with most of the main elements of the current cars retained, albeit in modified form. We know this because a base model of a generic 2021 car has been created and supplied to the teams, and the latest iteration of it, called ‘India,’ offers a clear insight into the direction of the new rules.

Passage to India

The biggest change in terms of the aerodynamic package is the introduction of a fully ground effect floor complete with substantial tunnels and a number of underbody aerodynamic elements, while the cars will feature far more

32 www.racecar-engineering.com RACECAR ENGINEERING FORMULA 1 SUPPLEMENT

basic front wings (even compared to the 2019 package), low noses and an interesting double element rear wing with no end-plates. Outer wheel covers will also feature front and rear, reducing the drag but perhaps also creating a major challenge in terms of brake cooling.

In terms of the sidepods, the current trend of complex bargeboards and lowering the side impact structure for aerodynamic gain is unlikely to continue beyond 2020, with the India model not featuring bargeboards at all, and the low side impact structure approach seemingly ruled out with new, more sculpted, sidepod ducts.

Each team, if it wishes to, can get involved in the CFD development project using the India

The baseline ‘India’ model used for developing the 2021 regs. The cars will feature low noses, simple wings, no bargeboards and full ground effect floors. Note the small elements above the front wheels and the large diffuser at the rear

Formula 1 will remain an open cockpit, open wheel, single seater formula, with most of the main elements of the current cars retained

RACECAR ENGINEERING FORMULA 1 SUPPLEMENT www.racecar-engineering.com 33

FORMULA 1 – 2021 REGULATIONS

The India concept aims to keep the front wheel wake as narrow as possible and inboard of the car model and many have also already done work on the previous version codenamed ‘Hotel’. The teams can nominate a project to work on and a list of projects is circulated to all the teams, so that the work is spread and not repeated. Once the results have been processed they are shared with the FIA. CFD work on these projects is not covered by the current aerodynamic testing restrictions during two six week periods, the first of which concluded at the end of March 2019, with the second in May 2019.

Gearbox casings will remain the responsibility of the individual F1 teams but the transmission cassette will be a spec part

Wake up call

The India concept aims to keep the front wheel wake as narrow as possible and inboard of the car, achieving this by relying on a balance of vorticity either side of the contact patch.

However, reliance on this is not ideal as some conditions or minor design changes can result in an imbalance between the vortices and moving the wakes outboard, something that is known to be detrimental for any following car.

In documents circulated to the teams just before pre-season testing got underway in Barcelona, they were challenged to look at changing the front wing concept, in terms of width, height and end-plate design, to ensure that the front wheel wake will be properly managed. Front wheel arches and wheel pods are also being considered and could be retained ‘as long as the car maintains an open wheeled appearance’.

In the centre part of the car the India concept has a fully tunnelled floor with a single, large, locally generated vortex to provide downforce, but documents show that this is far from a completed concept and the teams have been asked to investigate this area further, and to get a better understanding of what influence it has on the wake of the car. Ideas like underfloor turning vanes and adjustable canard wings have all been suggested.

Meanwhile, at the rear of the India concept model the Formula 1 R&D group, headed by Nikolas Tombazis, Dominic Harlow and Jason Somerville, has developed a rear end system which could make it easier for Formula 1 cars to follow each other more closely. It is designed to ensure that the rear tyre wake is kept as narrow as possible and is drawn into the so-called ‘mushroom’ wake structure.

This mushroom structure is created by the

Drag reducing wheel covers, as seen here fitted to the 2006 Ferrari, could be a feature of Formula 1 cars from 2021

In an attempt to reduce costs there is a plan to introduce an increasing number of control parts upwashing cascade of the diffuser, low beam wing and a number of other small elements.

The diffuser is protected from undesirable flows entering from the side by end-plates on the rear brake duct winglets and other components creating a downwash between the diffuser wall and the rear brake duct. However, the vortex coming off the rear wheel can still enter the diffuser and reduce its performance.

This is something that the blown diffusers of a few years ago, in both Formula 1 and LMP1, were designed to prevent. Here the teams have been asked to counter this effect, and it

34 www.racecar-engineering.com RACECAR ENGINEERING FORMULA 1 SUPPLEMENT

potentially could see the return of the blown diffusers. Another task set for the teams to work on is to raise the mushroom higher to allow the cars to follow even more closely.

Transmission revamp

Details about the mechanical elements of the 2021 cars are also beginning to emerge, including the transmission. In an attempt to reduce costs there is a plan to introduce an increasing number of control parts, which will be used by all cars. One of which is the gear cluster. Currently teams work with a range of

BSc (Hons)

FORMULA 1 – 2021 REGULATIONS

The tender calls for a single spec cassette containing seven forward gears and one reverse, down one ratio from the current transmissions companies such as Ricardo, Xtrac and others on their clusters, but the FIA has now issued a tender for a single supplier for the 2021 season.

The tender calls for a single spec cassette containing seven forward gears and one reverse, down one ratio from the current transmissions. Gear ratios will be fixed across the field, while the differential will be a multi-plate, hydraulically controlled unit.

‘It is anticipated that the layout will be similar to current Formula 1 gearbox/final drive assemblies,’ the tender documentation states. ‘The exact layout definition will be part of the selected provider’s responsibility but it should be as close as practical to something all teams are happy with. It is believed that both single barrel and dual barrel arrangements are currently in use but it will be for the selected provider to select the layout they believe is best.’

In the tender it is recognised that the teams are likely to push the rear end packaging of their cars as hard as possible, and it calls for applicants to apply ‘significant effort’ to making the cassette as small as they can and as light as possible while meeting the required demands.

Those demands are not all that clearly defined, as in some areas the regulations are still a work in progress, but the new gearbox would

be expected to last around 5000km (roughly the distance covered in the Le Mans 24 Hours by an LMP1 car). While the power unit regulations remain unclear (see box out) the tender states that the input shaft speed is expected to be around 14 per cent higher than at present and that there will be a power increase over the current power units due to natural development, but also an upgraded MGU-K (with around 30kW more power).

With cost reduction a major aim of the 2021 rulebook the tender makes it clear that the new transmission internals will not need to utilise as much advanced machining as is common now. ‘Saving the last few grams can be replaced with more cost effective machining as this is a common part. As a guide, it is anticipated that the gearbox cassette will be around 1.5kg heavier than an equivalent cassette-style F1 gearbox today,’ the tender explains.

On the case

The perimeter of the spec transmission includes the complete oil system for the unit comprising tanks, pumps and scavenging systems in a self contained unit, with an outlet and inlet to and from an oil cooler. However, the tender does not cover the transmission casing and this will

remain the domain of the teams. Currently McLaren, Red Bull, Mercedes, Ferrari, Renault and Williams all design and utilise bespoke casings while the other four teams buy them in.

The input and output set-ups of the 2021 transmission are defined in the tender documents; ‘a team-specific input shaft will connect the engine-mounted clutch to the input of the gearbox cassette, which will provide the team with the ability to tune the torsional behaviour of their complete transmission system. The gearbox cassette end of the shaft will be defined by the selected provider and will include an appropriate spline drive and a short portion of shaft used for the FIA-defined torque sensor. Forward of the torque sensor portion, the design of the input shaft will be free,’ states the document. In terms of output the driveshafts will remain free though it is thought that the design of the inner end will be prescribed in the technical regulations. The new transmissions will be used from 2021 through to the end of the 2024 season.

Further details of the 2021 cars are expected to be revealed in the summer, after the second phase of the India concept CFD studies are completed in May, and the regs are likely to be approved towards the end of 2019.

Formula 1’s future power unit

F

or some time in Formula 1 a substantially new power unit rule book was expected to be introduced for the 2021 season. However, it now appears that this will now not happen after all, and that if there are any changes to be made then it seems likely they will be fairly minor.

‘I think Formula 1 has a role to play in powertrain development, but I think 2030 is where we should be looking,’ says F1’s chief technical officer Pat Symonds. ‘The current engine, may or may not have a mid-life facelift in 2021, and that will be with us until 2025. So the new engine will be mid-life by 2030.’

So 2025 is now the expected date for the introduction of the new power units, and it looks like these will be fundamentally different to what is in use today. ‘We will be looking at novel mechanical and chemical solutions,’ Symonds says. ‘We might be looking at two stroke cycles, split cycles, variable valve phasing, variable valve timing and lift, and variable compression ratio as well. We need to improve gas exchange, that means better turbochargers with a lot of extension of the maps, perhaps two stage turbocharging, variable geometry, things like that. More waste heat recovery is likely to feature, we are obviously using turbo compounding at the moment, but perhaps we could look at fuel reforming or organic Rankine cycle. There are reports that say the latter could improve fuel consumption by about 4.2 per cent.’

Formula 1 restricted combustion development somewhat when it limited component weights and compression ratios in order to close up the field, but in this area it is clear that substantial change can be expected in 2025. ‘In terms of combustion we are already using pre-chamber ignition and perhaps things like simultaneous ignition could come in,’ Symonds says. ‘We will also be looking at high peak firing pressures, though they are already very high at the moment, [and] gasoline compression ignition is very much on the horizon.

[Also], model based combustion control and multi mode control where we can use machine learning and AI to improve the timing.’

It seems certain that, with the wider automotive industry moving towards all new passenger cars becoming either fully or partially electrified within the next 10 to 15 years, Formula 1 will remain a hybrid formula. But the detail of that hybrid system is likely to change with the rest of the power unit.

‘On the hybrid side, we are probably going to quad voltage systems, where we are using 400 volt, with 600 volt for traction, a 48 volt system for ancillaries, a legacy 12 volt system and a 5 volt instrumentation system,’ Symonds says. ‘The 48 volt system will allow the auxiliaries to be used on demand, and I think anything with a load of over about 500 watts is certainly better running on the 48 volt system; an electric valve train, for example, you need about 800 watts per cylinder to run it.’

Small changes to the PUs are expected in 2021, and possibly a more powerful MGU-K

36 www.racecar-engineering.com RACECAR ENGINEERING FORMULA 1 SUPPLEMENT

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