Formula One car development blog

Pirelli escapes trouble with standing waves in tyres

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It was just 2 years ago when Pirelli attracted some negative publicity with tyre cuts at the same Spa-Francorchamps when on Friday and Saturday, images revealed considerable standing waves in the rear tyres of some cars. It's a known phenomenon, but the intensity of it at Spa even left some top engineers without explanations.

Perhaps the most obvious occurrence was the one on Lewis Hamilton's Mercedes F1 W08. As he exited the chicane and powered up onto the start finish straight, the car vibrated intensely for around 5 seconds. The vibrations were thanks to an unusual deformation of both rear tyres, even though Hamilton wasn't particularly hard on the kerbs. A bit later on in qualifying, the deformation broke off a rear wing element on Lance Stroll's Williams as well. The issue cost him a second run in Q1.

On Saturday evening, after Pirelli had asked teams to share data, so they could better analyse the issue, Williams' Paddy Lowe confirmed he didn't see such deformation before.

"We have often seen before a kind of standing wave in the sidewall, but in this case, we're seeing a standing wave on the tread with sort of a flat threepenny bit shape to it," he said. "I've never seen that before. It's a very high amount of energy in that."

Pirelli reported on Sunday morning the issue was of no real concern to them, with lab simulations showing no immediate issue with the tyres themselves. Mario Isola, Pirelli's motorsport chief, said they were still trying to understand the matter.

"It looks like we have this vibration just out of Turn 19 and Turn 1, so it is a specific point," he admitted, "it's not on all the circuit. But because it is the first time we see it so clearly, and maybe also the slow motion images were announcing a little bit this effect, when we see this, we want to understand it.

"We are checking with all the teams, because it's important to have feedback from them. They have not only the data, they look at the suspension, they look at the floor, they look at the wings, so they can give us more complete feedback. Obviously if you touch certain frequencies, then you can generate a failure."

Indeed, the rotational force exerted on the wheels, combined with high grip of the tyres creates flexing in the tyre walls. At a certain frequency - which depends partly on the tyre construction - flexural waves can form around the edge of the tyre. It appears that in this case at Spa, the energy in the waves was such that the tyre wall didn't normalise when completing a full rotation, resulting in the more than obvious shudder of the car itself.

It'll be interesting to see if Pirelli can discover and reveal a complete explanation, and if such behaviour will be seen again at Monza, where cars similarly accelerate hard out of slow corners.



Internals of Ferrari's 2014 water-to-air intercooler exposed

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Thanks to the bankrupty and public sale of some assets of the former Marussia F1 Team, we now get to take a very up-close look at some of the car's parts from 2014. Peter Bjorck for instance has bought a number of Ferrari engine parts, including the water-to-air intercooler and the unique butterfly wastegate from the Ferrari 059/3 engine as it ran during the 2014 season, the first year of the new hybrid turbo engines in F1.

In the below clip, Peter walks us through the intercooler, which sat in the engine's V. Air flew through it to cool it down before being guided towards the cylinder air intake plenums, one for each cylinder bank. Unpacking shows 16240 small water pipes in the aluminum intercooler.


Mercedes kicks off the development war

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The Spanish GP is usually the venue of the introduction of the first significant development packages of a season. This year, Red Bull was expected to launch a heavily upgraded car after its woeful start to this year’s campaign. The energy drink-owned team brought some aerodynamic changes to its challenger, but it was Mercedes that drew most of the attention to itself by a major front end aerodynamic update.

The biggest change visually is the car's narrow nose, which obviously had to undergo a separate crash test before it could be used on track.The narrower version means there is a well-marked transition at the front bulkhead, where the detachable nose cone meets the front end of the chassis. Under the nose section, there is a very elaborate turning vane, already nicknamed 'teddy cape', to manage the turbulent wake of the front wing.

The way Mercedes engineers are paying attention to the details is clearly showed how the camera mountings were updated for this race. The construction of those mountings, and the exact position of the camera hubs are tightly regulated, but Mercedes still found a way to create slender mountings that provide the least possible obstruction to airflow passing aside and just on top of the nose cone.

Similarly at the front, the brake ducts evolved, with a different 2-element winglet now present on the suspension support arm, along with a revised shape of the inlet fairing.

The car's floor also underwent considerable changes, with the barge board getting a similar upgrade to work together in front of the sidepod. Together, they manage the vortices coming off the front wing and attempt to cleanly direct airflow underneath and around the sidepods. The complexity with serrated extension has made it nearly impossibly for teams to introduce modified barge boards without also adapting the floor, as both are extremely dependent on each other.
For the Spanish GP, the bargeboards got even more sophisticated. Three vertical vanes are now placed on the horizontal plane of the bargeboards. There is no other bargeboard which is close to the Mercedes’ solution in terms of complexity and serration.

Further back, the floor also features an additional small vane directly ahead of the rear tyres to direct air away from the turbulent area. That section of the underfloor was already rather complex with nine cuts along the side-edge. And for another extra bit of downforce, Mercedes also added a monkey-seat after running the W08 without one so far.

Mercedes also worked on its engine. It brought an updated power unit to Barcelona. The upgrade is aimed to improve the reliability of the Mercedes W08 EQ Power+. It can, however, have an impact on the power as well since it can allow the drivers to use the power unit closer to its maximum for a longer period of time in race conditions. Both drivers got new internal combustion engines, turbochargers, MGU-H and MGU-K units which are all only their second of the season. However, Valtteri Bottas had to revert to its previous ICE before qualifying. He later blew that engine, which was used in the first four races of the season, during the race.

Still, that's not the end of the story. Having been overweight at the start of the season - partly due to an overweight gearbox - the team focused on shedding some of that. 3kg was reportedly shaved off with the Barcelona update. That's only part of the way however, as Hamilton admitted after the race he did not have a drink bottle onboard for weight saving.


Mercedes S-duct evolution

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While other teams have been busy copying Mercedes' S-duct inlets in the nose cone, the championship team itself was busy further developing its own device. The team have certainly taken inspiration from McLaren's solution of 2016, with an outlet ahead of the kink in the nose cone, and split up by the fairing around the pitot tube.

An image taken today by f1today also shows the clear evolution that Mercedes have done, making the outlet clearly a lot larger than it was on the F1 W07. On last year's car, the slot exit was located aft of the pitot tube, and quite far behind the front bulkhead as well. This year, the outlet was moved considerably further forward. This is particularly noticeable when you take into account that the pitot tube has not moved relative to the front bulkhead.

Today's image also shows how the front wishbones connect to the monocoque, with the upper ones connecting to the chassis at the highest possible point. It appears as such that the S-duct exit was made as wide as was possible while ensuring rigidity for the suspension. The steering arm enters the chassis ahead of the front bulkhead, with the steering rack also screwed onto the chassis, ahead of the front bulkhead, but protected inside a carbon fibre housing. The latter should also make a quick nose cone change easier.


Mercedes trials chimney via dorsal fin

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The Mercedes F1 W08 was seen in testing at Barcelona with a shark fin that features an opening on top.

This hot air outlet is obviously a trade-off with openings at the back of the car, but may be an interesting development route now that the rear wing is now placed lower, putting it quite a bit below the exit stream of the chimney. In addition, by opening up this cooling outlet up there, Mercedes is able to cut down on venting at the rear of the car, allowing cleaner flow underneath the rear wing and on top of the diffuser.

This particular type of cooling outlet is usually nicknamed chimney due its shape being very similar to an actual smoke shaft. It is not a novel type of solution in F1 as it dates back to the early 2000's.

Back then, cars featured these outlets on the sidepods. The benefit was/is a much more aerodynamically efficient solution than regular openings for cooling, with the turbulent and low energy air coming out of it being vented high above and away from the aerodynamic platforms.

They got effectively banned with the regulation changes of 2009 which regulated a minimum radius of the sidepod's bodywork. Sauber later found a way to circumvent this by integrating one in the sidepod turning vane for its Sauber C30 back in 2011, but it was eventually discarded due to the additional pipework that was necessary inside the sidepods, making these more bulky in critical areas as well.

As our previous article mentioned however, it remains to be seen if the solution will be allowed for long. If the FIA bans shark fins based on safety grounds, than this avenue will be closed off as well.


2017 design trends: adoption of the S-duct

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Having been tried, used and developed by several teams in recent history, 2017 finally looks to become the year in which (nearly) all teams add some form of S-duct on their cars. It is a solution which was first pioneered by Ferrari back in 2008. Back then, it was aimed at improving their airflow underneath the nose cone at a time when front wing development was possible in the central section of the wing as well.

The major regulation changes of 2009 removed the possibility for Ferrari's nose ducting. A further restriction came after Mercedes used the front wing stalling double-DRS system. The FIA then stipulated that apertures more than 150mm ahead of the front wheel centreline could only be for driver cooling.

Still, that enabled Sauber and Red Bull, and later also McLaren and Force India to use the commonly known S-ducts, featuring apertures underneath the nose cone and guiding air through an S-shaped duct through the nose to exit on the upper side, usually just ahead of the front bulkhead.

In 2016, Mercedes and Toro Rosso implemented further improvements to the system. By carefully designing small inlets left and right of the underside of the nose cone, inlets were made possible within the scope of the regulations. This enabled much more straightforward internal ducting, and a more beneficial inlet location. The result is that this year, Toro Rosso modified its inlet design to resemble that of the Mercedes F1 W07 and Ferrari, McLaren and Williams following the same route. Red Bull Racing and Renault seem to have stuck with apertures less than 150mm ahead of the front wheel centreline.

S-duct designs on McLaren MCL32 and Renault RS17

On the outlet side, teams seems to be following a route initiated by McLaren in 2015, where the air exited ahead of the transition from the steep upper nose profile to the flat upper side of the monocoque. Toro Rosso and Mercedes notably chose this route, and also split the outlet by putting the pitot tube in the middle. McLaren interestingly chose to the move the pitot tube out of the way this year and ended up with a similar solution to Renault.

Now it's only down to Haas and Force India to add S-duct on their 2017 contenders...


Shark fins and T-wings to be banned on safety grounds?

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Following the launch of the first few cars in launch week, voices were raised that shark fins, engine cover sails, or whatever they would need to be called, should be banned from Formula One. F1 teams themselves didn't agree however, as Red Bull's attempts to get them banned last summer failed, most likely because some teams were already happily exploring the aerodynamic possibilities of such engine cover extensions.

Now, with testing underway, and literally every car underway with one shark fin or another, and in some cases with additional T-wings attached to them, some in the paddock expect that the fins may well get banned ahead of the start of the season. Such short notice regulation change is possible, but only on the grounds of safety.

Footage shot during today's testing at Barcelona, in this case without a T-wing on the VJM10, shows that there may indeed be a risk of wings breaking off. It would of course be possible to make them more rigid, but such footage could be used by Charlie Whiting to get rid of the appendages.


F1 2017 explained: Power unit changes

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Following up on their videos on regulation changes, Mercedes have now highlighted the impact of these changes on the power unit.

In essence, it comes down to coping with the difficulty of having more full throttle each and every lap, while having to work against the increased drag that comes with the additional downforce. The increased stresses that will be put on the engine have resulted in a slightly heaver power unit for Mercedes, whereas the cooling requirement have also gone up so that the engine does not overheat while it is burning more fuel, and hence rejects more heat.

Mercedes' engine chief Andy Cowell also explains why a 10% increase in full throttle per lap resulting in only a 5% increase in allowed fuel for the race, resulting in the availability of 105kg of fuel for each and every race in the 2017 season. Cowell said "this will at least prevent the crazy fuel saving measures that we have seen during 2014".


F1 2017 explained: Key changes

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The regulation changes for 2017 are quite extensive, to such a measure that many designers have said it's their biggest change they have had to cope with in their careers. Lots of details have changed, but there are a number of highly impacting changes, aimed primarily at increasing downforce and enhance the way a Formula One car looks.

The front wing for instance will feature a swept forward shape while also being wider by 7.5cm each side. The latter provides additional downforce, while the former is meant to improve the looks as well as lengthen the nose a little bit, enabling teams to pass the front impact tests more easily.

The rear wing was also transformed, located 150mm further back, and 150mm lower while being wider as well, resulting in more downforce and an increased cooperation with the diffuser, which will additionally provide more downforce. Even though it could complicate designs a little bit, there was always going to be the necessity of a rear wing redesign due to the larger diffuser.

Thanks to Mercedes, we've got the highlights lined up in two clips. One indicating car changes, the other highlighting the impact of the wider tyres we'll see in 2017.


Blown wheel hubs continue to be tricky business

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Blown wheel hubs have been adopted by a large number of teams this season, but the feature continues to keep aerodynamicists busy.

At Monza for instance, Red Bull Racing briefly tested an alternative to the open wheel hubs by putting a conical cap inside each front wheel's axle. The cap did appear to have small apertures to still allow some airflow to get through, but clearly much less than what would otherwise be possible. Both cars however were running the usual open hubs in qualifying and the race.

The test is particularly interesting as it comes just one week after the Belgian Grand Prix, where Ferrari also did some running with the front axles covered up.

Difficult to get right

Open wheel hubs already date to 2013, as they were first seen on the Williams FW35 with Red Bull using a similar system that same year. Modifications to pitstop regulations, requiring a safety pin to be fitted to prevent wheels coming off, saw the system disappear in 2014 before redesigns reappeared on various cars at the start of 2015.

It works by sending part of the airflow caught by the front brake ducts through the axle, where it exits through the aperture to manage airflow in the wake of the front wheels. As this obviously requires larger - and more draggy - brake ducts, the system is, as always, a tradeoff between more airflow alongside the inside or the outside of the front wheels.

The system is generally speaking fairly difficult to get right, not least because its downstream effect is influenced by the rotation of the front wheels, yaw and pitch. This makes it complext to simulate reliably in the wind tunnel.

While many teams are using it, the fact that Mercedes isn't shows it's not a straightforward solution. Paddy Lowe confirmed during winter testing his team is looking at it from time to time, but have found that other development routes are more beneficial.

It's interesting how Red Bull's and Ferrari's tests came at circuits that require relatively little downforce. This suggests that the design is less of an advantage on high speed circuits, and instead helps downforce with some drag penalty.

It will be interesting to see how this evolves, and if Mercedes will ever decide to implement this design on their dominant cars. It may be that next year's wider tyres will make this system less, or even more interesting as well.