Dua(e)l Axis Steering

        During every race weekend, Formula One fans will be shouting and screaming like anything to the real-life drama happening on the track and in the pit lanes. But F1 2020 season exceedingly rued the fans, as most of the Grand Prix canceled due to COVID-19 pandemic and the confirmation of Sebastian Vettel leaving Ferrari after 2020. After the protracted winter break, F1 2020 season kicked off with a substantial drama at the end of free practice 2 of the Austrian Grand Prix. Red Bull had lodged an official protest against Mercedes’ DAS system, as it is alleged to breach two specific technical regulations. One is “no adjustment may be made to any suspension system while the car is in motion” and another regarding aerodynamic influence. 

        Besides being a huge Tifosi of Scuderia Ferrari, I’m here to explain Mercedes’ innovation, the Dual Axis Steering System. Since it is a pure engineering marvel. Mercedes Petronas AMG F1 team made all the headlines long ago on Day 2 of Winter Testing when they revealed that they had developed a Dual Axis Steering (or DAS) system which changed not just the steering angle of the wheels but the toe angle between them. To help understand why this system is so beneficial we need to go over what toe is.

        Toe is technically part of the suspension setup that will be adjusted for each particular track. It describes the angle of the wheels relative to the perfect straight forward direction of the car. So wheels with zero toe will point straight ahead. Wheels with positive toe will point inwards, towards the centreline of the car. Wheels with negative toe will splay outwards. So what are the effects of the toe? Common sense would have you think just get the wheels pointing parallel with zero toe and then get them moving left and right together as you steer the wheel. Why on earth would you point them off-center? Well, there are quite a few things that are affected by the toe angle. The first thing affected by the toe angle is tire wear. This should become quite apparent if you think about it. With zero toes, the front wheels are pointed straight ahead so as you drive the car forward the front tires are just rolling freely on their axes. If the tires are splayed out, the inside will be dragging somewhat along the track, heating and wearing the inside of the tread. Similarly, if the tires are toe-in, the outside of the tire tread will be dragging somewhat along the track causing temperature and wear issues that will need to be managed. With only a degree of toe, these problems aren’t as catastrophic but they still need to be taken into account. To minimize wear, you’d probably want to keep to zero toe, particularly on the straights. Again, all things being equal, zero toe will give you the best straight-line speed. If you introduce toe angle to your front wheels, they are wanting to go in a slightly different direction than straight ahead so you’re essentially wasting power dragging them along the track instead of free-rolling as previously. It may only end up being a matter of a few km/h but anyone familiar with Formula 1 knows that the little things soon add up.

        Now we move into an area where zero toe might not be your best friend. Let’s think about what happens when you turn a corner. Let’s imagine you driving your F1 car into and around a right-hand turn. Your front wheels should trace out curves and What’s important to realize is the inside tire is always tracing a tighter curve than the outside tire. You know as the turning radius gets tighter and tighter, so you have to steer more so ideally you’d want the inside tire to be more angled through the corner than the outside tire. This allows both tires to more closely follow their turning curves, maximizing their grip and increase your speed and stability through the corner. You can achieve this by adding angling your front wheel toe outwards. On Straight, yes, the tires look weird and splayed. But once you turn the steering to drive through a corner, the inside wheel is now more aggressively angled to take the tighter line, while the outside tire is more gently angled to take the wider outside path. Toeing your wheels inward makes the car less planted through turns as the car is more reluctant to turn as the closer you get one tire to the correct steering angle, the more you point the other away, causing drag and resistance at the front end of the car. This leads us neatly to the last major effect of the toe which is straight-line stability. Let’s put our cars back on a long straight, but think about what we just said about cornering. Toe out makes the car absolutely ready to turn. As soon as you start to turn the steering, the wheels are toed so that they encourage the car to turn in, with the inside wheel angled aggressively to take the tighter line. This means that while the car will keep pointing straight as long as you hold the steering straight, the moment you make a slight adjustment away from the center, the car is more sensitive to turning. And holding the steering perfectly centered can be difficult when the car is bumping around or one tire hits a crack in the road. Little disturbances can make the car want to hoik itself left and right. Conversely, when the front wheels are toed in, they are reluctant to turn. They respond much more lazily to steering inputs which means the car will remain stable on the straights, even if bumps and such some disturbances in the steering. Now, normally teams lock in a toe setting that’s the best trade-off between tire wear, straight-line speed, cornering speed, and straight-line stability as determined by the track and other parts of the suspension design and setup. Most setups are a matter of trade-off after all where gains in one area result in losses in others. But what Mercedes have now managed to do, without apparently breaking the rules, is give the drivers the power to adjust the toe angle while driving by pulling back and pushing forward on the steering wheel. The Dual-Axis Steering system allows the driver to pull back on the steering wheel to bring the toe-in, and push forward on the wheel to pull the toe out. This has several ramifications. The obvious one being that they can straighten up the tires for the straights, to increase their speed, reduce wear and rising temperatures on the inside tire tread and give the car more stability, while also pulling the toe out for the corners for increased handling and speed.

        A simplified version of all the above is zero toe good for straights, negative toe good for corners. Mercedes can handle that. But of course, the toe isn’t just a matter of in and out. There are fine adjustments in between. All corners are different. If the Mercedes drivers get a good feel for the DAS they can try and get the toe as close to perfect for every different type of corner. A tighter corner would benefit from a more dramatic toe out as the relative difference between the inner and outer lines is more pronounced. On another note, I’ve sort of spoken about rising tire temperatures as if they’re a bad thing, but getting heat into the rubber is an important part of the performance. And getting the right amount of heat across the whole tire is particularly important. As mentioned, when tires are toed out they tend to overheat the inside rubber and vice versa with when toe-in. But the Mercedes drivers could potentially fiddle with this on straights to balance the temperatures across the tires. This is particularly useful on out laps to prepare the tires for a hot lap, but even if they’re told mid-race that the outside rubber is getting a little cold, they can toe in to try and help that part of the tire get into the sweet spot. This is a great, clever, innovative system. It’s not the be-all and end-all of a competitive car but it will help Mercedes particularly across race distances when managing the performance of their tires.

        Though Mercedes previously insisted that their new system is legal, now Red Bull is seeking the closing time clarification to FIA. So that Red Bull can gear up the RB16 with their own version of DAS if FIA rule it is legal, which Christian Horner hinted earlier. Tomorrow prior to free practice 3 of the Austrian Grand Prix, FIA race stewards will make the final decision on this protest. This is a one-year-only thing as the rules for 2021 appears to not allow for such systems. But the new F1 regulations are to be delayed until 2020 due to the pandemic. So enjoy it while it lasts and sees if any of the other teams can squeeze their own version during the season somehow.