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Wheel aerodynamics

At first glance, wheels may appear to be a fairly simple component, but in Formula One they are in fact highly optimised aerodynamic devices. The airflow through a wheel can have a considerable impact on the overall aerodynamic performance of a car, and is the subject of intense development by teams. Although the FIA has tried to regulate out such developments, teams are constantly finding ways to circumvent the rules to gain improved performance. So what systems have been devised to eke performance from these seemingly humble components?

The wheel cannot be viewed in isolation, and the various designs developed by teams to condition the airflow through the wheel are dependent on other parts, such as the brake cooling ducts, to be effective. The flow coming off a car’s bodywork, notably from the front wing, also plays a key role.

Over the years, various teams have gone to great lengths to optimise this area of a car’s aerodynamics; the biggest developments took place over the 2006 and 2007 seasons. Instead of simply sculpting the wheel, teams – notably Ferrari – began to use disc-shaped devices that covered the outside of the wheel but that did not rotate.

Making these devices work effectively was no easy task, however, as Pascal Vasselon, of the then Toyota F1 team explained in 2007. “The effect of the front wheel blanking is not something you can capture very simply,” he said. “We now have some experience with it, and clearly it can have a totally different effect according to the rest of the flow structure over the rest of the car. It’s a powerful item, and you can use it in different ways. It’s not only a drag reduction item; it really can change a lot of things in terms of front-wheel wake – you are of course playing with the font wheel wake. It requires careful tuning according to the rest of the car.”

Over the next four years these devices developed into some extreme designs, which in some cases even ended up being extended around the rear of the tyre. Despite the sweeping regulation changes introduced in 2009 to ‘clean up’ the aerodynamics of the cars – intended to reduce the impact of a car’s wake on the cars behind – wheel covers managed to survive. Come 2010, however, the FIA decided they had to go, and revised the regulations to eliminate them.

Ferrari managed to circumvent the new regulations by incorporating an aerodynamic device into the wheel structure itself. This was a cunning move, as rims must be homologated for the whole season, and thus none of its rivals was able to copy the design. Suffice to say, the FIA felt these went against the spirit of the regulations, and for 2011 introduced regulations strictly governing the form of the wheels. This hasn’t stopped teams pushing their development though, and many have devised new means to improve the flow conditions around the wheels.

2012 saw Williams develop a ‘scoopless’ brake duct for the FW34, in an effort to help control the airflow in the area between the wheel and the chassis, while still helping to condition the flow around the outside of the wheel. The design achieves this by using a hollow axle that terminates before the wheel nut and is thus within the regulations. The air is channelled from the brake duct through the axle and out over the wheel rim, the duct being fed by a small gap between the top of the duct and the inside of the wheel.

2013 has seen several other teams adopt similar solutions, as well as further developments to channel air out through the front axle. Red Bull tried a similar solution with the RB8 in 2012, but the design vented air outboard of the wheel nut and was thus deemed illegal.

The fact that teams will dedicate so much ingenuity and effort to such relatively small aspects of a car’s design highlights the level of design optimisation the current generation of cars achieves.

Written by Lawrence Butcher

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