ENGINEERING
Fitting ducts to cool the brakes on F1 cars seems simple in theory, but in reality this is a red-hot aerodynamic and regulatory battleground
Why brake ducts are more than they seem, illustrated by Piola
Brake ducts? They’re just holes, aren’t they?
When it comes to talking technical in F1, the powertrain and aerodynamics always take centre stage. It’s only natural that attention will be drawn to the audio-visual elements – noise and aesthetic appeal have long been the sensory stimuli that can turn any motorsport fan’s knees to jelly.
But this season has offered new areas of intrigue, with a more radical approach to suspension design, and included within that is a completely renewed focus on brake ducts, which have undergone considerable change over the offseason. In a move designed to stamp out the increasing number of flicks and protrusions from the front brake duct area, the FIA restricted the geometry to fit purely within the radius of the wheel rim. That included the duct itself, meaning that brake cooling required something of a rethink.
At the rear, things are a little different because there are far fewer restrictions. The space available for bodywork means that, from the rear, an array of stacked winglets resemble small DVD racks. In the age of streaming, DVDS lurch closer to the pits of obsolescence, but the continued development of the brake duct-mounted winglets shows little sign of abating.
For 2020, F1’s brake ducts are slated to become a listed part – that is, the bodywork associated with the braking assembly and suspension upright must be produced by each team in-house. Teams are currently able to buy them in from competitors, something that Haas takes advantage of by purchasing the Ferraridesigned ducts and drums.
Cooling for brakes and the usual dissipation of the ensuing hot air has changed with the thinner-gauge Pirelli tyres, which have theoretically become easier to heat up – but also easier to cool down. The fluctuation in tyre temperatures throughout a race have been a lot for the teams to get their respective heads around, and only Mercedes has truly got to grips with it.
A lot of that is down to the suspension kinematics, which seem naturally equipped to get the tyres within the right working range, coupled with the overall downforce generating the right amount of load in the tyres. But in its brake duct design, Mercedes also has another trick - not only does it have the traditional opening to provide the much-needed brake cooling, but it’s also got a small channel built into the “cake tin” - the carbon fibre shroud around the brake assembly.
This is fed by an opening that’s set back from the wheel rim once attached and, as airflow meanders through it is pulled out through the centre of the wheel. This is an attempt to recapture the effect of the blown axle, something that appeared on many cars in 2018 and was banned for 2019.
Ferrari has a different approach, and has been running asymmetrical ducts this season. For a circuit with predominantly right-handed corners, Ferrari has put a second aperture on the right-hand upright, aiming to kick out a bit more heat from the brakes. For anti-clockwise circuits, such as Baku, those designs are reversed. At the inside wheel, its deceleration is greater than that of the outside, aided by the Ackermann steering geometry (the offset between the rotation of the left and right front wheels to aid cornering), and so there’s a lot more heat to expel.
Those ducts channel airflow out aggressively, through a small opening into an area for expansion – akin to a diffuser – to accelerate it outwards. It’s the design Haas uses, but next year it’s expected the American team will have to develop its own. That’s perhaps not such a bad thing, given the complications it has struggled with in 2019. By developing a bespoke product it could divert some of the excess heat into the tyre, should it suffer a recurrence of its current tyre conundrum in 2020.
In the banning of the majority of aero tricks used to eke the most out of the duct geometry, some teams have come across a loophole. At the front, any non-suspension components can only protrude from the inside face of the upright by 5mm. But by sinking in that inside face, there’s more area to play with.
This opens a space for a number of small fins, which are sharply angled downwards. Able to pick up the rotational flow from the wheel, the fins can turn it away and towards the bargeboard geometry. In that, F1 teams have the outward jet of airflow and the conditioning of rotational flow at both sides to minimise the disruption produced behind.
With ‘listed’ status there’ll be more variations, and when F1 gravitates to 18” wheels in 2021, it’ll be all-change again.
The Mercedes approach
Opting for a brake duct that protrudes inboard more than the Ferrari design, the Mercedes concept links up with its suspension arrangement, which mounts the upper wishbone on a raised ‘horn’. The linkage bracket fits in behind the duct, while the upright face is pressed in.
The Ferrari approach
Ferrari uses the brake casing to channel airflow outwards, aiming to replicate the blown axle effect (inset) that was banned over the offseason. Ferrari has tried to use the hot air from the brake to control the rotational flow from the wheel centre.