Technical F1 Unlocked
TECH TUESDAY: The intriguing design details behind Mercedes’ major W14 upgrade in Monaco
Mercedes were predictably the centre of attention before the Monaco Grand Prix weekend as their heavily updated car was finally revealed. Although we looked at that update – which comprised major sidepod and front suspension changes – last week, here we focus specifically on the detail of the new suspension.
We can see that the forward upper wishbone has been mounted much higher than before. The angle between the forward upper wishbone and the rearwards upper wishbone determines the amount of anti-dive in the geometry. Previously on the Mercedes that angle was around 15-degrees. Moving the forward wishbone higher has increased that to around 30-degrees.
The more the suspension can resist the natural dive of the car under braking, the less the aerodynamic platform of the car is compromised. This is particularly important with the ground effect generation of car, as the downforce created by the underbody is enhanced considerably the lower the floor can be run. In simple terms, with less dive to account for, the floor can be set lower and the underbody downforce increased.
What the resistance to dive also allows is less movement in the centre of aerodynamic pressure between braking and the car levelling out, making it easier to give a consistent balance in the various phases of the corner between braking and exit.
Generically, this generation of car tends to be a little unstable under braking but suffer mid-corner understeer, which is the worst of both worlds and arises from the fact that the throat of the underbody venturis are by regulation quite a long way back in the car, so giving an aerodynamically powerful rear in steady-state cornering but with a lot of forwards migration under braking, giving that sensation of rear instability when the car is diving.
But having a lot of anti-dive in the suspension is not all upside. The way the braking loads feed through the suspension, combined with the reduced dive, gives less sensation to the driver as they try to modulate the pedal pressure to match the downforce acting upon the front wheels.
Mounting the forward wishbone higher will also alter the way the geometry works laterally under cornering. It will give the effect of increasing the height of the car’s front roll centre (the notional point around which the car rolls in cornering, and so the higher it is, the more roll is induced).
The rear suspension also has its own roll centre. An imaginary line joining the roll centres of the front and rear suspensions of an F1 car (called the roll axis) will usually be nose-down (i.e. the rear roll centre will be higher than the front).
The angle of that imaginary line determines whether the car is trying to oversteer or understeer. Increasing the front roll centre will reduce the angle of the front-rear roll axis, which will have the effect of increasing understeer, particularly in slow corners.
So, there are significant trade-offs to be made just in the way the suspension works mechanically. But what Mercedes have also done with this change is make it part of the aerodynamic change. With the new sidepod, Mercedes are trying to induce as much airflow as possible down the channels in the side and to the floor edges.
The sidepod channels are taking the airflow over the top of the rear diffuser. The floor edges are trying to seal the underfloor so there is a greater pressure drop beneath the floor, sucking the car down harder. The inlets to the underfloor tunnels beneath the sidepod are feeding the underbody.
With the new higher front-top wishbone, Mercedes have been able to align that with the push-rod, the rear-top wishbone and the lower rear wishbone to give a cascading aerodynamic downwash towards the tunnel inlets, lower sidepod and floor edge.
This would have been impossible to do with the Red Bull’s pull-rod front suspension layout as the pull-rod is laterally aligned in the opposite way to the other suspension arms. But with the Mercedes push-rod system, the push-rod aligns the same way.
Mercedes have been forced to adapt their changes around the existing tub, which was designed for a very different aerodynamic package. But it’s still been possible to open up new avenues of aero development.