Will Gray

Tech Talk: How Mercedes have raised their game

Will Gray

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Mercedes struggled to perform in the first three years of their F1 return but things are starting to change.

One of the key reasons is their use of an all-hydraulic suspension system that sees the springs, dampers and anti-roll bars of a traditional layout replaced by a closed-loop hydraulic system connecting all four corners of the car together.

The system, which was introduced in 2011, allows them to control the forces at play as the car travels around the track - but it has taken until now for them to unlock its potential.

The performance of an F1 car is heavily influenced by the way the forces of motion act through the suspension system.

Small bumps on the track surface jolt it around, forces from braking and acceleration cause it to pitch nose-up and nose-down, cornering forces cause it to roll left and right and aerodynamic forces cause significant compression as downforce increases with speed.

The suspension system aims to minimise the negative effects of these different forces, so it needs to be soft enough to smooth out the bumps but stiff enough to reduce roll and pitch and resist compression.

This is important for two main reasons.

To achieve the most effective aerodynamics, it is best to keep the car at a level ride height because any change in the angle relative to the airflow can reduce the downforce and, with such complex flows on the current cars, can even completely alter a desired flow regime.

To achieve good mechanical grip in cornering, it is all about how the car roll transfers the loads due to centrifugal (cornering) force to the outside wheels - and there are certain optimal limits.

The more load that is transferred to the outside tyre, the bigger the contact patch will become as it is squashed by the force and the more grip the car will have - but that comes at a cost because all the work that tyre is having to do wears out the tyre compound. Meanwhile, on the inside wheel, the weight transfer can reduce the load to the point where it can also create tyre wear through scrubbing on the surface.

So in low-speed corners, where grip from downforce is low, mechanical grip is a priority and the more load fed to the outer tyre the better. In the high-speed corners, where more grip is provided by downforce, less mechanical grip is needed and reducing load transfer to the outer wheel will reduce tyre wear.

A traditional suspension system has independent front and rear parts, with the forces between each side managed to a certain extent by roll bars.

Renault (now Lotus) introduced a hydraulic connection between the front and rear suspension several years ago – giving them the ability to manage pitch motion - and most teams now use that system.

But Mercedes’ FRIC (Front and Rear Inter-Connected) system – which actually has its heritage in 1950s road cars - takes that one step further.

By connecting all four corners of the car together using tubes of hydraulic fluid, valves and actuators in a closed loop, the system can control roll and pitch in combination and can be finely tuned to passively change how this is done through a lap.

At each wheel, the pull/pushrod rocker connects to a hydraulic element in place of the traditional damper, and the load at each wheel creates a pressure on the fluid in that element.

That pressure feeds through the tubing to tuneable valves which are set up to either block or allow the force to pass and direct it to different areas of the suspension, depending on pressure differentials.

That enables the system to distribute the force around the car to stiffen or soften the suspension at each wheel, depending on what it needs – taking load off one wheel and adding it to another.

Under braking, when the car goes into pitch, the pressure on the front wheels is transferred to the back wheels through the fluid and that reduces the downward push at the front and stops the car nose diving (or vice versa for acceleration).

In roll, the system can be tuned to feed more or less load into the outer wheel. So, in slow corners, it can put the outer wheel under greater load for increased mechanical grip and in faster corners it can even out the weight distribution to reduce the wear on the outer tyres.

Unlike the other systems, it can do this in combination and use one to help control the other. And crucially, given the tendency for this year’s tyres to be extremely sensitive to front/rear balance, this inter-connected distribution of load could give Mercedes a significant advantage in tyre management.

It also gives Mercedes more control over the ride height of the car throughout a lap, allowing them to manage and more accurately predict changes due to varying speed and downforce – something that has likely helped with the aerodynamic improvements they have made this season.

Mercedes have put in plenty of time trying to get this system right and understanding precisely how to tune it has been key to finally reaping the benefits.

Lotus is already believed to be close to finding a solution and surely the rest will follow. But as Mercedes has shown, having a system is one thing, making it work is another – and they will be hoping it takes their rivals a while to work out the secrets while they reap the benefits...

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