The Mercedes-AMG Project ONE's Complex Suspension Explained
The new generation of hypercars is coming. While the Aston Martin Valkyrie seems firmly set on leading the charge from an aero front, the Project ONE has instead focused on the more classic approach of improving the mechanical side of performance. Fitting a powertrain straight out of an F1 car (plus added motors of course!) comes with obvious performance benefits, however what is less intuitive is the function of its rather interesting suspension setup.
When thinking about modern car suspension we often think of it in terms of springs and dampers on each wheel of a car. We use these to control the motion of each wheel over bumps and in manoeuvres involving body roll, acceleration squat and dive under brakes. However, when dealing with the handling performance of the car, particularly on track, it turns out that this is not the best way to do this.
Suspension changes can actually be classified into a number of different "modes" that we can tune around, depending on what is happening to the car. For example, one mode is roll, where the wheels on one side of the car are forced up and on the other they move down. Another is four wheel heave, where all four wheels move up with respect to the chassis, such as what happens when downforce compresses the car into the road. For any car with very high aero loadings, the requirement for high heave stiffness is immediately apparent, as if the heave stiffness is low, the car will quickly bottom out to the bump rubbers. This is not ideal (unless you are in a regime where you want to run on bump rubbers, but this is a whole other subject). There are other modes, such as pitch and warp, but we'll just talk about heave and roll for now.
With conventional spring/damper setups, the only way to increase heave stiffness is to increase spring stiffness, however this also increases effective roll stiffness. This means that if we want high resistance to bottoming out under aero loads, we must compromise our roll stiffness. On top of this, if we wished to tune roll stiffness independently of spring stiffness we would need to fit an anti-roll bar, which is undamped. Thus it can be seen that we would ideally like our own spring and damper for each mode, and this is exactly what the Mercedes system does.
As explained diagrammatically in the video, the top spring/damper combo is the heave spring, and the lower, angled spring/damper is for roll. These then are actuated by the suspension bell cranks to ensure they only act on one of the modes. The roll damper needs two sets of springs as the car can roll in either way, while the heave damper only has to have a single spring as the weight of the car is always pressing down on it. Through this system Mercedes has cleverly isolated the modes and allowed the Project ONE to maintain good mechanical grip whilst still being able to deal with high aero loads.
Kyle Forster is a qualified Aerodynamicist, race car engineer, and the man behind JKF Aero, a firm that offers a variety of aerodynamic consultancy services for racing purposes. If you have any questions for Kyle or have any suggestions for future videos, drop them in the comments below!