Formula 1 world champion Mercedes finally turned its W09 into a winner in Baku last weekend – but is under no illusions that it needs to understand it car more to better extract performance from the tyres.
A key area of focus to make progress on this front will be with its suspension system which, as Giorgio Piola’s exclusive drawings and video shows, features some unique ideas.
Packaging the front suspension of a Formula 1 car is no easy task. There are just so many components to find space for – and on top of what we can see there are things we can’t, such as the pedals, master cylinders and, importantly, the driver’s feet.
The tight area to work within means there is a place for everything – and the 2018 Mercedes is no exception.
It has the common top-and-bottom carbon wishbone and a carbon pushrod operating inboard rockers (1).
Where the black top part of the pushrod changes to the silver part there are shims (slightly darker silver) to alter the ride height. As the angle of the pushrod is about 45 degrees, adding a 0.5mm shim will raise the ride height by roughly 1mm.
Looking at the car from the front, it has torsion/springs on both sides (3). The left-hand torsion/spring will be splined into the machined-out rocker.
As the two additional rockers (4) are joined together in the middle with a solid link that effectively creates a third connecting rocker to help the other two drive the anti-roll bar, the small-toothed plate on the right-hand side rocker is to locate the torsion/spring to that rocker. Having this small plate will allow adjustment so there is no preload on the system.
The interesting thing is where Mercedes has fitted the front anti-roll bar. It is inside the left-hand torsion spring (3 indicates the left and right). Its lower spline will fit into a spline on the inner diameter of the left-hand torsion/spring and its top spline will be driven by the small-toothed plate.
When the car sits on the ground and the aerodynamic force starts to build up, the left-hand rocker will rotate clockwise. The right-hand rocker will rotate anti-clockwise and with the solid link connecting them in the middle they will rotate at the same ratio, closing the gap between them, effectively acting as a central damper.
When the car reaches a certain speed that central gap will become zero and the car will then sit on the silver mesh-style bump stop. In a straight line, this will then reduce the car’s vertical movement dramatically as this bump stop is very stiff.
However, in a right-hand corner when the car builds up lateral force and the chassis rolls, the left-hand rocker will rotate anti-clockwise and the right-hand rocker will also rotate anticlockwise. This will then twist the anti-roll bar. In this condition, it is the sum of the anti-roll bar stiffness and the torsion/spring that gives the car its roll stiffness.
Just to explain what a torsion/spring is, it is a round bar or tube with a spline at each end, something like 15-25cm long. One end is anchored to the chassis down at the driver’s feet and the other end to the rocker.
When the suspension moves downwards, it twists the bar and this is the stiffness that supports the car. A larger diameter, a thicker wall thickness, or a shorter torsion/spring will increase the vertical stiffness. The anti-roll bar design is very similar but the function is very different.
The torsion bar (2), power-steering assembly (5) and tyre tethers (6) are also shown.