Formula 1 enters the month dedicated to single-seater presentations, an object of great anticipation to appreciate how the individual teams have interpreted the new regulations. Among the novelties of the upcoming technical cycle stands out the complete revolution on the suspension front, including the drastic simplification of the internal components which bans the inertters and the hydraulic or gas springs. Equally stimulating element for designers is the redefinition of the geometry of the frame, which in turn forces us to revisit the architecture of the suspension schemes. One of the central themes in the long weeks of winter break that will come alive further during the presentations is precisely the contrast between the two possible philosophies for the front suspension, namely the push-rod and pull-rod scheme.
The push-rod architecture requires that the connecting element between the wheel assembly and the components on the edge of the body is inclined along an ascending direction going from the wheel towards the frame. This rod is also characterized as a strut, as it is stressed in compression by the raising of the wheel unit relative to the frame, a condition that occurs when passing over a curb or with the inclination of the car body towards the outside during the rolling movements when cornering. On the other hand, the pull-rod scheme provides that the rod is subjected to traction in the same conditions in which it is subject to compression in the push-rod. The inclination of the tie rod is also mirrored, with a downward trend from the wheel unit towards the body. In the recent period, the Formula 1 teams have conformed to a pull-rod scheme at the rear and a push-rod architecture at the front, with rare exceptions which, however, have not enjoyed particular popularity. In such a context, the question arises spontaneously what could be different to it that would push the stables to subvert the existing schemes. In fact, it is widely believed that the new regulations open up the possibility of re-proposing the pull-rod scheme also at the front. McLaren itself has released some clues on its social channels, the latest on the occasion of the MCL36 fire-up, which suggest a tie-rod pattern on the front of the Woking car.
The first element in support of a pull-rod architecture for the front suspension is the 12% lowering of the nose of the cars, with the maximum height of the most advanced section of the body going from 625 mm in 2021 to 550 mm in the 2022. At the same time, the external diameter of the tires increases from 660 to 720 mm, which is why the wheel center is at an increased height of 30 mm compared to the last technical cycle. Finally, the increased diameter of the rim, increased from 13 to 18 inches, results in a larger free volume inside it to place the hub holder to which the suspension arms are attached. Overall, on the wheel side the rod can anchor at a maximum height of approximately 590 mm, well 95 mm more compared to 2021. The enlargement of the wheel unit and the lowering of the frame therefore contribute to reducing the difference in height between the two elements, simplifying the creation of a possible pull-rod scheme with the tie rod directed towards the lower part of the body.
However, the feasibility of the front-end pull-rod alone is not a guarantee of its renewed popularity among designers. First, it also comes into play the effectiveness of the kinematics and of the transmission ratios between the movements of the wheel unit and the actuation of the spring-shock absorber unit on the body. Everything was evaluated by the designers also in view of the different needs in the exploitation of the tires and in the stabilization of the aerodynamic platform, the latter based on a completely different load generation philosophy compared to the recent past. The overall budget also includes the compliance of the two suspension schemes, i.e. how much the deformation of the rod and of the other elements under the action of external loads compromises the normal kinematics of the suspension. The tensile or compressive stresses of the pull rod and push rod strut respectively lead to different deformation mechanisms and amplitudes.
To the kinematic considerations are added the evaluations on the distribution of the masses, in particular on the height of the center of gravity. In a pull-rod scheme, the spring-shock assembly housing low in the frame contributes to lowering the car’s center of mass, benefiting the grip guaranteed by the tires thanks to a marginal reduction in load transfers towards the external wheels when cornering. On the other hand, the push-rod architecture provides for the installation of the internal components of the suspension group in a raised position, thus raising the center of gravity.
Finally, also some aerodynamic evaluations, in particular of the blocking exercised by the suspension arms to the flows directed towards the center of the car and towards the entrance of the Venturi channels. The different aerodynamic influence between the two architectures depends on the different position and inclination of the rod, but also on its section. The predominantly tensile stresses of the tie rod in the pull-rod scheme in fact allow a different sizing and a more slender section compared to the strut of a push-rod, thus freeing up a larger area for the passage of flows.
Without supporting data and simulations, it is difficult to establish in advance which philosophy may be dominant or whether there can be an effective differentiation between the cars. Similarly, there is no certainty as to whether one solution will generally prove to be better than the other. A more effective scheme in the aspects of vehicle dynamics and in the damping of loads, benefits felt to a greater extent in low-mileage curves, could instead prove compromising in the aerodynamic behavior of the car, discounting a deficit in high-speed sections and therefore on particular types. of paths. Furthermore, the goodness of the architecture of the suspension scheme cannot be judged in its own right, but only within the general setting of the car. Contrary to the aerodynamic look, however, a possible wrong choice for the suspension group will not be easily changed during the current season, which is why the suspensions become one of the main elements of interest of the new single-seaters. All that remains is to wait directly for the cars to be presented and then for the track to be confirmed.
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