The work described in the thesis consists in the study and the design of a third element for the suspension, both front and rear, of a high-performance formula car. A third element, also called heave spring, is an additional elastic component with respect to the two corner springs, one for each wheel. It is connected to both wheels of the axle in a way that it works only when the wheels move in parallel travel, i.e. in heave condition, while it gives no contribution to car rolling. In addition to the spring, it is also possible to have a third element with a damper.
The thesis begins with an introduction about the third element benefits for the overall car behaviour and its typologies that are most found in race cars. Then, starting from the basis of the current suspension geometry of the car on which the third element has to be implemented, the component layout and its target stiffness is defined. In order to set a target for stiffness, in particular, a realistic analysis over some driving simulator data has been performed.
During the whole design activity two third element versions have been considered: a first with only an elastic component (simply called mechanical element), and a second version with the addition of a damping element. It is found that for the front suspension both version of third element can be mounted independently, while for the rear suspension two slightly different layouts are required, with different attachment points to the chassis. The final design for the mechanical versions is complete, with the assembly and construction drawings of all the components needed, while for the damped versions the final damper drawings are a proposal, that tries to represent a realistic geometry but that has to be confirmed after a discussion with the damper supplier.
Regarding the mechanical element, the front one employs Belleville washers as elastic component, while the rear one employs helicoidal springs. Both front and rear elements can vary their stiffness within a certain range, according to the targets identified during the preliminary design phase.
As outcome of the design work, compared to the existing suspension, the new components required to mount the third element, besides the same element assembly, are, for the front, the two rockers. For the rear instead are the anti-roll bar and the two brackets for attaching the element to the chassis, one for the mechanical element and one for the damper. All the mentioned components have been structurally verified, by mean of finite element analysis, for the most demanding of all possible load case, depending on the suspension setup.