Design and Development of Contractive Suspension in Hill-Climb Races

Abstract

The study of racing car suspension is always a key issue when looking for improvements in car performance [1–4]. The experience, knowledge and data obtained in operational conditions is analysed through simulation, allowing adjustments in the car set-up. An advanced design solution is the implementation of a double opposing spring system, commonly used in Formula 1, in LMP1 or LMP2 but not in minor racing [5], named “contractive suspension”. Such designs integrate an additional spring in the damper system to push the tire down into the ground and increase the understeer effect, thus correcting the setup of the antiroll bar. A study was carried out on a Hill-Climb Race Car, starting from the full vehicle multi-body model of the car with the complete front and rear suspensions. The vehicle was simulated running on an uphill track with the primary manoeuvre bring low-speed cornering with high lateral and longitudinal accelerations. To find the best stiffness ratio between front and rear, a contractive mathematical model has been implemented. Simultaneously, the mechanical design process started with the objective of designing a compact system with elastic elements that could be easily replaced and inserted in place of the traditional spring-damper solution. The results, primarily performed in multibody simulation environment and then verified by the measurement data acquired from on the track, showed an improvement in terms of load transfer at contact patch wheel area with respect to the traditional set-up solution. The evident reduction of the vibration level of the wheel with corresponding increase of traction is confirmed by the pilot, who had a better feeling of the car in comparison to the existing solution. Finally, improvement of the mechanical system helped set-up operations during the racing and to achieve weight reduction and space optimization for aerodynamic scope. In conclusion, the adoption of the multibody simulation has been the key aspect to design, verify and optimize all possible variant set-ups before the test phase. Although it is always needed a series of tests for the final tuning, simulation has enormously decreased the time and cost requirements for the experimental development activity, allowing identifying a selected number of optimized set-up solutions.

F2012-E04-014