Setup of a 1D Model for Simulating Dynamic Behaviour of Motorcycle Forks 2009-01-0226

Shock absorbers and damper systems are important parts of automobiles and motorcycles because they have effects on safety, ride comfort, and handling. In particular, for vehicle safety, shock absorber system plays a fundamental role in maintaining the contact between tire and road. Generally, to assure the best trade-off between safety and ride comfort, a fine experimental tuning on all shock absorber components is necessary. Inside a common damper system the presence of several conjugated actions made by springs, oil and pressurized air requires a significant experimental support and a great number of prototypes and test. Aimed to reduce the design and tuning phases of a damper system, it is necessary to join these phases together with a numerical modelling phase.

The aim of this paper is to present the development of a mono-dimensional (1D) model for simulating dynamic behaviour of damper system. In particular, a conventional telescopic fork produced by PAIOLI MECCANICA has been considered as testing bench. It is important to underline that the same approach could be used to simulate the dynamic behaviour of an automobile shock absorber system. Fork numerical modelling has to assure a faster design process and a performance optimisation, reducing at the same time the design time between the product idea and its final assembly. PAIOLI MECCANICA had the necessity of modelling its forks in order to quickly test different solutions and to improve actual fork performances. The present research concerns only fore-carriage forks for road applications, i.e. forks used in motorcycle not dedicated to races.

The fork model is developed in AMESim code using both hydraulic and pneumatic libraries. A sinusoidal displacement is directly impressed to the fork rod at different axial velocities (from 100 to 2000 mm/s) for simulating the axial excitation imposed to an actual fork by the road discontinuities. Numerical results are compared with experimental data recorded by PAIOLI MECCANICA. In particular, the fork numerical model demonstrates of being capable to reproduce the testing fields typically used as experimental test bench for motorcycle forks.