Abstract

Owing to the high magnitudes of vibration transmitted to the snowmobile driver, ride comfort forms a major design requirement. Current development processes are based upon prototyping and sequential field-testing. An analytical model for investigating the dynamic snowmobile behaviour would enhance the designers' efficiency at achieving the desired ride performance. In this respect, only limited efforts have been made thus far. This dissertation research aims at developing a comprehensive, industry-viable ride dynamic model of the snowmobile to help in vehicle development. A nine degrees-of-freedom model was implemented in the ADAMS software through the integration of nonlinear subsystem models, namely, a lumped frame model, detailed suspension representations, a track model, deformable ground model, trail surface representations, a quasi-steady traction model, and a simplified rider and seat model. Four different trails were measured and analyzed, characterizing their roughness in terms of spatial power spectral density. A field test program, undertaken with Bombardier Recreational Products Inc., provided the vehicle response data. Laboratory measurements were performed to obtain static and dynamic properties of the vehicle and its components. The measurements were compared to the model outputs to evaluate its validity, revealing reasonably good agreements for some of the trails, while considerable differences were observed for others. The model was then used to perform a parametric analysis on nine ride-related factors. Following the response surface methodology, with seat surface vertical rms acceleration as response variable, lead to the identification of a range of parameter values reducing acceleration by 58%. The process revealed, among else, the model's high sensitivity.