| Abstract [eng] |
In this study, a new hybrid compliant in-wheel micro-suspension, inspired by the Chinese finger trap (CFT), was developed and tested. The research problem was identified as the limited radial compliance of the conventional tensioned bicycle spokes, as well as the instability that was experienced when a full-length CFT structure was used as a spoke-like element in the past. The validated nonlinear compliance of the CFT mechanism was reformulated in a hybrid coaxial architecture, applying a staged engineering design methodology. In this architecture, compliant regions, which were derived from CFT, were integrated locally with coaxial tube sections for support, alignment, installed stiffness, and buckling resistance. The design was evaluated for an 80 kg bicyclerider system, a 675 N screened service load, a maximum service hub deflection of 2.50 mm and a minimum impact hub deflection target of 10 mm. The 29,400 profiles were screened with a parametric MATLAB process to evaluate their geometric admissibility, installed-state support, branch-force participation, service-state feasibility, spoke-count requirement, buckling safety and impact-response. There were just four profiles that met the full thesis criteria, which indicates that the feasible design region was very small. The profiles 7376 and 13224 were then realized in CAD and evaluated using the SolidWorks component simulations. Profile 7376 was determined to be the compliance oriented candidate with 14.54 mm predicted impact hub deflection and 20.87 mm lock margin. The support oriented candidate, profile 13224, was determined to have 0.95 mm deflection at the service hub, 10.00 mm deflection at the impact hub, and was deemed to be a viable 20-spoke configuration. Experimental observations verified the nonlinear stiffening behaviour of the CFT mechanism, and the importance of branch-load balance to the durability of the hybrids was also found. The hybrid CFT spoke was determined not to be a commercial ready component, but a validated design pathway was set in place to move a compliant mechanism to a wheel relevant spoke architecture. |
