Abstract
Abstract. The basic Whipple-Carvallo bicycle model for the study of stability takes into account only geometric and mass properties. Analytical bicycle models of increasing complexity are now available, they consider frame compliance, tire properties, and rider posture. From the point of view of the designer, it is important to know if geometric and mass properties affect the stability of an actual bicycle as they affect the stability of a simple bicycle model. This paper addresses this problem in a numeric way by evaluating stability indices from the real parts of the eigenvalues of the bicycle's modes (i.e., weave, capsize, wobble) in a range of forward speeds typical of city bicycles. The sensitivity indices and correlation coefficients between the main geometric and mass properties of the bicycle and the stability indices are calculated by means of bicycle models of increasing complexity. Results show that the simpler models correctly predict the effect of most of geometric and mass properties on the stability of the single modes of the bicycle. Nevertheless, when the global stability indices of the bicycle are considered, often the simpler models fail their prediction. This phenomenon takes place because with the basic model some design parameters have opposite effects on the stability of weave and capsize, but, when tire sliding is included, the capsize mode is always stable and low speed stability is chiefly determined by weave stability.
Highlights
The stability of bicycles has drawn the attention of scientists since the development of the first modern bicycles
When the basic Whipple–Carvallo bicycle model (WCBM) is extended by introducing front assembly compliance, the most important effect is the appearance of a high frequency wobble mode, which may become www.mech-sci.net/10/229/2019/
The analysis of the global stability indices (Ssr and SsA) shows that some parameters have an effect on the global stability of the three modes opposite to the one they showed in the WCBM, considering only weave and capsize modes
Summary
The stability of bicycles has drawn the attention of scientists since the development of the first modern bicycles. This compliance commonly includes the effects of the frame head tube, the fork, and the wheel (Doria and Roa, 2017; Doria et al, 2017; Klinger et al, 2014; Limebeer and Sharp, 2006; Plöchl et al, 2012; Sharp, 2008) These models add an additional velocity degree of freedom to the WCBM in order to take into account the lateral velocity of the front-assembly due to compliance. When tire lateral slip is considered at least four degrees of freedom (DOFs) are needed to model the bicycle
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