مواد و روش ها برای ارزیابی رفتار سازه شعاعی از چرخ های دوچرخه مسابقه

Aim of the work was the development of a test method for evaluating the radial structural behaviour of racing wheels, believed to be correlated with the riding comfort properties. Four front wheels of different shape, material and spoke disposition were equipped with the same tubular tires and tested under radial loads. The wheel/rim/tire load-displacement curves were measured in static, cyclic and bump tests. The stiffness varied with load: despite great differences in the rim behaviour, the wheel overall behaviour resulted very similar due to the tire masking effect.

The perceived quality of a racing wheel is related to the combination of several performance parameters with the level of comfort during long cycling tracks on irregular road textures. Cruising comfort is related to the radial behaviour of the wheel assembly, intended as combination of tire and rim. Radial properties of wheels are believed to be dependent on tire pressure and construction, rim profile and materials, spoke design and disposition, hub shape and materials. Despite the common opinion among cyclists that the wheel radial properties affect the rider’s back comfort, previous studies were focusing mainly on the effects of rider’s weight (Stone & Hull [1]) or on the frame materials (Hastings et al. [2]). Very few studies were analyzing the structural radial behaviour of wheels and their correlation with the degree of rider’s comfort. The aim of the present work was the development of a standard test method for the quantitative analysis of racing wheels in terms of static and dynamic radial behaviour.

A new methodology for evaluating the radial structural properties of racing bicycle wheels was proposed: the constant behaviour of the tire obtained from different wheels during the dynamic bump tests was assumed as a validation of the test method. The work showed that high differences in rim stiffness were not corresponding to great variations of the wheel assembly radial stiffness at a typical cycling pressure of 8 bar. The tire stiffness was able to mask the rim differences, thus involving further detailed analysis of the perceived wheel comfort behaviour on the road and its correlation with the wheel structural parameters.