Development of a test bench for the subjective & objective evaluation of the vibrational comfort of bicycle components

Vibrational comfort is one of the most important parameters evaluated by cyclists and it is correlated to the response of bicycle components in combination with the cyclist's characteristics. Vibration transmissibility of wheels and saddles had been recently studied during lab tests using a wooden dummy bottom resting on the saddle and in road tests on an instrumented racing bicycle at different speeds on different surfaces. In this study, a test bench was developed in order to simulate different vibrational inputs to the seatpost from the road surface on a group of real cyclists during steady cycling. The bench is composed by a racing bicycle without wheels, hinged at the front fork axle and sustained by an hydraulic actuator connected to the seatpost. The bicycle is equipped with pedals and chain wheel and a long chain drives another rear wheel fixed to the bench and connected to brake rollers. Three racing bicycle saddles were evaluated by a group of five cyclists after the application of vibrational spectra corresponding to PSDs recorded in the field tests: the magnitude of the transfer function H between the input vertical acceleration at the seatpost and the output acceleration at the pelvis was obtained by two accelerometers. The cyclists were in the meantime asked to fill a questionnaire regarding the perceived comfort of the three saddles during the tests. Initial results showed an encouraging correlation of the subjective ranking of saddles with the corresponding Index of Transmissibility derived from the transfer function H.