| Popis: |
Mountain bike suspension systems have been designed to improve riding performance and comfort for the cyclist. Additionally, a suspension system may reduce fatigue, energy expenditure, and enhance time trial performance. It has also been proposed, however, that using a rear suspension system on a mountain bike may be detrimental to the cyclist, causing the cyclist’s energy to be dissipated via the rear suspension system. Prior to undertaking the current research, a survey into mountain bike suspension systems was conducted to establish rider preferences, as well as their perceptions of suspension systems and riding styles. The resulting responses - that the majority of cross-country cyclists chose to ride a bike with front suspension only (a hardtail bike), despite the significant advantages that a fully suspended system has to offer – aided in the decision to address the unanswered questions that remain in this area of research. This thesis presents an investigation into mountain bike suspension systems and their effect on rider performance, quantifying the dynamic loads exerted on the bike frame and rider. Both the psychological and physiological effects of using a rear suspension system on cross-country cycling are additional considerations of this study. An initial laboratory experiment was completed to investigate the effects of rear wheel dynamics on a rough track with a high impact frequency and the consequent impact this terrain has on rider performance, comparing a full suspension and hardtail bike. Further testing was conducted on a rolling road rig, specifically designed for the purpose of the current research, which more closely represented the conditions encountered by a cyclist on a cross-country track. Testing was conducted on the rolling road rig on both a flat road and rough track, examining the interaction forces between the bike and rider. Greater resistance was experienced by cyclists when cycling on the rolling road rig compared to the roller rig which equated to the resistance encountered when cycling uphill or into a headwind. The mechanical results from both rigs were compared to dynamic simulations as a means of validating and comparing the mechanical results. An additional series of tests was carried out on an indoor track which had a similar terrain to that of the rolling road rig. This set of tests placed fewer restrictions on the cyclist as only physiological data was collected using unobtrusive portable measurement devices, and provided further results to illuminate correlations or discrepancies between the roller rig and rolling road rig experiments. The experimental rolling road rig results indicated that, when cycling on a smooth surface, the hardtail bike offered no significant physiological advantage to the cyclist; however, more power was required by the rider to pedal the fully suspended bike. This was also advocated by the simulation results. Conversely, it was highlighted that the fully suspended bike provided a significant advantage to the rider compared to the hardtail bike when cycling on extremely rough terrain on the roller rig. This was the case across the simulation results, mechanical measurements, physiological measurements and psychological measurements. Similarly, the indoor track tests indicated that cycling on a fully suspended bike provided significant advantages to a cyclist in terms of rider performance. On the contrary, the experimental rolling road rig results on a rough surface demonstrated that no significant difference was apparent between cycling on either the hardtail or fully suspended bike. This result suggests that, when a rider encounters added resistance to cycling, as is the case when cycling uphill, there is less of an advantage for a fully suspended bike even on rough terrain. |
