Development of Novel Non-Pneumatic Tyres to Improve Comfort and Energy Efficiency of Manual Wheelchairs

This project explores Flexible-Spoke Non-Pneumatic Tyres (FS-NPTs) as a new technology to replace conventional wheelchair tyres and improve the quality of life of wheelchair users. From an engineering perspective, a suboptimal wheelchair tyre means uncomfortable rides, reduced mobility, and increased risk for injury. However, what wheelchair users consider to be an optimal (or suboptimal) tyre has remained relatively unexplored. Wheelchair users experience discomfort due to poor suspension (related to tyre vertical stiffness) and fatigue/injury (related to shear stiffness) due to the drawbacks of current wheelchair tyre technology. These drawbacks include inferior suspension, regular pressure maintenance for optimal performance, and puncture possibility (which severely hinders operation), highlighting the need for new technology. To assess the advantages that FS-NPTs could potentially offer wheelchair users, a method of predicting their mechanical behaviour was required. A systematic literature review on FS-NPT technology was conducted and utilised to inform finite element methods to efficiently design and predict the mechanical response of an FS-NPT with optimal structure (honeycomb structure) based on the design of its internal spokes. To determine the feasibility of this technology, the behaviour of current wheelchair tyre technology required quantification, and so wheelchair pneumatic tyre laboratory tests were conducted to acquire baseline tyre characteristics. To efficiently design an FS-NPT with wheelchair tyre characteristics, a tuning protocol was developed combining Taguchi methods with statistical modelling to design a tyre (through spoke geometry manipulation) that possessed the same vertical stiffness as the wheelchair pneumatic tyre. To fully assess the advantages of this technology, a mixed methods approach was adopted. A questionnaire was developed, and the feedback of 117 wheelchair users was received. The questionnaire findings illustrated that the needs of manual wheelchair users are being compromised by current tyre technology. This research was used to inform the design of the FS-NPT concept. Integrating social science research with mechanical engineering and biomechanics, the needs of wheelchair users were translated into mechanical constraints/objectives, and the tyre was tuned to possess ii improved values of shear stiffness and mass compared to conventional tyre technology. The final concept produced was a tyre that can provide similar comfort of a pneumatic tyre whilst being easier to propel, and can also provide additional benefits including tyre longevity, low user maintenance, and puncture-resistance. The findings of this project provide a strong foundation to develop and implement this technology in the future to improve the quality of life of wheelchair users.