Design and Preliminary Engineering Evaluation of a Tool-Less Detachable Power-Assist Prototype for Manual Wheelchairs

Manual wheelchairs are widely used because of their affordability, portability, and mechanical simplicity; however, prolonged manual propulsion can increase upper-limb fatigue and musculoskeletal loading. This study presents the design and preliminary engineering evaluation of a prototype tool-less detachable rear-mounted power-assist system that can be installed and removed without permanent modification of the wheelchair frame. The prototype integrates an adjustable mounting mechanism, dual brushless DC in-wheel motors, passive suspension, and a passive rear-stabilizing mechanism within a single detachable propulsion module. The control lever can be positioned for operation by either the seated user or an attendant, whereas physical attachment and detachment of the approximately 12 kg propulsion module is primarily intended to be performed by an attendant or caregiver without a separate initial fitting procedure. Structural analysis showed a maximum von Mises stress of 126.3 MPa and a minimum safety factor of 1.98 under the specified design loading condition. The mean combined attachment-and-detachment procedure time was 96.06 s. Independent engineering testing with a 120.1 kg test load documented level-ground travel over 55 m at 2.829 km/h and successful traversal of a 10.5° incline (approximately 18.5% grade). During a separate 4-km outdoor evaluation, the GPS-recorded average speed was 2.7 km/h. These results support the preliminary engineering feasibility of the integrated detachable architecture under the evaluated conditions. Further standardized structural, dynamic, comparative, multi-wheelchair, and user-centered evaluations are required to establish practical usability and performance.