Long-Range Wheelchair Attachment for Off-Road Terrain

Kyaro Assistive Technology is an NGO based in Arusha, Tanzania. They work to provide assistive devices to local communities by building wheelchairs, physical therapy devices, splints, walkers, etc. using local material and labor. Since 2023, they’ve distributed 1,331 assistive devices including 705 wheelchairs, 57 standing frames. We have been working with Kyaro Assistive Technology for the development and testing of a wheelchair off-road attachment designed to improve mobility over rough terrain while maintaining ergonomic efficiency. Our prototype features a lever-actuated system that enhances force transmission, enabling users to navigate inclines and uneven surfaces with reduced exertion. The attachment consists of a front-mounted freewheel, a chain-sprocket system transmitting power to the wheel, and an 18-inch lever arm, designed to provide a mechanical advantage greater than one, thereby amplifying the user's input force. The system is modular, with a “shish-kebab” (sequence of components on a single axle) assembly that allows for easy disassembly and component replacement, ensuring durability and manufacturability in resource-limited settings such as Tanzania. To validate our design, we conducted force transmission testing using free weights and a force gauge, lever ergonomics testing with user surveys, and terrain testing on unpaved paths. Mechanical advantage testing revealed an average experimental mechanical advantage of 1.116, compared to an idealized value of 1.57, with sources of error attributed to alignment inconsistencies, attachment stability, and system efficiency losses. Ergonomic testing aimed to assess comfort and sustainability across different lever geometries. Terrain testing evaluated durability and component stability under real-world conditions. Our findings suggest that while the design effectively increases force transmission and provides an intuitive user experience, material improvements and assembly refinements are necessary to enhance reliability. The results of this study contribute to the development of cost-effective mobility solutions for individuals in challenging environments, offering insights into the optimization of assistive technologies for off-road wheelchair accessibility.