Winter Wheelchair
Objective
According to USA.com, New Hampshire is the third snowiest state in the U.S. Unfortunately due to the limited design of most wheelchairs currently on the market, this makes life harder for wheelchair users living in New Hampshire. My team set out to design a wheelchair that could move efficiently through high layers of snow.
Technical Details
For this project, cost was a huge factor as we had a budget of only $500. Guided by research, we weeded out some early ideas and decided to run with two cost-effective options: treads and levers. Treaded wheels would provide extra traction between the wheelchair wheels and ice/snow. The bulk of the project would lie in designing a lever mechanism for the wheelchair.
Our first prototype was based on the bicycle chain. By pushing or 'pumping' a lever back and forth, the user can increase the speed of the wheel. Our second prototype allowed us to test other aspects of the lever mechanism, especially how the levers were able to overcome friction.
Results
We discovered that the position of the users hand (along the lever) changed not only speed, but also torque. Positioning the hands closer to the top of the lever generates more torque (opposition to friction) but less speed, and positioning them closer to the bottom generates less torque but more speed. Depending on the terrain, wheelchair users will be able to adjust the position of their hands.
We anticipate that with a higher budget the final version of our wheelchair could have fully treaded tires, levers (whose lengths can be adjusted), a gear system with a derailleur, and of course, a footrest.