People can wheel themselves along in wheelchairs by grabbing handles affixed to the wheels. One must have an upper body capable of such a maneuver. If you don't, and have no-one to push you, the option is to put feet on the floor and walk along in tiny steps, pulling the chair forward with the power of flexing the lower leg.
This is really not an optimal motion for propulsion. Better would be to turn around and push off backwards with both legs, extending the leg. But then you are going backwards and there is always something in the way.
The BUNGCO Watchspring wheelchair employs this natural push-off leg extension motion to wind the springs, which can then be used for forward propulsion. Engaging a hand brake on each side allows the spring to be wound on pushing back the chair. The chair is geared such that a short distance of going backwards will then be parlayed into a long distance of forward propulsion as the spring discharges. The chair occupant can steer using the hand brakes on either side.
The encased springs are the diameter of the wheels and fit neatly beside them. The all-clockwork mechanism means these chairs will still work when the lights go out, temporarily or for good.
It should be noted that although some prototypes of the watchspring wheelchair were alarmingly fast, those distributed by BUNCGO to the VA move at a steady, sedate and dignified pace.-- bungston, Mar 21 2017 You're kind of missing the point of a wheelchair. This design uses the legs to push back and wind the springs. Where-as, most wheelchair users are in a wheelchair because they CAN'T use their legs.-- neutrinos_shadow, Mar 21 2017 I like the idea of storing motive energy in a spring though. Maybe braking can wind the spring. (+)-- 2 fries shy of a happy meal, Mar 21 2017 How about either bicycle-style pedals (for people who have some use of their legs, but can't walk), or hand-crank pedals (for people with arm strength but no leg usage)? The pedals could even be used to wind your springs, so that the user could build up enough stored energy for a quick sprint or a steep hill.-- MaxwellBuchanan, Mar 21 2017 It could also have an autonomous navigation system for those who don't know where they want to go. In fact, it might be simplest to just leave the person at home and let the wheelchair go about its business unencumbered.-- MaxwellBuchanan, Mar 21 2017 Though it would require external persons to power it up, couldn't you just put a large winding key on the back ?-- FlyingToaster, Mar 21 2017 /most wheelchair users are in a wheelchair because they CAN'T use their legs/. A fair # of people can use legs but cannot reliably support their weight for distances.-- bungston, Mar 21 2017 random, halfbakery