Originally Posted by
whburling
what does 559 mean?
This project would probably be helped along a lot if you did some background reading on bicycle wheels - Sheldon Brown, Jobst Brandt, etc...
I started with the bearings...I chose ceramic hybrid technology.
Enthusiasm is a great thing, but for a functional prototype, conventional steel bearings are probably going to be a lot cheaper and easier to work with... it's almost inevitable you'll be ruining some components while getting the ideas sorted out, so pick basic, proven, rugged ones where you can afford to make mistakes.
A wheelchair doesn't sound like a performance vehicle, but
maintainability with widely available components would be great. It happens for example that entry level unicycles use a bearing size that's standard in snowmobiles.