New Scientist has a great interview with Ralf Hotchkiss, who's working with engineers and the disabled in the developing world to design wheelchairs that're cheap, will work on unpaved roads, and can be repaired with local materials. Cool stuff:
"What are the essential things to consider when you are designing a wheelchair?
"Weight and cost are crucial. The chair I'm sitting in now, which is one of our Whirlwind designs, weighs 12.5 kilograms and costs between $100 and $200, depending on where it is made. Compare that with a chair from a typical manufacturer in the west which weighs around 21 kilograms and costs $1000. Our newest chair is lighter than even the most expensive aluminium chairs, though ours is made using the cheapest steel tubing. This means the chair can be repaired easily by the local blacksmith with the same tubing that is used for restaurant chairs.
"Our wheelchairs also fold, which is crucial if you are travelling on public transport. If you are going from town to town on buses in Africa or south-east Asia they will charge triple to take you and a non-folding chair.
"The new Whirlwind chair also has a longer wheelbase than the older models so it can go down a much steeper slope without tipping over. Tipping forwards is the leading cause of injuries among wheelchair users. If an automobile had its centre of gravity as high as a wheelchair it would be three storeys tall - touch the brakes and over it goes."