David,

In my mind a redesigned wheelchair needs these key features:

Low cost of manufacturability, high level of durability, easy of repair if necessary, light weight, folds flat for easy transport/shipping to far places, flexibility for multiple types of terrain, and ability for gear reduction for going up hills easier.

I would look at a simple folding chair (the kind that comes in a bag) as a starting point for the frame work of the unit, with a nylon type seat/sling in the middle to support the rider. Since some of these folks may be in the chairs 24/7 comfort also has to be critical. A frame structure like a bag-chair will also allow it to be light weight, fold up flat, and can be extremely durable if the structure/connection points are designed properly.

The points where the wheels attach (wheel ends/spindles for lack of better words) can be made of a glass filled reinforced nylon (Nylon-66) or similar low cost but high strength material. I would incorporate a molded in place wheel spindle/axle with quick disconnect wheels for easy shipping and maintenance if necessary.

The wheel assembly is where the critical feature of the wheel chair comes into play. A simple conventional wheel can be designed for use in areas that rocky/uneven terrain isn’t an issue. But for areas where the terrain is an issue I would design a composite/plastic wheel that has a secondary wheel on the outside that is slightly smaller, has a handle/knob on it (like a suicide knob for lack of better words), and is gear reduced through a one-way clutch mechanism for climbing hills. I would incorporate an anti-roll back feature into the gear reduction/one way clutch to help climb hills or use as a brake coming down hills.

I would also try to incorporate as many off the shelf parts as possible, like common tire sizes, tubes, bearings, or other parts in order to keep the cost low and help with replacement parts in the future (think of small block Chevy……parts from the 60’s work all the way through the 90’s if you need to MacGyver something together in the middle of Haiti).

As for cost I would think you could engineer it here, have the components made by a low cost country (China), and final assembly in the states. The seat can be made for less than $1 - 2 in fabric, $3 - 4 for the rods for the structure, $3 - 4 for the rod ends, $7 - 8 each for the wheel ends/spindles ($15 total), $10-15 each for the wheels ($30 total), and $15-20 for the gear reduction mechanism ($40 total). Add in a few $$ for odds and ends and you could have something for less than $100………..probably half that number when you get into the 100K volume number.

Like you said earlier………..you need to think totally out of the box and take as many ideas as possible and melt them together into something spectacular.

And when you get frustrated and think it might be a monumental task take a look at the web site below:

http://www.bodynbobsled.com/

Almost 20 years ago Geoff Bodine (former NASCAR driver) was approached by the USA bobsled teams looking for help. They told Geoff about how they competed on old equipment that they had to buy second hand from the European teams. Geoff set forth on a mission to design and build the best equipment here in the US for our men and women competing for our country. After almost 20 years the US men’s bobsled team won the gold medal at the Olympics in a Bodine bobsled, finally fulfilling Geoff’s vision and goal he had been working for over the last 18 years.

Having worked in a few third world countries myself, I fully understand the need for "affordable" and that would be a prime factor for me. Parts that would interchange with commonly existing chairs, would sure come in handy in those kind of places. You know how ingenious desperate folks can get when it comes to working with what you have available. A new high tech chair is great, but how about if those new wheels or axle's could retro fit the more common chairs currently in use out there as well? Perhaps a good repair facility to improve, rebuild, upgrade existing chairs would also be of great benefit in the immediate future?

Speaking of Haiti, I just saw a news blurb about some 6,000 amputee's as a result of the recent earth quake. Housing today, wheel chairs tomorrow.

slider701,

You bring up really great points. I was thinking of using an alternator bearing for the wheel bearings. They are made by the millions and millions and they are available all over the world for not much money and they take a terrific beating. I hear wheel bearings is a huge problem in chairs. We just have to keep thinking about making everything as bullet-proof as possible.

I think the chair will have to be made from steel. Steel can be welded anywhere in the world for a repair. Plastic becomes much more difficult to repair.

I have thought of making a monocoque chassis for the chair. I have also thought of using our CNC tube bender to see if we could make the chair from less tubes to make it stronger and easier to make.

I too wanted a gear reduction of some sort when I was out wheeling around. The problem is weight and cost.

Ernie,

You bring up some good points. They have to be able to service the chair in a reasonable way if it does break.

David
:):):)

You are a good man David Kirkham.

Just my thoughts and I really admire you and your efforts btw,

Take a look at outdoor or jogging prams for some inspiration, simple triangular tublar frame design, maybe use bigger rear wheels 26" mountain bike wheel should be fairly cheap to source and durable, you can get 26x1.0-1-5 high PSI (100) slick puncture resistant tyres from many bike tyre manufacturers (continential do a particluary good one) who may be interested in your charity effort.

The more the "cog" is toward the rear of the chair the eaiser it is to lift the front and manoevuer, obviously this requires a level of balance and expertise from the user to learn and get right.

Will they need purchase rings attached to the wheels rims to push the chair, I assume the main reason for these rings is to stop picking up debris & dirt from the road via the tyres but not sure how much they actually add to the controlability, weight etc. Otherwise you'll be suppling a pair of gloves with every chair in fact not necessarily sure having the rings reduces this requirement given the impact on the hands anyway.

Smaller optionally fixed or turning pivot 16" or 20" BMX front wheel to give manoeveurbility when required

They also know how to make these things collaspable.

example here http://www.babyjogger.com/joggers_strollers.aspx

I'm out in the middle of the forest mountain biking. Thinking about how tough it would be riding a trail on a wheelchair. What about using a hub from a three speed. I think they have 7 or 8 speeds now.

Doh, it just hit me that the other side would have to go the other way. Wonder if it could easily be reversed? Kinda takes away from the off the shelf solution though.

Phenominal David. What a great cause. And, it would appear history is now repeating itself. Under the Hurlocks, wasn't it AC Cars that made motorized invalid carriages for the British government during the 50s and 60s?

Bob McMahon

Take a good look at the "athletic" wheel chairs that the para-olympians use. Many solutions may be out there already, they just need to be consolidated into a SUV of wheelchairs vice specialized ones for basketball, hammer throw, marathon, etc.

Also, incorporate wheelie bars! Prevent those who are in them from tipping over backwards, and those of us borrowing their grandmother's chair and showing off from ending up in one....