I hope this isn't too far off topic. I found this caster wheel that this company is using for wheelchairs built in "low income" countries. Well I would like to try that caster form some projects of my own. I called the company and that don't and won't import any of the wheels into the US so I was wonder if there is any possibility that some US supplier might have something similar. They told me the wheels they use can be 4 or 5" in diameter and are about 4" wide. Only about the center third of the wheel is supported by the hub, the outer section is fairly flexible to conform as it rolls over uneven surfaces. To get a look at it, check out this youtube video. They show the wheel up close at about
1 minutes 7 seconds into the video.
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Also in the video they state that they found the wheel being used on push carts in Zimbabwe.