Basically using the sprockets from a bicycle and securing them to the wheel chair hubs should work. The cover could then be secured with pipe or some ...
I've been toying around with this idea for a while. I am living in a studio apartment and they don't like it when I do wielding in my kitchen. Something about fire codes...The idea came from my friend Sean who is in a wheelchair. I made the joke about modifying his wheelchair with a lift kit and some bottom lights but he said he'd rather have something that kept him from getting muddy and wet when it rains. His wheels pick up mud and when he uses his hands to propel himself forward his hands and arms get dirty. Since it rains about 300 days out of the year here I started brainstorming. After many bad ideas I came up with this one. The problem is I can't build it. I have a basic idea for the design and was hoping someone might build it and test it out.
Step 1: The idea
The idea is to add a ratchet-cover like attachment that cups about 1/4th or 1/6th of the wheel on both sides. The cover would probably cover the wheels handles and so would need to have handles itself. The cover would be attached to the ratchet portion which is attached to the wheel hub. The whole thing should ratchet backwards and lock in place so it can be propelled forwards with the wheel. If someone wanted to get fancy they could add a reversible locking mechanism where the user could flip a switch/button and it could ratchet forwards and lock backwards allowing the user to move backwards as well. I thought to keep it simple just allow the ratchet to fall back out of the way and let the user have access to the wheels again.