power-assist unit — mechanical parts

When I took the class “Wheelchair Design and Construction” (ENGR 620) at San Francisco State University with Ralf Hotchkiss and Bob Incerti, each student rode a wheelchair to dinner. For those of us who did not have one, we borrowed one from class. There was only a slight decline/incline — probably not noticeable by most — between the Science building and the Student Center building. Those of us not used to using a wheelchair found the return (incline) a bit challenging — especially after eating!

So one of the things I thought about that semester was a power-assist device (and NOT the kind that walks behind and pushes your wheelchair nor someone else with a power chair that you can hang onto!) I searched on the Web and asked around. These devices do indeed exist but were kind of expensive.

I wanted something that could mount onto ANY wheelchair but was willing to start with anything that will work on the RoughRiderTM that we were making in class. I’ll follow this post with several ideas I’ve tried and ones that I’m still developing. (There are mechanical and electrical parts to my experiments. The portions related to the mechanical challenges will be posted here. The electrical challenges will be posted in the Electronics page.) If you’ve tried to make a power unit or power-assist unit for your own wheelchair, please share your experiences!

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One Response to power-assist unit — mechanical parts

  1. alice says:

    After some research, I realized that “assistance” actually comes in manual forms, too. These include levers that are purchased separately from the wheelchair then attached and geared-wheels that replace the original wheels on the wheelchair.

    The lever-system I tried attaches to existing wheels. The levers engage in a way that allows the wheels to rotate freely (free-wheeling) after pushing the levers to move the wheelchair forward. To slow or stop, the levers are pulled inward toward the sides of the wheelchair. It is also possible to rotate the wheel(s) backward by pulling the levers in- and back-ward. I will not list here the one I tried but current prices are in the $4000 – $5000 range.

    I have not tried geared-wheel systems. These systems also uses handrims but of different size(s) than the original handrims. The advantage of these systems is that “low” gears usually come with an anti-slip mechanism that allows the user to roll in one direction, say up the hill rather than sliding back down. However, depending on the level of the injury to the spinal cord, these type of systems may require more dexterity and/or arm strength than the original wheels. Current prices for these systems are in the $2000 – $2500 range.

    I’ll write more about what I tried in a later post. If you tried one of these systems or a totally different manual (not electric or gas-powered) assist system, please share your thoughts and experiences!

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