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The Do-it-Ourselves PVC-X

The PVC-X wheelchair uses the WC-Xframe design to create a wheelchair made primarily with Schedule 40 PVC with hand-held tools.

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The Do-it-Ourselves PVC-X is designed to illustrate that a functional self-propelled wheelchair capable of handling rough terrain can be built with basic tools and locally sourced materials as long as it incorporates a user centric design. It could be built out of other materials such as bamboo, steel, etc.



Institutional/Big Business AT isn't working for people with disabilities in much the world. If it was, then millions of people would not be using antiquated hospital style wheelchairs as their primarily means of mobility.  This should NOT be an acceptable situation, but it is. It is time for us (people who care about this issue) to take matters into our own hands and make the change for ourselves and others who require access to affordable and functional assistive technology such as wheelchairs and other types of mobility equipment.

Active wheelchair users don't just go from point A to B. They need to carry items. They go inside houses and buildings. They travel on both smooth and rough terrain. They have to transfer in and out of their wheelchairs. They engage in work and play using their wheelchairs. Therefore, the wheelchair design must allow for mobility in a wide variety of situations, both in and outdoors.

A wheelchair is a mechanical device. Therefore it requires ongoing maintenance and repairs from time to time. A significant issue in many less resourced countries is the availability of wheelchair parts. In these countries, the most common wheelchair is a cheaply made hospital style wheelchair that is used until it completely breaks down and becomes nonfunctional. Then it is disposed of rather than repaired. These wheelchairs can be purchased in bulk from China at such low prices ($35 per wheelchair) that there is no market for repairing them. 

Developing countries have minimal access to better quality wheelchairs from Europe or the US. When someone is able to acquire such a wheelchair, they are unable to find the specialty parts required for repairs since few can afford to pay for them. Wheelchairs that are made and provided by overseas nonprofits also are difficult to repair due to lack of parts and local repair knowledge.

My approach is that it is an acceptable tradeoff for a wheelchair to occasionally breakdown as long as it can be repaired relatively easily. The economics of less resourced countries is such that imported or manufactured parts are expensive, but certain locally obtained materials and skilled labor are cheap. A wheelchair is a straight forward mechanical device that should be designed to be simple to build and repair by a generally skilled craftsman, when made out of locally sourced materials without specialized equipment.

In developing countries, when cars breakdown, they get repaired. When bicycles breakdown, they get fixed. When wheelchairs breakdown, they too should get fixed (but many times, they don't). The inconvenience caused by occasional repairs, pales in comparison to living the rest of your life using a hospital style wheelchair that is not designed to be independently self-propelled, or having no wheelchair at all (because it broke, can't get fixed, and you can't afford a new one).

The reason I know about wheelchairs in developing countries is that for the past two years I have been supporting SCI in Nigeria and Zimbabwe directly and via the Dubel Disability Foundation which I sponsor and help operate. As a result, I have learned about these problems, first hand.

The WC-Xframe design uses a front trike wheel instead of two front casters in order to handle rough terrain.  In addition, a three wheel WC frame that is not completely symmetrical (has gotten out of whack) is still functional. Whereas, a four wheel WC would be noticeably  negatively effected by a warped frame or imperfect manufacturing. In other words, the WC-Xframe doesn't need to be perfectly made. The WC-Xframe uses the cantilever front supports common to caster wheelchairs to provide leg/foot stability and hand grabbing areas for transfers and upper body stability. The leg frame tubing is placed inside of the Lower Chasis creating a visually more appealing tapered front end to avoid the WC user's legs being splayed apart.

The front trike wheel is as small and as close to the WC user's front feet as possible to reduce the overall length of the WC while still providing rough terrain rollability. The seating uses several inches of dump to increase stability and the pushing mechanics for those that require it (like me). The rear wheels are positioned to optimize self-propel pushing mechanics and dynamic stability via the control of Center of Gravity (COG/wheelie control). 

The following media are Stress Tests that show the prototype PVC-X in action. As more Stress Tests are done, more videos will be created. Please keep in mind that wheelchair performance is the result of the capabilities of both the user and the mobility device.

LIABILITY DISCLAIMER - FOLLOW/USE/BUILD FROM THIS DESIGN AT YOUR OWN RISK!

 

Stress Test#2 - 5 gallons/40 lbs Water Carry for 5 miles on Dirt Path

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Rear Axle Construction

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The PVC-X model shown in the videos is a prototype. I made it to test the concept of making a functional self-propelled wheelchair out of PVC. I am sure that there other ways to produce a similar result since PVC has been shown to be a viable wheelchair construction material. People have been using it for beach WCs for years.

Since the axle connection is an area of high stress, I am using a 1/2" steel rod as a through axle. The rod is connected to the PVC fittings with four 1/2" I.D. x 3/4" O.D. metal collars. Two collars are inserted side-by-side with a metal shim into the fitting as shown in the photos. The thread screw is reversed to move outward when tightened from the inside with an Allen wrench. The axle goes through both fittings on each side of the WC.


The rear WC wheels are held on the 1/2" axle with collars. They are no longer "quick" release. But they do release.

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WC-Xframe Construction

The frame is designed to have as many "boxes" as possible for structural support. I used screws instead of glue to make it easier to change the configuration or replace something that breaks. Gluing is a more permanent solution.

 

A hose clamp surrounds the top of the (cut to fit) vertical axle support 1 1/2" tube, and one goes around the 3/4" horizontal axle fitting for additional strength. If you look closely at the above photo of the underside, you can see the two aluminum cross braces which are bolted on to create a box.

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I am using 1  1/2" diameter PVC tubing for the horizontal Upper and Lower Chasis. The vertical front leg supports and footrest are 1" tubing. 1" tubing is used to allow enough space for the footrests when contained inside the Lower Chasis which creates the Xframe. The tubes are connected with a through bolt.

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Seat/Sideguard Panel Construction

The seatpan, backrest, and side guards are all made of 1/4" PVC sheets. The width of the frame is 15" to fit me. My regular WC is 14". I made this slightly wider so other people could test it too. I like a lot of dump for performance, so there is 4". The amount of dump can easily be customized (along with everything else).
 

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Front Trike Wheel

The trike wheel is 6.5". I put one of my spare pneumatic landboard wheels on a cheap caster frame and secured it to the Lower Chasis with a bracket. In this case, I had to extend fork to make the wheel fit Caster wheels vary widely in size, price, quality, and local availability.

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I have a lot of experience using this size trike wheel on rough terrain. I don't think it needs to be any bigger as long as it can be lifted with a wheelie as needed.

PVC Connectors

There are multiple types of PVC fittings/connectors that can be used. I am using some Snap-on T's for the 1 1/2" tubing. Slip Ts could also be used. Long 90 degree elbows are used for the curves. 1 1/2" to 1" connectors are used on the vertical front leg supports as seen in the photos.

There really are no hidden secrets to the PVC-X design. It is made how it looks like it is made. I think the important aspect is the user comfort and functionality that is created by using the Xframe in the front for the trike wheel rather than the traditional method. 

A CAD drawing will be coming soon. But you really don't need it. I just followed my foam and paper model for the most part.

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Rear Seat Pan Cross Brace

Notice that the top cross brace that holds the back of the seat pan is secured by two cap fittings that have been bolted on to the vertical backrest frame tubes. There are likely other methods for securing it.

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Lifting Straps

I added two bolted on 2" nylon straps to aid lifting/carrying by helpers.

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