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.
Stress Test#2 - 5 gallons/40 lbs Water Carry for 5 miles on Dirt Path
Rear Axle Construction
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.
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.
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.
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).
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.
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. You can buy one on Amazon.
UPDATE: Since creating the PVC-X, I have made different versions. You can make a hybrid wheelchair using a 5" x 1" solid rubber wheel. This wheel does not vibrate on smooth surfaces at higher speeds like the 6.5" x 2" does.
Buy at Home Depot.
Buy at Amazon.
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.
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.