Step 1: Measure twice... three times.
The first step in this project is going to require some very precise measurements. These plans require bolting two brackets that will hold four bars to suspend the roof over the individual in a wheelchair. Most wheelchairs are designed to be very adjustable, and so the back rest component of my particular wheelchair had several pre-drilled holes which were intended for supporting the backrest and or additional medical gear. If at all possible, you want to use any existing pre-drilled holes for attaching this bracket rather than drilling new holes which may void the warranty of your wheelchair. The location of where this bracket is placed will determine the length of the bars you will need and the over-all dimensions of the canopy you will have to make for the roof of your wheelchair. If the particular wheelchair you are modifying does not have pre-drilled holes, you will have to find a location to drill two holes into the supporting bar of the backrest. It is very important to select this location carefully as you do not want to compromise the strength of the support for the chair's backrest. Also, the metal used on wheelchairs is very strong, and you will need a good drill gun with a sharp drill bit.
In the illustration, the Bar Bracket is labeled and is shown as attached to the wheelchair. This bracket may be attached higher or lower depending upon what works for a particular wheelchair model. Depending upon the height of the individual in the wheelchair and the angle you wish the canopy to rest, the lengths of the canopy bars labeled BAR F and BAR G may change. You will want to measure the Height of BAR F first using a yardstick measuring from the position the Bar Bracket will be attached to at least three inches above the head of the individual who sits in the wheelchair. Keep in mind, you'll want this bar to be at a slight backward angle so that the roof fully covers the individual's head. It is better to add extra height to your measurement then be too short. Keep in mind, the canopy will be made of material and will sag some in the middle. Next, measure how long BAR G must be. You can vary the angle of this bar, which will lengthen or shorted its length. The shorter the bar at any given angle, the more forward sloping the canopy will be. The longer the bar, the more upward sloping the canopy will be. The angle must be taken into account in your measurements. The greater the angle, the longer the bar must be, and the greater the canopy length. You can either measure the angle of this bar with a protractor, or can do it the easy way and take a piece of paper to mark down the angles of the two bars and the length they must be. Work out on paper with pencil first the bar angles and lengths. Next, measure how long the canopy must be given the angle and length of those bars. Once you know the length and the angle of the two poles, you can solve for the length of the canopy using some trigonometry (The first time ever found a use for trigonometry!). Unfortunately, I was never very good at trig, and so I laid out the angles using three yardstick rulers to get the appropriate dimensions and traced the angles onto a piece of paper. If you complete the math calculations, please visit http://www.teacherschoice.com.au/maths_library/trigonometry/solve_trig_sss.htm for how to calculate the dimensions.
Step 2: The Bars.
Once you have determined how long the bars will have to be to support your roof, the next step is creating the bars. There is two ways to do this. First, you can make your own bars. This is recommended in most cases. You may also find bars as I did that were pre-made from hardware store.
The bars consist of a pole with an eye-bolt on each end. The diameter of the eye-bolt you select, and the diameter of the poles will effect the next step of your process, and so I advise reading ahead so that you will fully understand how they will be held by the mounting bracket. The eye-bolts can be attached to the ends of a large dowel if you can find one that is an adequate length. The eye-bolt will be secured by the use of carabiner clips on both the canopy and the mounting bracket, and so the eye hole of the eye-bolt needs to be measure according to the size of the carbiner clip you plan to use. Unfortunately, they come in so many different sizes and styles that I can not recommend a specific size or type. Be careful in pre-drilling the hole on each end of the dowel to screw in the eye-loop. Be sure to properly secure the dowel and use all safety precautions.
The poles that you use must be strong enough to support the canopy. Keep in mind, these poles are going to have quite a bit of weight on them as they will be held out at an angle and must hold the roof on in gust of wind. If the dowels are too small in diameter, you will not be able to drill them on the end to screw in the eye-loops. If the diameter is too big, you will have difficulty making the bar bracket to hold them. Use a hard wood or steel poles.
Step 3: The Bar Bracket.
The bracket that will hold the bars works by creating slots that the poles will slide into and rest. Think of basically a flag-pole bracket that holds two poles instead of just one. This bracket is the most important part and is critical to making precisely correct. You must make two identical brackets, otherwise the canopy will not hang properly when assembled.
To make the bar bracket, you will be sandwiching together the wood in three layers. The two outer layers can be made of thin but strong wood. The thickness of the inner pieces of wood depends upon the size of the bar and the eye hooks you made in step 2. The bars will have to slide in between part B and C and slide between C and D. The angle of these inner parts will vary based upon the angle of the triangle created by the length and angle of the bars.
To determine the proper angles, I suggest sitting the poles you created in step 2 onto a sheet of paper. Make a template like below in Illustration 2 for parts B, C, and D. Cut out these parts and lay them out as they would be if assembled. Will the poles slide out once assembled or is there not enough room for the eye-loops? You want the fit to be snug, but not tight. After positioning the interior parts, cut out a template for part A. Make sure all the parts fit together using the templates before cutting them out in wood.
Keep in mind, you will have to make two Bar Brackets, one for the right side of the chair and one for the left. As there is a right and left side, some things are reversed, so if your cutting out wood, make sure the nicer side of the wood is outward facing. Use your templates to draw out the parts using a marking pen, then use a band saw or other saw to cut the parts. DO NOT ASSEMBLE YET!
Note: You will want to round the corners of these brackets. They will stick out some, and so you don't want to risk injury if someone bumps into the corner of one of the exposed brackets. In place of the eye bolt shown as part E, for mine I drilled a hole into part A for insertion of a lock.
Step 4: Painting the bracket. Measure again.
The one thing I discovered in making this canopy is that no matter how well you measure, your probably not going to get it right the first time. At this point, put the pieces together like a jig-saw and make sure everything fits together. Your going to need to sand, so at this point, if anything does not fit together well, try to sand the parts to get a better fit. You may have to cut again if your cuts were inaccurate.
Next, paint the individual parts. It is easier to paint the parts while it is in pieces then once it is assembled as I learned. You'll never be able to paint over all the visible spaces once it is glued together. Add any decorative touches to the bracket. For me, I painted a Yin-Yang like symbol with flames.
Step 5: Making the canopy.
This is the most difficult and time-consuming portion of this build. You want to make the canopy such that it attaches using clips to each of the four poles in a manner that it is easy to clip on, but does not sag too much. To do this, I suggest laying out the bars for the canopy on the floor at the angle that they will be attached to the chair and measuring again to determine the precise length the canopy needs to be. You do not want to make the canopy to only find out later you made it an eighth of an inch too short.
You can use most any sort of material to make the canopy. I went with a blue vinyl material, though if I had to do it again, I would have picked a lighter material. Ideally, the material should be one that will not let water through in the event that you plan to use the canopy as a rain umbrella as well.
The canopy material should be at least double the size that the canopy will eventually be. You will be sewing two pieces together to make the canopy. In order to keep the roof from sagging inward, you will need two stiff pieces of wire that will be sewn at each end of the canopy. I used thin metal stakes that were intended for garden plants, a heavy wire that does not bend easily, and sewed this such that it would go between where the bars would attach width-wise. This prevents the bars and roof from sagging inward. If you use a lighter material, this might not be necessary. At each corner I attached metal trigger clips that are used to clip onto the loops of the bars.
Note: For my roof, I added additional loops and lots of additional decoration. I sewed pockets for carrying the bars of the roof and a cut-out of flames. I also laced leather around the exterior by first using a hole punch to punch holes around the outside of the canopy roof, then lacing the leather string. This is all optional and time consuming.
Step 6: The Back Pack.
For the back-pack on my wheelchair, I attached several "D" rings in which the canopy could attach to when it was not in use. Mostly for decorative purposes, I also made a belt using leather straps hooked to a large "O" ring for additional support of the roof. This is all optional however.
Step 7: Some assembly required.
I left the assembly for the final step as you will once again wish to lay out all the parts to make sure they fit together before attaching to the wheelchair. When you are satisfied that the bar mounts hold the bars at the proper angles, you can begin to assemble them and attach them to the wheelchair. I highly recommend, first drill screw holes and attach the whole assembly to the wheelchair. Make sure the bars fit into the bracket and that the canopy is held at the right angle. Make sure that the canopy does not lay on the person's head, but is held above their head. Once you are certain all the parts fit correctly, unscrew the bar bracket and use wood glue... then screw it together again. This will add significant strength to the bracket which will be under a lot of stress from the roof's weight.
When you slide the bars into the bar bracket, in most circumstances, they will remain in place very solidly due to the weight. The eye-bolt within the bar bracket can be used to secure the poles such that they can not be pulled out by wind. Simply use a lock or tie the eye-loops of the poles to the loop of the bar bracket. Attach the poles and hook the canopy to the wheelchair, and your all set for a ride in the hot summer sun along the boardwalk or down the street.