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Fitting the seat and back upholstery for a wheelchair rider is the final step in making a customized wheelchair. You can reduce the outside width of the chair, and the rider will travel much more freely if the upholstery is no wider then necessary. This chapter describes how to make long lasting upholstery at a minimum of cost. |
Although many different materials have been used for wheelchair seats, including cane, wood, and metal, we have chosen a sling seat made of heavy canvas. All seats can cause pressure sores unless they are used with an adequate (usually thick) cushion. We prefer sling seats because they conform somewhat to the shape of the wheelchair rider's bottom. With a sling seat, many people can use a thinner or softer cushion without becoming uncomfortable or getting sores. Once a pressure sore develops, the wheelchair rider must remove the pressure immediately to avoid a serious medical problem. Wheelchair riders who have a spinal cord injury or other disability that limits sensation must take special care. Healing can be slow, and a tiny irritation can quickly become a deadly infection. Pressure sores have killed many disabled people, including one of our fellow wheelchair builders, because the prevention and treatment of the sores were not taken seriously.
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Flexible seat materials stretch with time and use. As the fabric sags, the design of many wheelchairs forces the rider's weight to press on the metal seat support tubes. Even with a cushion, discomfort or sores usually result. The ATI-Hotchkiss chair unfolds, widening further and further to take up the slack as the canvas stretches, until the seat guide hooks hit the axle sockets. Do not make the canvas seat so wide (and the seat tubes so low) that the seat hooks can not move down any further. See the chart in Chapter 4 for maximum seat widths. |
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MATERIALS
| ITEM | QUANTITY | PART OF CHAIR |
| Heavy canvas, cotton or synthetic | 6' x 3-1/2' (183 cm x 107 cm) | Seat and Back |
| 1/16" x 1/2" steel bar (2 mm x 12 mm) | 4 pieces, 16" (40.6 cm) long | Edge Bars |
| #12 sheet metal screws | 8 screws, 3/4" (19 mm) long | Seat Back Screws |
| 3/16" (5 mm) fine thread bolts and locknuts | 8 bolts, 1-1/4" (3.2 cm) long | Seat Bolts |
| Thread or cord* | 24 yards or meters | --- |
| Leather or waterproof imitation leather** | 3' x 20+" (91 cm x 51+ cm) | Protective Covering |
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* Neither machine nor hand stitching will hold up if the thread is not strong enough. Finding good quality thread has been very difficult in some countries, especially if the thread must be used in a sewing machine. The thread must be very tightly wound and must be strong enough that it is difficult to break by hand. If the best machine thread available is still too weak, a heavier hand stitching cord may be the only alternative. ** A single layer of waterproof imitation leather or genuine leather can help prevent the canvas from wearing out. In most countries imitation leather is cheaper than genuine leather; however, it can be hot and sticky and increase the chances of some people getting pressure sores. In any climate, genuine leather or plain cotton canvas is the best choice. |
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TOOLSWe have used three types of sewing tools successfully: an awl with a needle and thread, a stitching awl, and a heavy duty sewing machine. We have designed the upholstery so that it can be made with a minimum amount of stitching; it should take no more than an hour to stitch a set of upholstery, even if you are using a hand stitching awl. |
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DIRECTIONS
The seat back upholstery and the seat upholstery are made in the same way. The following directions describe how to make the seat and seat back upholstery when the length of the seat is the same as the height of the back. If the seat back is longer or shorter, adjust your measurements accordingly. When installing the seat back, set it very high on the chair frame tubes. The top of the seat back should always come very close to the push handles.
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1) Measure and cut the canvas. The canvas should be twice as wide as the seat will be plus 1-1/2" (38 mm) for the seam. For an extra stong seat, the canvas should be twice as long as the length of the seat (or height of the back). If you do not make the canvas twice as long as the seat (or height of the back), be sure to cut the fabric at least 8" (20 cm) longer than the length of the seat in order to add reinforcement to areas that usually wear out first (the front of the seat and the top of the seat back). 2) Sew each piece of canvas into a tube by folding the fabric in half and sewing a 3/4" (19 mm) seam along the open edge. Iron or fold the seam so that all the seam material lies to one side. |
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3) Turn each tube inside out. Tuck the excess length into the ends of the tube.
4) Arrange the material so that the seam is an inch or two (3 - 5 cm) from one edge. The extra hem material should point away from the edge. Don't put the seam in the middle where it could press against the spine or tailbone, causing pressure sores.
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5) Sew a 1/4" (6 mm) seam along the front edge of the seat canvas and along the bottom edge of the seat back canvas. The seam will keep the canvas from shifting. Leave the other end open to make it easy to insert the edge bars. MAKING THE EDGE BARS 1) Cut the two seat edge bars and the two seat back edge bars. The edge bars are made from 1/16" x 1/2" (2 mm x 12 mm) steel bar. A standard chair uses four 16" (40.6 cm) edge bars. If the chair you are making has a shorter or longer seat back height, you will need to adjust the measurements accordingly. |
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2) Using the seat support tube drilling jig with the edge bar insert, drill five 3/16" or 7/32" (5 or 6 mm; the larger size for easier assembly) holes in the seat edge bars and seat back bars.
Place a seat edge bar in the channel of the wooden edge bar drilling insert, and slide them into the drilling jig until they hit the stop bar. Both the edge bar and wooden insert will stick out from the drilling jig on one end. Clamp the insert securely to the jig using two C-clamps as shown. Place it on the drill press table and drill all five holes. Repeat the same procedure with the other seat edge bar.
The jig will space the holes as shown in the diagram. A #12 sheet metal screw should slide freely through the holes in the seat back bar.
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ASSEMBLING THE SEAT AND SEAT BACK1) Insert the edge bars into the upholstery so that the holes closest to the ends of the edge bars are positioned on the top of the seat back or toward the front of the seat. Be sure the bars don't catch on some of the inner layers of canvas. Once they are properly positioned, poke holes in the fabric by pushing a scribe through the fabric and into the holes in the edge bars. The basic seat or seat back is now finished. |
2) If you wish to add some decorative or protective covering to the upholstery, cut a piece that is big enough to wrap around all four edges of the canvas. Sew, rivet, or glue it in place. Some wheelchair makers have used contact cement to hold leather in place while sewing. This works, but the glue is dangerous to breathe or touch over a long period of time.
When using contact cement, have plenty of fresh air. Do not apply the glue with your bare hands!
3) Attach the seat to the seat support tubes with 3/16" (5 mm) bolts and nuts.
4) Attach the seat back to the back frame with #12 sheet metal scews.
