Center for International Rehabilitation

MAKING THE X-BRACE HALVES

The x-brace supports the seat and allows the chair to fold to a width of twelve inches (30.5 cm) or less. This is an important feature for riders who wish to fit their chair in the aisle of a bus, pack it on the side of a donkey, or throw it in the trunk of a car. If the x-brace is well made, it will also give the chair some flexibility, allowing all four wheels to remain on the ground while riding over uneven terrain.

Each x-brace half has four basic parts:

1) the seat support tube,

2) the guide hook (it attaches the seat support tube to the back of the frame),

3) the crosspiece (square tube) and reinforcing washers,

4) the bottom tube (which slides onto and rotates around the sideframe).

MATERIALS FOR ONE X-BRACE (TWO HALVES)

ITEM	QUANTITY	PART OF CHAIR
1"O.D. tubing	2 pieces, 16" (40.6 cm) long	seatsupport tubes
1" O.D. tubing	2 pieces, 6" (15.2 cm) long	bottom tubes
3/8" (10 mm) solid steel rod	2 pieces, 6" (15.2 cm) long	guide hooks
3/8" (10 mm) I.D. washers	4	reinforcers
1" square tubing*	2 pieces, 17" (43.2 cm) long	crosspieces
* 17" is a typical length for the crosspieces. Crosspiece length will vary according to the width and height of the seat. Chapter 4 includes a description of how to determine the appropriate seat width and height for a customer. Chapter 4 also includes a chart that lists the lengths of crosspiece tubing that are appropriate for wheelchairs with different seat widths and heights.

JIGS USED TO MAKE THE X-BRACE HALVES

Seat Support Tube Drilling Jig
X-Brace Welding Jig
Crosspiece Drilling Jig

The jigs can be purchased as part of the Basic Tool Kit; they can also be made locally by following the directions in Appendix B.

DIRECTIONS

1) Set up the Hossfeld style bender to bend rod, using the U-pin roller mounted on the center pin as a 1-1/16"

(2.7 cm) die. See Chapter 6 for more detailed instructions on setting up the bender.

2) Begin by making the two seat guide hooks. Cut two 6" (15.2 cm) lengths of 3/8" (10 mm) solid steel rod. Round off both ends of the rod on a grinder.

3) Position the rod in the bender so that the tip of the eye bolt bending dog touches the rod about 1/8" (3 mm) back from the end of the rod. Tighten the thumb nut and bend each piece of rod 180° as shown. Compare this bent hook to a finished sample.

4) Cut two 16" (40.6 cm) lengths of 1" O.D. tubing for the seat support tubes. Place them in the hole drilling jig. Drill five holes all the way through each tube. These holes will be used to attach the seat fabric. (Directions for making the hole drilling jig are found in Appendix B.) Scribe a line 8-1/4" (21.6 cm) from the front end of one tube and from the back end of the other tube. The front end is the end with a hole drilled 1/2" from the end of the tube.

5) Cut two 6" (15.2 cm) lengths of 1" O.D. tubing for the bottom tubes. Scribe a line 3-1/4" (8.3 cm) from one end of each bottom tube.

6) Cut two 17" (43.2 cm) lengths of 1" square tubing for the crosspieces. Using an 8-inch half round file or a shaped grinder, file both ends of each crosspiece to make a trough 1/4" (6 mm) deep as shown. Pinch the ends of the crosspiece tubes so they fit snugly against the round sides of the seat support tubes and bottom tubes.

NOTICE: SEE NEW JIG DESIGN.

The following diagrams show the welding of the x-brace on a jig made of plywood. This type of jig must be protected with sheet metal to keep it from burning up when the seat guide hooks are welded on. Our newer design of an all-metal jig will last longer; it is described in Appendix B. Both jigs work the same way; the following instructions apply to either the plywood or the all-metal jig.

7) Place the seat support tube across the top of the x-brace welding jig. The front end of the seat support tube should be on the left side of the jig (see drawing on page 67). Place a crosspiece tube in the jig to the right of the vertical block as shown. The left edge of the crosspiece tube should be in line with the mark on the seat support tube.

8) Slide a 12" (30 cm) long piece of sideframe tubing (7/8" O.D. or equivalent) into a bottom tube of the X-brace (the 6" [15.2 cm] length of 1" O.D. or equivalent tubing). Place both on the jig, clamped against the bottom tube support blocks as shown. Align the mark on the tubing with the left edge of the crosspiece tube.

The jig has been made for a 17" (43.2 cm) crosspiece. If you are making a longer x- brace add enough 1" (2.54 cm) wooden spacers between the bottom tube and the support blocks to adapt the jig to the desired length. If you need to make an X-bace with 15 or 16" long crosspieces, rebuild your jig by connecting the bottom tube support blocks 1" or 2" closer to the other end of the jig.

9) Before clamping all the tubes in place, be sure that the holes in the seat support tube are at the correct angle. Put a drill bit through one of the holes in the seat support tube. Sighting along the drill bit, adjust the tube until the drill bit is parallel to the slanting block mounted near the middle of the jig (see the diagram).

10) Clamp the tubes securely in two directions (to the jig board and to the wooden blocks).

11) Place a guide hook on the right slanting block as shown. Put a 7/8" diamter tubular spacer (or a metric equivalent of the diameter of the sideframe tube) between the end of the seat support tube and the hook. Push the hook toward the seat tube until it bumps against the spacer block. Clamp it in place with the washer and nut. (When making the other x-brace half, the back of the seat support tube and the seat guide hook will be on the left side of the jig.)

12) Braze the two ends of the crosspiece onto the seat support and bottom tubes. Tubing tends to warp when it is heated and cooled on only one side. If these pieces warp, the chair is likely to be poorly aligned, difficult to push, and difficult to fold.

To prevent warping, use the T-joint brazing technique that follows. Do not get the steel tubing any hotter than is necessary to melt the brass.

13) T-JOINT BRAZING

a) Tack the joint on either side.

b) Starting on one side, braze from the tack up to the center.

c) On the other side, braze from the tack to the center.

d) Turn the piece over and repeat the same procedure.

e) If there is some warp in the tubing, heat the opposite side of the tubing to a very dull red and let it cool. This should help to straighten out any warping.

14) Remove the first x-brace half from the jig and make the other x-brace half. Put the seat support tube with the front end on the right side and the seat guide hook on the left side. Other than this change, set up the jig exactly the same.

15) Place one of the x-brace halves in the drill press vise. Lay the crosspiece drilling jig on top of the crosspiece. Center the hole and drill all the way through the tubing. Repeat this procedure on the other x-brace half.

16) Weld a 3/8" (10 mm) I.D. washer around both sides of the center hole in each x-brace half. After welding the washers on, bore only the outside hole of each x-brace half to 7/16" (4.5 mm). This will give the chair some added flexibility. (The outside holes are on the same side as the short ends of the end tubes.)

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