Step 1 - Measure your Childs Physical DimensionsYou will need a tape measure to measure 6 of your childs physical dimensions. These dimentions are entered into the Pipe Length Calculator on the parts list page. The calculator will tell you the length of each pipe segment and the total length of PCB piping that needs to be purchased.
Step 2 -Purchase and Gather Materials and ToolsPurchase the the various parts listed on the parts list page.
Step 3 - Cut the PVC pipe segmentsCut the PVC piping using a PVC cutter or saw, into the various 12 segments that are indicated in the parts list. Remember that the length of these segments is dependent upon the measurements of the child that you've taken. Because so many pieces need to be connected it is important that the cuts are straight and accurate. You can use a hand held PVC pipe cutter or a circular saw.
If using a saw, to save time you can bundle together the pipes such that their ends are aligned with masking tape and then cut them with a single stroke. When cutting the pipe remember to factor in the curf (width) of the saw blade in your calculations so that the length is accurate. Remember to wear safety goggles when using the saw.
Step 4 - Assemble PVC BaseThe PVC fram will be assembled in 3 parts: the base, seat, and the arms and back.
The assembly goes much more quickly if you organize each of the PVC parts into labled piles. You can take a piece of paper and lable it with the number 1-12 and letters A-F, then set the PVC parts on the appropriate labled paper. With the PVC pieces labled you can quickly grab the correct part, as you assemble, rather than sorting throuch a pile of random parts, and then measuring each item to make sure it is the correct length.
Gather the various parts for the base assembly as listed in the following table:
Assemble the pipe segments and connectors as shown in the following figure. Connectors have square annotations and pipes circular.
Step 5 - Assemble PVC
|Seat Assembly Parts|
|Arms and Back Assembly Parts|
Cut the back plate from ¼ inch polyethylene to the outer dimensions of the back seat frame (see step 3). Round the edges with 100 grit. Pre-drill holes centered on the joint (as described in step 1 and shown above) and 8 inches below on each side. Secure using PVC fastener screws.
Remove back plate from gear box. Use pinion puller to remove the pinion gear from the original motor. Trade out the replacement motor pressing the pinion gear on the new motor and reassemble the gear box.
Align the gear box mounting plate to the frame, and fix it using a C-clamp or other type type clamp. You will use the plate as a template to drill out the 4 holes on the frame. Use a #9 (0.196) drill bit to drill the holes.
Now secure the plate to the frame with four 10-32 x 1.5" socket head machine screws and 10-32 lock nuts. Use sadle washers around the pipe on both sides to distribute the force of the screw.
Attach the gear box to the plate using M4 x 10mm bolts.
Insert the hub onto the shaft 1/8’’ from the mounting plate. Orient the hub so the set screw faces the flat face of the shaft. Apply Loctite to set screw and tighten. Using 6-32 x .5” bolts attach the hub adapter and the wheel to the assembly. Be sure to use the outer threaded holes on the hub adapter. Apply Loctite to each mounting bolt. This requires a standard metric hex wrench set.
Cut cushioning foam to size. Use the dimensions of the seat rest area and add an inch to each dimension for foam cutting. Measure out the cover material with an extra 1/4” on each side for the seam and extra 3 inches on top or bottom for a flap. The top section should include the desired height of the cushion on each side as shown in the top right. Sew the cover on the seam lines inside out as shown. Turn the cover right side out and insert foam cushion. Either sew the cover shut or apply Velcro to the flap and secure the cover. Then apply Velcro to the frame and cushion backing to secure cushion in place. Repeat with seat backing base dimensions for the back rest cushion.
Using a wire stripper cut off the end of the Ethernet cable and remove about 2 inches of the outer insulation and separate the small wires. Strip about a quarter inch of insulation off of each small wire. Repeat for both ends of the Ethernet cable.
Note: The Ethernet cable make look slightly different from the cabled pictured above. The Ethernet cable will also have 8 wires instead of 6, two of these wires will not be used and do not need to be stripped.
The next few steps will take the wheelchair to this point by mounting the joystick and routing the cable.
Line up the holes drilled in step 2 and insert a 3/8” sheet metal screw. Push the rocker switch into the panel cutout in the side of the joystick mount. Crimp the two CONN QC RCPT 18-22AWG 0.187 solderless terminals onto the two remaining wires of the Ethernet cable using pliers and push these onto the terminals of the switch. Make sure you know which wires on the other side of the cable correspond to these two wires (although these two wires can be hooked up interchangeably with each other.)
Note: Make sure the slip joint is on the arm piece before attaching the elbow!
Back out the two screws pictured on the left and route the cable as shown. The screws may now be reinserted.
Insert the arm rest into the seat of the wheelchair as shown.
Using a 3/8” drill bit drill a hole at a 45o angle near the bottom of the piece indicated in the picture.
Tape the ends of the wires together and route them through the piece that you just drilled a hole in.
Using a ¼” drill bit drill holes approximately in the locations indicated and route the motor wires through these holes as shown. Curling the tips of the wires slightly can help them pass back out of the pipe through the exit hole. Use pliers to crimp CONN QC RCPT 14-16AWG 0.187 onto the motor wires.
Using a 3/8” drill bit drill a hole in both sides of the electronics project box. The hole should be approximately 1” from the both the bottom and back of the box.
Using the 4” x 1” Velcro strips attach 3 strips of Velcro to the bottom of the electronics box, and apply corresponding strips to the bottom of the battery. Next apply two strips of Velcro to the side of the box as show. These strips will be used to attach the PCB to the electronics box. Lastly apply Velcro as shown to the two base cross pieces shown and apply corresponding strips to the underside of the electronics project box.
Next mount the project box on the base of the wheelchair using the Velcro. Pass the motor wires and Ethernet cable through the holes drilled in the sides of the project box.
The Open Wheelchair hardware design is licensed under CERN Open Hardware Licence v1.2 and the Software is licensed under the GNU General Public License Version 3. By viewing or using the design posted on this website you are agreeing to these licenses. To view the license see our license page.