Introduction: PPAT Team Jim
Jim is a man who lives in East Boston and is a power wheelchair user. When he was young, he suffered a spinal chord injury that has since then limited all of his lower body and much of his upper body movement. Much of his movement is limited, but he is mostly independent and can communicate effectively. One of his favorite hobbies is playing power wheelchair soccer alongside his team, the Boston Brakers. Because his daily wheelchair is different than his soccer wheelchair and it's a hassle to switch from one to the other, he rarely uses both wheelchairs on any given day. His daily wheelchair has a customized table attached specifically for his use, but since both wheelchairs have different armrest widths, attaching it to his soccer chair is not possible, leaving him without a table on days he plays soccer. Our team developed a new lighter table that is able to hold all his gadgets, is more protective of his essential gadgets, and most importantly, is adaptable for both wheelchairs' armrests.
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Step 1: Bill of Materials
The following link is of a spreadsheet of a bill of materials as well as contains links for each part, how to search for it, and how to purchase it
Furthermore, here is the link to the Github page where you can find the Solidworks Part and Assembly files that were used to make the drawings below:
Step 2: Tools
For this project, you will need the following machines and tools:
Mill, bandsaw, drillpress, belt sander
File, sandpaper, screwdriver / drill, scissors, hammer, 10-24 and 8-32 tap
Step 3: The Table
The table's shape (shown below) is cut with a few tools, described in the following steps. The piece with the armrest is the 'main table', the thin piece is the 'side wall', and the end piece is the 'outside table.' If the polycarbonate has a protective layer on it, do not remove until the end as you can use it for markings.
1. To cut the pieces, bandsaw polycarbonate to approximately the straight dimensions shown in the pictures, including the inner 3in-radius fillet in the main table.
2. Using a belt sander, sand off the corners to approximately the 1/4in and 1/2in fillets shown around the tables.
3. Using a small end mill (max 1/8in diameter), mill the rectangular slots of the three sections; use a size #7 end mill to drill out the holes in their corresponding location on all three tables.
4. On the bottom of the table (not highlighted in the CAD drawing), drill 2 #24 holes 3/4in apart, 1/8in deep for the hook to screw into. Use a 6-32 tap to tap the holes, but don't screw in the bolts just yet
5. If desired, drill a hole on the side of the table for straw use
6. Screw in the hinges to the three pieces of the table using the 6-32 3/4in long screws and 6-32 nuts. Use locktite to secure them
Step 4: The Armrest Holder
The completed table will not be able to sit on the armrest without a holder to support the weight of the gadgets and the table end itself. The next steps and images will describe how to make the table holder bolted to the armrest.
1. Detach the clamps that would normally hold the phone from the selfie-stick with a hammer and pull off the rubber covering
2. Adjust the spring of the clamps according to the width of the armrest. You may not need to adjust it if the armrest is less than 3in in width
3. With a 5/8in endmill, mill a 2.75x7in white ABS piece to a height of 1/4in; this will be the cover. Use the #18 drill bit on the mill to drill out the 6 through-holes. Chamfer the 6 holes so the flathead screw are flush to the ABS piece when screwed in
4. Mill a 2.75x12in white ABS piece to the U-shape shown above, this will be the attachment piece. Continue to mill down the bottom right corner of this part as shown in the drawing. Note that the 6 top holes for the attachment are not through-holes, but rather tapped holes to attach the cover. Mill out the holes to a depth of 3/8 of an inch
5. Carefully mill the 12 inch piece with 3 sets of holes on the slot walls; these holes will provide a method of adjustment by allowing the user to pin in the table at different distances from their body. The 10-24 3in bolt will be used as the pin
** Make sure the inner wall (aka the side to were the table lays) is drilled with a #25 bit and tapped with a 8-32 tap, and the outer wall (aka the wall that is furthest from the user) is drilled with a #7 bit for the pin to simply slide through.
6. Use the bandsaw and drill press to cut and drill the shape of the .0625in thick aluminum to the dimensions shown. Make sure to file edges and corners to remove sharp ends
7. Bolt in the aluminum plate below the attachment piece using 8-32 bolts, and bolt down the cover to the top of the attachment piece using 8-32 1/2in flathead screws
8. Attempt to test the attachment mechanism by inserting the table and inserting the pin. If the pin is unable to pass through both the attachment piece and the table holes smoothly, try drilling a size slightly larger, but make sure the holes do not interfere with other mechanisms or break the already-thin table
9. Repeat steps 1-8 to make holders for different-width armrests
Step 5: Water Bottle Holder
This is a piece that will attach under the table to hold the water bottle. It's assembled as described below:
1. Cut out a 2.5in x 2in block of the remaining 3/8in thick polycarbonate, and drill the holes as instructed in the drawing
2. Cut out a 2.5in x 6in sheet of the .093in thick polycarbonate, and drill the holes / bandsaw the slit as instructed.
3. Screw the thin polycarbonate onto the side of the thicker one carefully with #8 wood screws while making sure the hook is already threaded through as shown in the picture
4. Bolt the thick polycarbonate with the clearance holes for the table onto the bottom of the main table using 6-32 bolts, making sure the bolt goes through the hook holes as well
5. For the cup pouch, cut off the original handle. Loop a strap as shown above and close the loop with a safety pin
Step 6: Finishing Parts
Once you have all the parts cut, milled, and drilled, feel free to sand / file / remill parts down to preference. Be careful not to drill through any threads.
Additionally, to secure the armrest attachment, Velcro can be used in addition to the spring-loaded clamps. The Velcro can be wrapped around the armrest and attached tightly so that the table's own weight does not tilt it downward. Additionally, Velcro can be attached behind the cup holder wall such that it can hug the cup in and prevent it from tipping.