Introduction: Design and Assemble a Wheelchair Lever Arm: Assembly Instructions
Full Information for this project:
List of Materials
List of 3D Printed Materials:
(2) Sun Gears
(2) Annular Gears
(2) Double Ratchets
(2) Top Stacked Gears
(2) Bottom Stacked Gears
(6) Planetary Gears
List of Purchased Materials:
(4) 11"x7" Plywood Boards
(2) 17" long cuts of 1/2" diameter PVC pipe
(4) 1/2" PVC 90 Degree Elbow Fittings
(4) 1/2" PVC Tee Fittings
(2) 1/2"x3/4"x1/2" PVC Tee Fittings
(2) 6" Long Cuts of 1/2" Diameter Wooden Dowels
(2) Bike Brakes (available at most bike shops or on amazon)
(2) Single Loop Closed Extension Spring with .047" Diameter, 7/16" x 3-1/2"
(12) Flat Head Phillips Machine Screws #6-32 x 2"
(4) Machine Screw Nuts #6-32
(6) Round Slotted Wood Screws #2 x 1/2"
(2) #19 x 1/2 in. Zinc Wire Nails
(2) 3/4" Tube Straps
Step 1: Attach Stacked Gear to 2 Layers of Wooden Plywood
Using (1) Machine Screw and a screw driver
Step 2: Attach (1) of the 1/2"x3/4"x1/2" Tee Fitting to the Back of the Wooden Planks
Using a power drill to create a hole in the center of the fitting and pushing it onto the back of the machine screw used in step 1.
Step 3: Glue a 3/4" PVC Pipe Into the Top of the Tee Fitting
Secure using a 3/4" tube strap and (2) machine screws. Nail the 6" wooden dowel into the top of the PVC pipe to create a handle.
Step 4: Place a Nail in the Indent on the Left Side of the Ratchet and Create a Small Hole on the Right Using a Power Drill
Size of the whole is dependant on the thickness of your bike brake wire. It should be slightly larger to accommodate the size of the wire easily.
Step 5: Screw the Ratchet in the Center of the Board and Approx. 1" Above the Stacked Gears
Attach the spring to the nail in the ratchet and pull up and around the left machine screw from step 3
Step 6: Attach the Bike Brake to the Bottom of the Wooden Handle and Secure Using the Given Screws
Bike brake should include some kind of fastening mechanism (ex. Screw and Nut) to allow it to be secure on the handle.
Step 7: Attach the Bike Brake
String the brake wire though the hole made on the right side of the ratchet. Once through, clamp the end of the wire using a folded piece of metal to secure the length. Be sure to do this when the ratchet is in its taut position because of the spring.
Step 8: *If Needed* Melt a Small Washer Into the Top of Each Hole on the Bottom Stacked Gear for Additional Support
Depending on the quality of your plastic, you may need to further support your gears with metal.
Step 9: Screw (3) Planetary Gears Into the Washers in Step 9 on the Bottom Stacked Gear
Use the wood screws for added grip and stability
Step 10: *If Needed* Create a Stabilizing Bar and Screw Onto the Back of the Part Using (2) Machine Screw
Create the bar by attaching a 17" long piece of 1/2" diameter PVC pipe with a 1/2" 90-degree fitting and a split 1/2"x1/2"x1/2" tee fitting on each side.
Step 11: Attach to the Wheelchair
Attach the annular gear and sun gear to the wheelchair by unscrewing the large bolt in the wheel, placing the bolt through the sun gear in the annular gear, and screwing the bolt back into the wheel hub. Then line up the sun/annular gear with the planetary gears on the lever arm and snap on the entire assembly