This project is designed for people who need to use a wheelchair to get around for long periods of time but don't want to hold onto their drinks themselves.
The required materials are: a wheelchair, a 3D CAD program, a 3D printer, bolts, and wingnuts
Step 1: Get the Arm Measurements
First you will need to find the diameter of the arm that the cup holder will be attached to. In my case it was 3/4 of an inch
Step 2: Starting the Model
Next you need to start designing the model in whatever CAD program you are most comfortable with. I used the program Onshape for my design. You will want to create a rectangular base for starting the back of the cup holder. Use whatever dimensions you need for this step. Mine is 4.25x2x1 inches.
Step 3: Adding the Notch
For this you will need to make a half circle extrude on the base you made earlier. Use the diameter of the arm you found earlier as the diameter of this circle.
Step 4: Adding the Bolt Holes
Now make two holes that cut through the entire base of the model positioned near the edges with a diameter slightly above the diameter of bolt you want to use. It is important to make it slightly larger so that errors with printing won't mess up the holes. I positioned my holes .5 in from the top and .5 in from the sides
Step 5: Creating the Second Base
For this step you should create a duplicate of the other file to start the other side off of. This allows you to not need to repeat the other steps.
Step 6: Creating the Block for the Hole
For this you want to make an extrusion attached to the side of the base that doesn't have the notch so that you can put a hole for cups to go into. Make it whatever length you want, I made mine 3.5 in for a total length of 5.5 in.
Step 7: Creating the Hole
For this you want to make a hole that the drink will go into once the holder is printed. The diameter should be just above the diameter you expect to need for the drinks. In my case I made it just above 3 inches, the diameter of a soda can
Step 8: Printing the Files
Once that step is done you can take your files and upload them into whatever program you use for 3D printing them. Then you pick the quality of print you want and start the print.
Step 9: Putting It Together
Now that the files have printed you just need to line up the notch with the arm you want to attach the holder to and slide the bolts through the holes. Then attach some wing nuts to secure the two sides together
Step 10: Enjoy
Now you just need to put your drink of choice into the cup holder and enjoy.