Today I’m making a backpack for my friend Jayy’s companion robots.
Here are all the supplies you’ll need if you want to make this project yourself:
- Heavyweight fabric, I used both cotton canvas 10oz and 1000 denier ballistic nylon
- 1″ nylon webbing
- 1″ buckles (2)
- D-rings (2)
- Swivel clasps (2)
- Zipper (optional)
- Grommet kit (10mm)
- Fabric scissors
- Sewing machine
- Sewing needle
- Sewing pins and/or clips
- Thread snips (optional but handy)
- Thin upholstery foam (for strap)
- Printer with paper (for pattern)
- 3D printer
- PETG filament
This project is sponsored by Digi-Key, where you can find a surprisingly large variety of scissors, in addition to all your robot-building supplies.
Making the First Prototype
I whipped up a first prototype designed around a round drawstring compartment for the robot. I printed out the pattern and cut out the pieces from black canvas– it’s heavy-weight enough to simulate the final bag, but easier to work with, and less expensive than the sturdy nylon I planned to use for the final bag.
I used paracord to make the drawstring and fed it through the hem using a big safety pin. I had a few of these spring-loaded closures hanging around, called cord locks, and so I used them for the drawstring adjuster. This particular size is a pain to get two sections of normal-size paracord through it, but by the end of this project, I developed a technique that works reliably well.
I used a piece of cardboard to stiffen the bottom of the bot compartment and folded the tabs under it to attempt to make a bot support bracket. I didn’t think the cardboard one would hold up, but I wanted to test out the geometry of everything.
Of course, it got smushed the instant Jayy tried this one on with any weight up top. After completing the first test fit, we decided the bot needed to sit further forward on the shoulder than in this initial design, so I needed to make the bot compartment its own separate piece.
Adjusting the Design
I 3D modeled a platform for the bot to sit on, to be affixed to with zip ties, using PETG filament, which is less brittle than PLA.
The fabric top of the robot compartment remains the same as before, but I needed to do its machine stitching before attaching it to the rigid base.
This drawstring cord lock still gave me a lot of trouble this time, but I promise I’m getting closer to the ultimate tip for this situation.
Then I sewed the drawstring bag to the 3D printed base around the edge by hand. Since I wasn’t sure where exactly the robot’s waist was, and wanted it to be flexible for future robot versions, I added some nylon straps for cinching down any extra fabric.
The rest of the bag came together similarly to the first prototype– I made the strap with a sandwich of nylon and upholstery foam, two layers this time, and used 1-inch webbing for the straps, with compatible 1-inch buckles and D-rings and all that. The thing that’s new in this version is the use of grommets, which I’m using to make the link between the platform and the strap, as well as for the backpack compartment closure.
The idea to make the platform perforated for attaching the robot was the real breakthrough in the stability of this design. Jay reports that this backpack holds up his robot companion securely and comfortably.
So I made a second basket assembly with rounder 3D printed edges, since it’s easy to swap the whole basket out on the backpack base. I used orange canvas for this one, and hand sewed the fabric to the base. The base is held to the strap with two more pieces of paracord.
And finally, here’s my tip for getting the two ends of the paracord through the cord lock device– you can tightly wrap the cords together with thread, then push them through together. It’s the same sort of technique some folks use to remove a ring that’s stuck on a swollen finger. Or, you can just buy bigger cord locks… But I was determined to use the ones I already had.
This was such a fun collaboration and a really satisfying design challenge. I love working with my friends, Jayy is just the best, and the result is better than either of us imagined.