If I weren't so busy I'd have had lots of opportunities to submit to the Hackaday Fail of the Week tip line.
Learning experiences documented here to help others not make the same mistakes.
- Steering Mechanism: The original screw based design was too slow. I then moved to a cantilevered design with a pivot arm to multiply the force given by a stepper motor. This worked very well, except that the stroller's frame was simply too narrow to allow a reasonable turning radius. My calculations didn't account for the additional dimension of the pulley on one side. It contacted the frame meaning we could only really turn in one direction. The fixed wheel stroller is still so much more stable than the pinned swivel wheel; the fixed wheel stroller it's 100% usable without a steering mechanism.
- CCD Lens: I have a linear CCD soldered up, a steering algorithm in my head, and no way to test it because I can't find an appropriate lens. I made a few trips to Goodwill, but of the cameras I found there were either wild focal lengths or ended up having tightly integrated lenses. I'll probably need to source this from oversees but unfortunately with the lead time it seemed prudent to work on other parts of the project. When I find a source I'll post it in the components section.
- Battery Exploding: Well, not exploding, but the hiss of a large expensive charging lithium ion pack is enough to impress the importance of battery safety on me. I mustered the bravery (?) to grab it and get it outside in case it did flame up, but in the end only a few cells were damaged. The culprit? Bad spot welds from my initial hack of a spot welder came free and focused charging current through the few cells in a parallel bank that were still attached. This necessitated waiting for more cells to arrive, rewinding the transformer with heavier wire and fewer turns, then controlling the weld attributes more tightly (at all). This week I plan to disassemble the entire battery and rebuild it properly, placing the cells in a 3D printed carrier for rigidity. I feel silly for relying on hot glue at this point.
To be blunt, there's been a rough patch. But every time I go out to run with the stroller I'm convinced that it's a worthwhile project that will have a lasting impact on my health (and quality of life) decades out. So we just repeat the process: identify problem, identify (new) solution, implement it!