Everything in this entry comes straight out of the teardown work: real failure points found in real original cartridges, and what they mean for the reengineered version. The goal across all of it is the same: complete serviceability, real durability, and an archival intent, built to last at least fifty years, with no reason it couldn’t go longer.
The original shell is injection-molded ABS, glued or solvent-welded shut, which means it’s genuinely impossible to open without destroying it. That single decision is behind most of what follows: nothing inside was ever meant to be serviced, because nothing was ever meant to be opened.
The main drive gear is the clearest example. It’s thin, likely polyethylene (possibly POM, hard to say for certain after decades of wear), riding on a shaft only 4.5mm across with a 3.3mm square drive. That’s a genuinely fragile part carrying real load, and it’s heat-staked onto its shaft, so there’s no way to replace it short of destroying the assembly around it. It was built disposable, whether or not that was the intent.
Inside, the lever arms that apply tension to snap film through the gate, and several of the roller wheels, appear to be the same degraded polyethylene. A lot of the lever arms we’ve opened have simply broken off. Whether that’s ordinary age, heat exposure, or just decades in unknown storage conditions is impossible to say in hindsight, which is itself part of the lesson: whatever we use next needs real heat resistance built in, not assumed.
Even the optical side has a failure mode: the mirror element is just a piece of Mylar, glued in, and it comes loose often enough that it’s clearly a weak point rather than an exception. It’s a small part, but it sits directly in the sightline, so it doesn’t get to be an afterthought in the redesign.