Having reassembled the Auto-Mini as a project for keith, I took it for a test ride today and was reminded of my one complaint about the machine: it managed to feel simultaneously overgeared and undergeared at various times. I assumed this was the miracle of being a heavy, clunky folding bike.
But today, I was giving it one last ride for fun, and I took a closer look at the rear hub. It's a Sachs Torpedo Duomatic. Eh? With a name like that, it has to be a multi-speed hub, right? But I had always discounted that idea because there was no shifting mechanism. But today I took a closer look, and watched the holes in the sprocket to see if they stayed aligned with the oil fitting on the hub. No! That meant it had to have internal gearing, for nerdy bike reasons.
Google to the rescue. It's a "kickback" hub. The shifting mechanism is a light backpedal, which pops it from one gear to the other. Remarkable, and suddenly much more functional. An exploded view.
It still doesn't fold very well, but at least it has two speeds.