Thanks for posting that. Very interesting. I guess we could call that a "three-tub," abbreviated 3T.
SactoTeddyBear, I'd be interested in finding out more about the one you know is still in service. Specifically, manufacturer and model number, and where the manufacturer is located. And if they ever plan to scrap it out, well, I live in the Bay Area, so...
This also gives me an idea for a way to improvise something like this. The simple version is two wringer Maytags or equivalent, with an extractor between them. (One wouldn't necessarily use the wringers on the Maytags, just the washtubs) Though I don't know if it would offer significant operating efficiencies over a twin tub for residential use.
The key to energy efficiency has a lot to do with the choice of motors, and getting the best results from a given motor depends on the design of the other components, i.e. washtub and agitator. This in turn gets us to another interesting question. Assume a top-loading washtub with American-style agitator. Conventionally the washtubs are cylindrical. But we see on POD here, a lot of unorthodox washtub designs, for example semi-spherical.
The washing action in an agitator-type TL is basically a toroidal flow. But a toroid does not intersect a cylinder particularly well, i.e. there are dead spots in the "corners" of the cylinder. So now, how'bout designing the washtub with a "bulge" in the center of what would otherwise be a cylinder, and a wider-radius curve at the bottom...? I can picture this in my mind's eye, and it seems that it would do a better job at capturing the kinetic energy of the toroidal flow. The shape of the agitator would also match to the inside curve of the toroid, and have fins designed to maximize the water flow at the bottom circumference.
Hmm, anyone have any feedback on this? Does the toroid-shaped washtub idea sound workable, or does it sound like someone spiked my pipe tobacco with that funny green stuff..?