Interesting. Never knew the spin speed on a DD before; I wonder if the full-sized versions spun at 640 as well.
The early WP/KM BD portables (late 60's??) were 24" full-sized machines in a portable cabinet, with a single-inlet water valve (no temperature control) and retractible wheels. They had a large 12 lb. tub, and spun at 525. Not sure what the speed was on the later, smaller models, but I know it was fast. The earlier version seemed more practical; not sure why Sears/Whirlpool discontinued it. I've seen the "small" BD portables and the tubs appeared quite dinky. Same with the DD models and ThinTwins. One of our members has a full-sized Kenmore portable, but I don't remember who.
As a sidenote, I was looking at the underside of my GE (Hitachi) portable and, aside from a larger pulley that drives the impeller connected to a smaller motor pulley, there was virtually no reduction gearing for the tub. A monster solenoid energizes, pulls out the clutch arm, and off it goes, spinning at the same speed as the impeller during the wash cycle! No wonder it made a "Wa-wa-wa-wa-wa-wa-wa-wa-wa-wa" sound as the motor picked up speed!
