Here are my speculations....
- Introduction of electric motor operation as opposed to manual operation
- Electric motor driven Pump technology. (As opposed to gravity drain)
- Agitator technology. (Going from cups which move up and down to agitators)
- Agitator design. (Ramped vs vaned agitators)
- Wash timers which shut the machine off when the timer finishes
- Multi-speed operation. (I've never seen more than 2 speeds so far)
- Recirculating lint filters
- Draining design. ie. Sloped tub on the bottom for easy cleaning
- Safety bar for the mangle, in the event a limb gets caught in it
- Bi-Directional operation for the mangle.
- Double tub construction. (Speed Queens were well known for this!)
I kind of figure that technology advancements in the field of wringer washers pretty much stopped sometime in the 1930's prior to WW2. When Bendix introduced
their automatic washer in 1937, it was pretty much game over.
Mind you, I'm sure there were some minor styling changes in the 1940's after WW2, but after that, a Maytag wringer built in 1946 closely resembles one of the last ones they built in 1983, without much in the way of changes.