Matty
Actually the Hitachi with what looks like a "full centre post agitator" isn't at all, it is a pulsator with a post in the centre. These were "invented" by Hitachi and were advertised as a "pul-gitator". They work like a pulsator in that they have very fine fins and move fairly fast, but the centre post was added to reduce tangling. They turn somewhat slower than the older small diameter pulsators as a small reduction gear is fitted below the tub. On the Hitachis it is a 4:1 reduction so if the machine spins at 800 rpm then the pul-gitator turns at 200 rpm. They reverse more often than the older design too, they reverse about once every second or so, on gentle they turn then pause, then reverse then pause. They wash MUCH better than the older impeller types and were very popular. The GE 600N with pulgitator (by Hitachi) was tremendously sucessful, prompting Hoover to release the Premier which washed even better but the reliability was pretty terrible, and Simpson released the Genesis which was not as good a washer but very successful anyway. All Australian made top loaders now in production (except FP)are derived from these clones of the original Hitachi product though they have evolved over the years.
By way of clarification - true agitator action machines have a transmission which does the reversing, the motor continues turning in one direction for the wash cycle. They tend to rotate about half to three quarters of a turn with each stroke.
Pulgitator washers have a simple reduction gear instead of a full transmission, the motor stops and reverses for each stroke of the pulgitator. Generally this allows the agitator to complete about one full revoluton, sometimes up to two revolutions at each stroke, which gives them their excellent wash action. The GE badged ones were labelled "agitator action" for a while but they weren't. Simpson did it too, when their true agitator action machines were discontinued and replaced with Australian made Hitachi copies, they were labelled "true agitator action" too, even though they weren't either. The term "pulgitator" was introduced by Hitachi but never caught on and are called agitators now, though I think it is a useful distinction to preserve.
The Hoover Premier had a 7:1 reduction gear, this gave the (small) motor tremendous leverage over the agitator, allowing it to use a large diameter agitator which was almost the full base of the basket, and it turned about 1.5 to 2 revolutions at each stroke, giving it a really great wash action which earned it high scores in Choice mag, but the reduction gears were plastic and couldn't take overloading, plus quality of the machine was pretty crap overall. These machines were introduced when Maytag had bought Hoover Aust, and were trying to downgrade the Hoover name to be a cheapy product, introducing Maytag and Admiral branded machines as their premium products. Before then Maytags were only sold in Au for commercial use.
Anyway I am raving on again...
Chris.