hi sundowner the 450 grm refers to weight of the matting in sq mtrs, its a standard used through out industry, you get all grades and its sold by its "weight per sq metre" just nice to see ya taking notice ....lol. donnie.
I've also built another small turbine from a DC motor I imported from the States. It's currently being tested in my back garden (bench tested at 9 amps ish). I'm open to offers if anyone is interested but if not I'll be sticking it on ebay in a week or two.