ok so some feedback on this

Got the alternator wired up as per the diagram (thanks DD) and after getting some volts into the target battery (via regular battery charger), it all work a treat!

Charge light comes on, when hooked to a battery, but not running. As soon as I start the motor, the charge light goes out and the alternator is charging away.

But... (there is always a but)

It seems that the alternators internal regulator is shot. Voltmeter shows 17-18 volts going into the battery. Bugger. So Im looking for another internal reg alternator for this setup. About 35-50 amps is what I want.

And, it seems that 1/4hp electric motor isnt enough. After running the setup for about 15 mins, the old motor (that i fished out of an old spares bin) got far too hot and started to struggle. So i also need a more powerful electric motor. Bugger.

So, all in all, the concept works as designed, and for zero cost. So I think I have achieved my goal here. its justa pity that I need to find another internal reg alternator and a bigger electric motor. by the time I purchase those two items its getting to be an expensive project.

I've got a 120 amp Prado alternator sitting here in the shed (brand new!) that i could use,(but thats such a waste and overkill) but i still need a new motor.

Anyone in Perth want to donate to the cause?