Hi greg.  I tried that whirly exhaust fan years ago -got the biggest one  from the manufacturer -damaged,for free. I sat it up around 40 feet with a small belt drive(printer ) and a small pm 12 v motor.

In a stiff breeze it barely moved and as soon as I shorted the leads it came to a sudden stop -- So, sorry,but they won't work.

If you are up Mt.tamborine way one day ,call in and I'd be happy to show you a few things .

brucedownunder@hibis.wbs.net.au

Cheers,bruce