WaterWar.net

If it was smaller and lighter, would these work as a crank pump??

http://en.wikipedia.org/wiki/Archimedes_screw

I guess it could be made to work, though I don't really see any advantages over the traditional pump.

Less force. Also, If you were to use it via stream/river, it could be a stream QFD. I don't know yet.

While good for lifting water up slopes, since the screw is, in a sense, an open channel, if you try pressurizing a PC with is, you'll eventually end up just pushing water back down through the screw towards the lower-pressure reservoir. I don't believe one can really get that sort of system to build up the pressure needed to create a good stream.

Took the words out of my mouth. Gravity just won't make enough pressure, I'm afraid.