Hi, can any one tell me more about which type of turbine (pelton, francis etc.) would be most effective when reduced in size-(as small as 15-25mm Dia...), when high speed is required. Are there any companies out there that manufacture small impellors or turbines that I could buy off the shelve? Or can someone supply me with technical information or formula to design such a turbine. Do you think a pnumatic tool (air driven turbine) will be any good in water?