Please somebody explain to me what's the net possitive effect for the flow of solids between rotating the casing vs. spinning the shaft? I can see the merit at filling point as material is driven from the outside in and certainly with no void volume although this can also be achieved by standard designs with flight and pitch sizing. Another positive could be the length that can be built as would suffer less bending and torsional load BUT mechanically rotating the body adds extra complexity at the motor as gears and air-locks would be needed. <br>People clearly has thought about this before, but a screw feeder is a cheap and cheerful piece of equipment, and it does the job: why reinventing the wheel?