Dan:
I'll jump in here. William Robinson is exactly right Look at the diameter of an auto-gyro. It's effectively the wing of the aircraft. It produces lift with the drag being used to effectively turn it. If you have all three props on the same axis, the powered prop in the center will produce thrust while the outer free rotating props will only produce drag. Effectively they will act as brakes. There is no auto-gyroscopic effect.

John