To all of us Nerds
,
I think the Cheyenne gyro was actually intended as a true gyro, that is certainly how it is described in one of Prouty's books, added to modify the rotor response and stability. It was a heavy ring , first mounted below the rotor but later moved to above it. As Lu said, it was an ongoing project, many major mods were carried out as it ran (stumbled?) along, before being cancelled for a number of reasons.
We should all realise that, as indicated by the Lockheed designers having all these problems, we really are talking about a complex issue here!
Dave,
One thing that occurred to me earlier is that a "rigid" rotor is not actually completely rigid in the literal sense so perhaps we have all been slightly barking up the wrong tree. The term "rigid rotor" actually means that there are no flapping or lead /lag hinges but there is an inherent flexibility in the system, either within the blades themselves or on the rotor head, like on the Lynx.
Juan de la Cierva did originally attempt to fly an autogyro with a truly rigid rotor by fitting bracing wires between rotor head and the blades. He did this because when he scaled up to full size from a model he was alarmed how much the blades drooped at rest. It rolled over on takeoff. He later realised that his models' blades had inherent flexibility, allowing them to flap to equality. Bracing up the full-size blades caused aerodynamic loads to be fed back into the fuselage, giving a massive rolling force that the pilot could not overcome.
Lu, please note, that accident was put down to inflow roll, an aerodynamic, rather than gyroscopic phenomenon.
ShyT