Hey hey, this thread is getting pretty interesting...
"Envision the two counter-rotating gyros replacing the gimbaled gyro and I see no reason why this gimbal activity is not applicable to the two counter-rotating gyros."
Well ok using your CVJ+HS hub system, the compliance will allow some seperate gimballing. Hence there will be an initial increase in apparent rotational inertia in pitch or roll, until the hub spring reached equilibrium. Not sure whether the spring limited compliance would really damp the pitch/roll or just limit inertia increase to an initial resistance. For the sort of pitch/roll damping you are talking about you would normally design a damper into the gimble (ie torque/rot_velocity), so that gyro only providided part of restorative force required to resist input.
Don't forget this is all at the cost of reduced clearance between contra-rotating rotors, hence risking rotor clash - pilots are (rightly so) a hard bunch to convince about the safety of a machine. You really do need to build a test rig to understand this interaction properly, before moving on. At any rate this all provides resistance to gust loading, but does not adress my primary concern about pilot controlability - ideally cyclic position would directly control pitch/roll rate.
"If someone knows how to build a successful rotor that is incredibly rigid ... he is hiding that secret from the rest of the planet."
Agreed, and is why i suggest either coriolis correction or damped lead/lag movement. Prouty makes the point very strongly that even a "rigid" blade can be given an effective offset hinge dimension. Dave's proposed CVJ+HS is a half way house design, which aims to keep hub rigidity below rotor without altering pitch horn lead angle. I don't suppose the design will stop with that, but it is a good start - certainly until the dynamics are understood better.
"How about building the thing, already?"
Must admit some practical ground test rigs would be nice. As an engineer i appreciate how much time (and money) this sort of engineering endeavour costs, this is why i have offered any cad/FEA help i can. It is all too easy to start on the wrong path, and run out of cash...
Lu, thanks for the fascinating insight into the Cheyenne system - i have been an admirer for some time. You would be suprised how much of a headache the hydraulics can cause on even a prototype articulated mining truck! Would you say that the Lynx system is the way to go for a private helicopter? I have been thinking along the lines of cost and reliability, hence the idea of a fully mechanical system over an electronically controlled servo-hydraulic system - the CL475 (once the three bladed rotor was fitted) seemed to prove this point. Westland are considering elec-servo to replace the hydraulics, which is a good route but one that must be safety proven (as it has already been in fixed wing) - I would be concerned about development costs.
"The springs would return to their static position ... This is similar to the control input to that of a fixed wing aircraft."
This is very much my reasoning behind incorperating it into the Unicopter development program. Must admit i still find flying the R22 in a turn an interesting experience compared to (say) a K8 glider - admitedly my pedal reflexes are still a little incorrect. I think a complete avinitio would really struggle though.
Dave, I appreciate that the full helicopter design is still to soon. I have admired your packaging bucks, and would like to suggest that maybe it is time for a dynamic test rig. I'm not proposing anything too fancy, but it strikes me that there is a lot of debate speculating about the interaction of the twin rotor hubs, the fuselage, and the control system. Even a simple gyro mass test bed is a good start, and would allow a natual progression to the blade development. Do you prefer to discuss technical issues in detail on this forum, or is there another venue? I'm keen not to outstay my welcome on this forum...
Is there a development grant in Canada that would help you get started? I think you could put forward a good case.
Mart
Last edited by Graviman; 30th Apr 2005 at 17:14.