OK Dave, Lu - I finally figured it out! Cool stuff, but...
Dave (or anyone), coupla Q's. It seems to me that only four blades will work on this hub (or two, but then what's the point of the double U-joint). For instance, if you have three blades, then when the blade at 90 deg was flapping up, both the other blades (at 210 and 330) would have to flap down - what am I missing?
Four would work because cyclic feathering would hold the blade angles constant on the 0 deg and 180 deg blades while the 90 and 270 blades were flapping (and so on).
I take it would you would rely on hefty, broad elastomeric bushings and wide contact areas to provide the couple between rotor hub and mast (to give that articulated/rigid airframe/control response).
What I wonder is given the number of bearings and pivot points, and the way the torque has to be transmitted, are you really going to gain much in simplicity, maintenance or weight savings vs a "traditional" fully-articulated rotorhub?
Just so you know, I just spent the last hour buinding a model of your d***d rotorhub out of an old yoghurt container and some Q-tips...
Hm, 'nother question. if you have the blades underslung in relation to the virtual pivot point, then when the 90 - 27 blades are flapping up and down, won't the 0 - 180 blades be traveling in an arc when view from directly behind the disk?
Not sure how to describe this - imagine you were standing nose-on with the blades perfectly aft-forward/side-side and someone pushed the right-side blade up. The blade-tip you were looking at would scribe an upward arc to the right. Am I making sense?
