Lu,
I love your conviction and belief that all you hear is true.
"To my understanding Frank Robinson designed his rotorhead and then designed the helicopter around it."
As a pilot, which you reportedly are not, I cannot believe that, if the 18 degree offset was a cock up, that the R22 ended up such a good machine to fly. Make no mistake, Frank Robinson is no idiot. 18 degrees was planned. The story that got out is the one he wanted to prevail. It may not be true but the result is as desired. His design prevailed. If, as you suggest, the rotorhead was designed first then it is a tribute to engineering genius that it flies as well as it does. I suggest this is not the scenario as I do not consider Frank Robinson a genius either. His ramblings on this very matter confirm this. For a start, if he was so good, why muck up the head in the first place.? Why not do the conventional, easy thing and go for 90 degrees phase lag. Cone hinges could be designed with 90 degree pitch horns. We are not privileged to access the true development of the R22, nor the failures along the way, nor the reasoning behind the unusual features. The R22 is not an accident. It may not be the result of conventional engineering but maybe that is it's success. I suspect without the 18 degree offset, however Frank arrived at that figure, the R22 would have been less good than it is.
72 degrees phase ange is crap. 90 degrees is not negotiable. Why on earth should the incorporation of cone hinges and 72 degree pitch horns determine the phase lag. This could be allowed for in the design of the rest of the control system, notably the effect the controls have on the swashplate. Frank could have selected any phase offset he liked without altering the rotor head.
I am not saying you are wrong, in fact I think you may be right(!) -and the phenomenon you have described is to the benefit rather than the detriment of the R22.
I'd still rather have my Enstrom!
