I prefer not to think about what goes on up there. I remember when I was instructing, we got told by someone in the know that on an R22, at flight RPM (104%) there was 4t of force on the attachment bolts, overspeed to 110% and it went up to 9t. They also said that if it got to 117%, the tail world come off. Kind of focuses the mind.
The rigid head actually was trialed on the Gazelle. It was taken up on the 105 and continued on the BK117 and EC145. It's good but it shakes your teeth out of your jaw. Those baubles you see are the pendulous dampers. Supposed to take some of the vibration out of the head.
Depends on how the head is constructed. The fully articulated head on the 500 is simple because it uses a strap pack instead of hinges. The 300 however has lots and lots of moving parts... Smoothest helicopter I've flown?? Uhhh I guess Reid's Squirrel ZK-HEX is or should I say was, the smoothest. The 105 I'm flying now is pretty good, still rattles through translation but in the cruise it's nice.
I love helis though I have only flown in one 8-10 times and been at the controls for maybe 40 mins. I did once read a book called "Fatal Traps for Helicopter Pilots (or something like that) - there is certainly a lot to think about !
-- Jeff, Rolleston, NZ P3Dv4.x and a bunch of add-on stuff... some 'global' products, but otherwise NZ-only