To: Nickii,
Thanks for the NASA site, it does indeed answer some Q's but not I think, as clearly cut and dried as some people may think.
Some Q's for you if you don't mind...
1. Is the theory you have described:
"The N per rev vibration is a natural effect of the blade's motion around the head, and is intrinsic, as is the 1 per rev resonance of the blade in flapping. The rotor delivers a "root shear" to the head that sums at the head to the n per rev vibration in the static system.",
that of Sikorsky's (I assume Jerry Abbey's) or your own??
2. Can you elaborate further your explaination of a 1 per being a function of the blade flapping?? I was always under the impression that a 1 per was a function of an out-of-blance condition.
3. By "root Shear" (luv that term), I assume you mean a transmission of energy from the blade to the mast (via the root obviously)???
4. Is this "shearing" a vertical or a lateral vibration??
5. In your experience (or Sikorskys view) what flight regime are n pers most noticeable???
6. In your ref:
"In the rotating system, this vibration has two components, at N+1 and N-1 per rev. In other words, an absorber attached to a 4 bladed rotor head will see 3 per rev and 5 per rev vibrations, and the transmission will see the sum of these two as a 4 per rev."
7. Finally, what CAUSES the vertical component and lateral component of the N per rev vibe (not N+1, N-1 vibe)??
Are you referring to the Bifilar as the absorber of in-plane N+1 & N-1 per rev vibes - I assume so - not the n per rev absorbers typically fitted to the airframe??
For Wunper,
I agree with your observations, but now some Q's if you don't mind,
1. At what flight regime/s do you smooth the n pers in the Lynx??
2. Therefore, at what flight regime are N pers most noticeable i.e. when are your aiframe absorbers working the most??
All for now....more to follow ....over.
Bulls**t Baffles brains