If you want good mechanical insight there are several A&P and IA's at
the Yahoo group entitled:
robinsonr22helicopters
The above is the exact spelling. Just go to yahoo and then "groups"
then search for it.
Very good forum. Not all the experimental/hybrid/never-get-off-ground
junk like here.
Also, try PPrune.org
Another excellent heli site.

Good luck!