Thanks Nick. A brief google search revealed:
Blackhawk:
http://www.b-domke.de/AviationImages...hawk/3416.html
S76:
http://www.kiwiaircraftimages.com/pages/s76a6.html
and a very neat S76 RC model
:
http://www.v-eastonline.com/SikorskyS76.htm
So basically the compliance in the spar root behaves as if it was an elastomeric bearing. Very simple, and very reliable i imagine. Although these are all power augmented, i would imagine that a non power augmented heli would suffer high control forces.
What looked to me like hydraulic ram fittings in the hub must have been a red herring, or part of the pitch control mech.
Mart