Nick,
Thanks for the affirmation - that exactly what I thought!
CRAN
Sprocket,
The EC120 certainly does have and elastomeric rotor head. It uses LORD spheriflex bearings - as do many modern hubs. The spheriflex bearings don't necessarily increase the control loads substaintially, there purpose is to do the same thing as your flapping, lagging and pitching bearing sets but by eleastic deformation of a single bearing/flexture rather than 3 sets of rolling surface bearings.
They are really neat little things!
Essentially spheriflex bearings are hemispheres made up from laminiates of exquiste hybrid rubber-type materials and high grade metallic materials. The reason why we use them instead of discrete rolling element bearings is principally the reduction in maintenance - no lubrication and massive reduction in hub complexity.
Elastomeric articulated hubs are typically significantly smaller than an articulated hub with 'normal' bearings and also require less maintenance, can be cheaper, lighter, and can be less draggy (by virtue lower area and simpler geometry)
As Nick explained above the main source of control loads in helicopters (with modern aerofoils) is the aerodynamic pitching moments created about the chordwise attachment position, not the nature of the bearings used to accomadate rotor motion.
Though for clarity I guess I should state that because elastomeric bearings require the 'torsional deformation' of a material then of course the material will resist this hence creating a small additional control force that the pilot/hydraulics must over come (in pitch) whenever the bearing is not in its neutral position.
Hope that helps
(I'm sure Nick can add something of value here as the S-92 uses some very nice Elastomeric bearing - and BIG ones too! - Saw them at Farnbourough)
Cheers
CRAN