delta3,
I agree. The side hinges are intended as coning hinges. These hinges were probably included to minimize out-of-plane bending moments in the roots of the blades and grips. This probably allowed for a lighter rotor.
Some thoughts.
" - as the blades cone progressively the pen will show the increase from rest to max coning"
My previous posting was not clear enough. Both bolts rotate with their blades, therefore the cardboard and the pen will rotate. It would therefore be possible to see if the rotations were synchronized or out of sinc.
" - if they would flap then they have to go negative,"
Not necessarily. This is a low inertia rotor, therefore under heaving loading the rotor will have a reasonable cone.
" - No unreasonable frictions (bolts stuck or so)"
All three R-22 hinges have a resistance to sliding friction of up to 22 ft-lb., under no load, when initially installed. The bearings appear to be of the sliding bushing type, therefor the breakaway friction will be somewhat higher. [Lu ~ for an unrelated reason, would you confirm that these bearings are actually bushings and not needle bearings. Thanks] . Granted that the static friction under load is very small when compared to the centrifugal force, but under small angle consideration, they will be quite close.
IMHO the concern, if there is one, would be that during an abnormal aerodynamic moment and/or control input the flexible blades may cause the rotor assemble to actually 'flap'. This combined with the delta3 MIGHT prove interesting.
Dave