This model contains some ideas about creating fully articulated 3-blade Bell-type main rotor in Technic in 1:20 scale.
Creating fully articulated rotor requires flapping hinges and yaw hinges/dampers besides pitchable blades. In more modern rotors, flapping and yaw hinges are replaced with torque tube and elastomer joint of blade allowing flapping/yaw movement. In Technic, building pitchable blade with flapping and yaw hinges would result in a very bulky and complicated rotor, not suitable for Lego tech figure-scaled models (1:18..1:20). Torque tube with elastic part inside it is even more troubleful.
However, if we combine parts "3 stud hub" and "rubber tie" parts carefully, we can create reasonably small articulated rotor. Blades have spar-and-ribs construction and covered by decals. Blade spars are connected to upper arms fixed to hub through rubber tie: it allows flapping/yaw movement of the blade, and also alows pitching it. In pitching the blade, rubber tie acts as a torsion spring, gently forcing blade to zero pitch. Blade pitch arm and pushrod can slide in a 6-hole driving plate placed beneath of rotor hub, and can pitch blade against the force of torsion spring. This way, swashplate can be just a flat, tiltable and liftable plate with a hole in the middle letting through main rotor mast.