Mechta,
From my simple "agricultural" eye of engineering , when we ( my mechanics and I ) started to dismantle the front end(prop end) of the Griffon 58 we removed all the streamlining then started on the hydraulic feathering pot , this in turn was connected to the front prop, which was connected to the two way thrust bearing(this had a rotary oil tank and I cannot remember its name) this in turn was connected to the rear prop, all these Prop to bearing connections were highly engineered straight bars with gear teeth cut into the diameter of the pull/push bars, when any command from the cockpit to alter the pitch of the props was made the props worked in unison, it seems it was unable to offer alternate pitch degrees to the twin set of blades, unless some initial offset was put in at the final assembly of the prop sets. the hydraulic was fed by an internal oil tube coming from the front of the gear casing thru the center of the prop shaft set, and the rotary oil tank pitch change bearing it seemed had a service life of 100hours but all the record cards I ever saw suggested that these were changed almost weekly, when the Shacks were in service, it was the failure of these parts that caused the loss of Pelican 16 into the Southern Sahara desert whilst it was on its way to the UK for a refurb
Perhaps a more enlightened aero engineer could make my explanation easier to grasp!
Peter R-B