Rotorheads

HIROBO Rotor Heads

Original Rotor head (1976)

Original rotor head as fitted to 77 Falcon.

Hirobo's original rotor head incorporated collective pitch as standard but was of an 'old' design that had been tried, and discarded many years earlier by European manufacturers. This design was such that as the swashplate moved up or down to impart collective movement to the main blades it also resulted in a 'pitch' change to the flybar paddles. This head was very stable but the movement of the flybar paddles made it very inefficient outside of a small range of setting around the Zero flybar paddle position. Pilots generally set this position to suit their flying style; for beginners it would have been at the 'hover' position so as to give good control whilst learning; for more advanced pilots it was changed to give zero paddle setting at the 'circuit' position so as to give good flight performance.

Collective De-coupler Rotor head (1977)

Original rotor head upgraded with de-coupler.

To remove the inefficiency of the original head due to pitch movement of the flybar paddles, a 'collective de-coupler' was fitted (also available as an upgrade) to ensure the flybar paddles stayed 'fixed' resulting in more positive cyclic control. this was an arm that 'arched' over the head and effectively 'locked' the separate flybar paddles together ensuring that they operate in the same plane. below the 'weighted' top pieced was a vertical shaft with a sliding collar connected to the original flybar control links. Thus as the swashplate moved for collective pitch control the collar would slide up and down without affecting the paddles. However, when the swashplate moved with a cyclic input it would rotate the collar and impart the movement to the paddles. Unfortunately due to the geometry of the layout when increasing collective pitch, cyclic control would reduce due to the increased distance of the pivot point above the flybar itself which then reduced the amount of flybar rotation. Not really an effective cure and was a development 'dead end' so the use of the de-coupler was discarded.

Scale rotor head (1977)

scale rotor head close up and exploded views.

A number of weaknesses had been identified in the original (and de-coupled) rotor head and swashplate control system so it was completely revised and now incorporated a 'see-saw' assembly above the swash plate such that when the swashplate moved vertically (as in pitch changes) the flybar rod did not move but, if the swashplate 'tilted' the flybar rod followed this movement. It was also decided to model the new rotor head on the 'full size' Bell Huey helicopter as this was the machine the head would initially be used for and thus significantly increase the models scale fidelity.

Two blade rotor heads (post early 80's)

DDF - Head

Shuttle-Heads