GR-3A - No horizontal Stabilizer - Offset Gimbal hinge - Micro Autogyro
344 views · Published 21 July 2017 · 2:57 · Indexed 29 October 2026
Channel: RCmags · 2017 · Entertainment
This model autogyro is a concept demonstrator. Unlike my previous models, this aircraft does not use a horizontal stabilizer to achieve both static and dynamic pitch stability. In this case, the model obtains static stability by using an offset gimbal hinge. This consists of placing the rotational axis of the control gimbal on a fulcrum, and this fulcrum is then attached to a stiff spring. As a consequence of this mechanism, when the rotor sees an increase in loading, the spring is expanded and the rotor is tilted downwards. This has the effect of providing nose down cyclic. As such, lift increase are coupled to a nose down torque and static stability is achieved. For pitch damping, this offset gimbal mechanism will not suffice. The rotor must somehow provide this source of stability. TO do so, the rotor blades were made sufficiently heavy as to induce this necessary damping. With a horizontal stabilizer, this effect is achieved without the need for larger blade mass. The combination of an offset gimbal hinge along with heavier blades created an aircraft that seemlingly did not diverge in it's pitch trajectory. That is to say, when disturbed either by pilot input, or by a gust of wind, the aircraft did not begin to accelerate about the pitch axis. Likewise, the stability seemed to remain unaffected at high speeds. The closest analog to a fixed wing aircraft, as compared to this autogyro, would be a paraglider. This type of aircraft is solely stabilized in pitch by a low center of mass.
