To: Try Cyclic.
In reading the entire article, it is a mixture of descriptions of real rotor heads and model rotor heads. In the descriptions of real rotorheads I could find no fault nor,could I find fault in the description of the model heads. However in the model heads section they were talking about models with fly-bars which the Robinson helicopters don't have. It appears that the description of the swashplate off-set was to compensate for the problems of the fly-bar and other mechanical problems in the control system.
I have seen model helicopters fly but I have never really examined the control systems or the rotor heads. The author addresses flapping and leading and lagging. What he says applies to a real rotorhead with offset hinges (Fully articulated) but not having a detailed understanding of model helicopters I don't know if they have fully articulated rotorheads. While working in Germany I saw a beautiful model of a BK-105 that had a rigid rotorhead but to my knowledge all others have fly-bar rotorheads. If wrong I will stand corrected.
Additional Info:
When you have an offset hinge on a rotorhead the swash plate is offset by 45 degrees and the pitch horn leads the blades by 45 degrees which gives a total of 90 degrees. In this case, the swash plate tilts 45 degrees prior to the direction you wish to fly. The advancing blade is 45 degrees ahead of that position and therefore, it has its' lowest point of pitch. Conversely, the retreating blade has its' highest point of pitch and with 90 degrees of precession the disc tips down over the nose and, up over the tail. It has to add up to 90 degrees.
The Robinson rotorhead because of its' design has the pitch horns leading the blade by appproximately 72 degrees and as such the attachment points on the swashplate are positioned under the pitch horns. The swash plate however tips just like a Bell swashplate. So, the lowest point on the swashplate on a Robinson is over the centerline of the aircraft but, the blade pitch horn lags that point by approximately 18 degrees which means that the blade must travel an additional 18 degrees before it reaches the point of maximum down pitch and the same is true for the retreating blade. This means that the disc will tilt down 18 degrees after passing the longitudinal centerline and the helicopter flys left unless the pilot compensates for the 18 degree difference.
Look at this website:
http://205467.homestead.com/diagrams.html
[This message has been edited by Lu Zuckerman (edited 20 November 2000).]
[This message has been edited by Lu Zuckerman (edited 20 November 2000).]