RE: Rotor Hub Dimensions
John
Yes I did use poly for the roll hinge. I think the diameter of the kellerva rotor was about 42". I used Futaba s148 servos. Thats the biggest gyro I have ever built so I don't really know if a 3004 will do it......give it a try!
Kellerva was just a little experiment and seemed to fly ok. The double control rods were used because 1 tended to flex too much when pushing.
Sean