At this time, I am stuck on finding a suitable gearbox for my model. Two types were used with one from a Honda motorcycle and one purchased from a local distributer. I haven't had much success in determining the "gear box drag" and it's effect on the autorotation of the blades. The blades won't spin-up in front of my floor fans when rotors are coupled to each other's gearbox. They spin-up OK when not coupled.I understand that mate, Just wondering how it all worked out?