Tail rotor "pitch slop"

[soarin77]

For anyone who knows the Bergen gasser EB pretty well;

After hours of narrowing down the possible problems with tremendous vibrations, I think I have come to a conclusion. Now the only problem is figuring out how to correct it.

Long story short, I have had some problems with hardware stripping, shearing, and rotating loose on the aft end of the bird :arggg:. I just noticed today that the tail blades (during rotation) seem to have play in them. The blades are tracking fine and are even balanced pretty well. Its almost as if I am giving minute/small movements to the tail. Very rapid and incredibly small.

It seems that the ball joint on the swash unit does not fit snuggly into the ball socket in the tail control bellcrank. When everything is perfectly secure (ready for flight), there is about 0.005" gap all the way around the ball in the socket. This slop, believe it or not, is causing the tail blades to have about 5 degrees worth of "pitch slop, which in return, is what I believe is causing these tremendous vibrations in the ass end.

Does anyone have any advise on how I could correct this? I hope everything make sense. If not, please let me know.

Thanks everyone!

[cbergen]

The delrin "cup" can be replaced, It is screwed into the aluminum ballcrank. Typically they do start out a little snug, I have been known to ream the cup just as you would a ball link.

Is it possible this play is result of the vibrations and not the cause?

[soarin77]

Absolutely Chris. I have been working on correcting the vibrations for a while now, so it is definately possible that the initial vibrations caused by previous problems (tracking, balancing, etc) could have let to this root now.

I will give you a call tomorrow to get a new one on order. In the mean time, is there anything in your opinion I can do to temporarily to bandage the problem?

Thanks for your feedback:)