Trex 450 tail swing / hunt - desperate

[cilliers]

I am experiencing some difficulty in determining the cause of a newly acquired tail swing with my Trex 450. I am using a Futaba GY240 Gyro and once gain is setup to above +75% I experience the expected tail wags (hunts) and after a while hovering the tail may swing 30 to 90 degrees. If gain is set lower the tail still wag somewhat but slower and after about 3 or 4 wags it swing around abruptly by 30 to 90 degrees. I have changed gyro, motor, ESC, crystals, receiver, main shaft, checked all gears for missing teeth, slip – everything normally associated with above problem – no change. Did anybody experience the same problem before, any suggestions?

[Daz(DJLFlapper)]

Is this a heading hold gyro, if it is have you made sure that the revo mix is inhibited/off. I can only think that maybe the servo cable or the receiver cable is loose internaly if the revo is not a problem.
Many years ago I had a PG03 that showed simular problems and found that the gyro cable that went to the receiver was actualy only rubbing against the solder point.(when I opened the gyro up) when I re soldered it I had no problem and it is still good to this day.

[turco]

Also make sure that your ESC is not close to your Gyro. they should be farthest apart from each other.



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[cilliers]

Thanks guys, I eventually found the problem. It was one of the tail rotor grip bearings that were binding only under load. This caused the gyro to over react as more force were needed to adjust the pitch.
Not a normal fault you would expect.

[hawkman]

Check the pitch control linkage is nice and loose too......the rod from servo to pitch contoller.....you should be able to rotate it...or wiggle it on its ball mount.

Check out this site for advice too.

www.trextuning.com

really good site this one

Rob

[cilliers]

Thanks yes that was one of the first thing I checked. I agree an excellent site