Frustrating vibration

[Kyle O.]

Hey guys, my n7 was smooth, until I hit the tail lightly during an auto. I spun the Heli around and it still had some motion going backwards, not much, but then the skids caught just a tad and stuck the tail in the dirt. Just where the blades touched the grips and put a nick in the root of the blades.  I rebuilt the tail including bearings in the output housing and output shaft, thrust bearings and grip bearings, including new tail blades. It still is vibrating, all gears  look good, I guess I need to inspect the torque tube. I'm just frustrated.  The Heli was smooth as silk before the strike.

[Josh Easter]

Yes defiantly pull the tourqe tube and inspect it. If it was a light hit like you say I doubt it bent to tube but you could have one of the tube bearings come off. That would be the next place to check. Good luck!

[Jon Yarger]

Check the shaft in the tail transmission. I have seen that shaft bent causing vibration.

[Richard Rollins]

While your checking things also check the front transmission gears. Make sure you also have the OD,s on the thrust bearings correct, all this cound cause what your seeing.
Rick

[Kyle O.]

Yeah didn't get too involved in replacing stuff because it seemed like such a light strike. I should have dug in deeper when I saw the tail output shaft was straight.  All the gears looked good. But I will pull the front transmission out and inspect it as well as the torque tube bearings. 

[Danny Dugger]

Check gear mesh. If the tail isn't pinned at front and/or rear it could have been pushed in causing either the front or rear set of gears to bind a little.

[turner2]

Kyle ,Did the main blades touch the ground. I did the same thing last year to mine .I did a complete rebuild on the tail still had the same problem. Although I did not damage the main blades . I decided to pull the spindle shaft out of head. It was bent pretty bad then pulled the main shaft out it was only bent slightly. Replaced both of them and she is smooth as silk now. 

[Richard Rollins]

Its usually a safe bet to go ahead and replace those normal items when you have those tip overs. i think we all  find out the hard way.

[Kevin Feil]

Even though you were doing an auto and not on the power, I would verify your Radial bearings in the Tail Box, the Radial bearings in the tail box side plates (tail output shaft runs through)as well as the Tail Spindle. I have seen either of these become compromised regardless if you were doing an auto or full on power. As fast as that tails turning, you have a bearing in distress in any way, it's magnified through the heli, picture a tuning fork when you hit it on something. Also from experience with RC and full scale Helis, always go completely through the machine regardless of how soft you think you landed or regardless if there is no visible damage, these are the type anomalies that will drive you crazy.. Good luck and look forward to hearing what you come up with.

BR,

K

[turner2]

I have found that if you push the boom in futher than flush with the front support it will jam the torque tube between the rear pinion and the transmission pinion and cause a bow in the torque tube. This will cause a rapid bounce up and down with the tail. This looks like a vibration and is hard to pin point. If the boom moved forward it will cause exactly what is described unless you have both ends pinned.

[Kevin Feil]

Charlie, that's a damn good point !! Good Intel brother.

K

[Kyle O.]

I got it squared away. It was not a mechanical problem as far as drive train.  I replaced everything that turned in the tail, problem still existed.  Okay so I went looking at the engine, didn't find anything. Went to take apart the carb, then I saw it, the mid needle, well let's just say lack of a needle because the tip was no longer part of the needle, it was resting inside the body of the carb. So my vibration was just a rich issue.  I didn't notice it when the engine was running because with the mid range it never really shows a rich issue because I run it fat on the mid range anyway. It was just four stroking and causing all kinds of harmonics thru the airframe.  Man I was shocked.  Thanks for the help, I guess it's just one of those coincidence things that happened all together.

[Kevin Feil]

Well Kyle, congrats on your find and congrats on a possible solution that may help others.. Glad your up and running brother..

K

[Kyle O.]

It was one of those things that you never expect to find, I flew a gallon today and all is smooth.  I think this issue happened because of the needle issue with the o.s. 1.05.  Where the main needle body was too big and I had them turned in to where the mid needle was making contact with the body, but not leaning it out enough because of the main needle being so rich. I think that slight interference between the needle and the body is what caused it to fail, it had a polished area right where it broke.  I just replaced them with the updated needle bodies and it runs like a sewing machine now.

[Kevin Feil]

Absolutely Awesome, glad your having fun brother..💪🕶

K