Wierd Tail Transmission Issue

[lperagallo]

I was going through the EB in the garage since flying in 30 degrees and 30MPH winds is not that appealing to me today. I decided to double check the tracking of the tail blades. Turns out they are fine.

What I did see surprised me :shock: As I turned the main rotors the tail transmission moved up and down a bit. It also does some slight right to left movement also. :bomb: The bolts holding the tail are tight. What is bent? Is it the torque tube shaft, the shaft that attaches to the torque tube? What steps do you take to figure this out? What else might cause this? I guess this explains the elusive small vibration I've been trying to track down. I'm sort of stumped. :dontknow

[lperagallo]

Update so far on what I've found.

Front torque tube....appears to be straight when rolled on a piece of glass
Center bearing carrier shaft...same
Rear Torque tube...same
Tail drive shaft. one attached to torque tube. appears to be straight but hard to tell
Bearings in center block were replaced on last crash back in November when I did the lawn dart thing :shock:
Bearing in tail case seem fine also.

So...that makes things odd! I would have thought I'd have found something bent. All the collars have three set screws and they were tight. each collar has one hole drilled into mating piece. I'm still stumped :dontknow

[rkeith2]

Is the dogbone into the coupler turning true and you are seeing out of round movement of the transmission?

Do you see any mesh changes in the main gear to tail drive - not running true?

[lperagallo]

There is a little slop when you turn the tail rotor blades and hold the tail gear. But it's no more then a friends raptor 90. There is a bit of forward and backward movement of the tail drive shaft at the main gear. There isn't any mesh change in the main geear to tail drive.

By teh way, I'm talking about the tail rotor transmission in the rear, not the tail drive transmission.

Very strange :arggg:

[rkeith2]

So I assume that after you said the tail blades are in track, the hub would not be bent and be the culprit.

No bent input or 90 degree shaft either but you still see an out or round condition -

Would like to eyeball it :dontknow

[kelly steed]

If your input shaft and out put shaft are not bent,and I think your talking about your input shaft movement,witch conects to your drive shaft I will pm you on the fix.

[lperagallo]

In addition to posting here, I also used the new Bergen website support section. Chris responded to my questions and solved the problem by suggesting it was the tail gear input shaft. While I couldn't see the bend when rolling the shaft on a piece of glass, when I put it in my drill and spun it up it was clear the shaft is bent. :bomb: I guess I bent the shaft back in November when I turned my heli into a lawn dart when a mechanical failure in my tail support clamp caused me to take out the main rotor blades as I descended quickly. Live and learn. :arggg: