600 Trex 550E DFC V3 Vertical Fin Vibration???

[Bruno]

The heli is stock except for KDBB ED Lime Green dampers and tail boom support brace. The head and tail rotor system are buttery smooth.

I noticed that the verticle tail fin has a high frequency resonating effect / vibration during flight/hover while in idle up mode at 85% throttle (don't know the head speed) and maybe 5 degree pitch. There was no tail wag.

Is this tail fin vibration typical/normal? If not, what should I check?

Thanks.

 

[Bruno]

I examined the tail setup closely. All connection points are well secured.
However, the tail grips have some play on the feathering shaft and the tail blades have some lateral play within the grips. This tail play was there at the time of the build and was referenced in other posts.
This heli had only about 15 gentle flights so I doubt the bearings are worn/damaged.
I had balanced the stock tail blades and did have to add weight. I use a precise blade balancing system utilizing a common blade root point for identifying blade center of gravity and counter weight positioning.
I am going to try another set of new Align 90mm tail blades.
I carefully soon the TT without noticing any vibration.
Funny to compare this problem to my 130X but that little bird's tail vibrated until she got the right set of lynx tail fins.
All suggestions are welcomed.

 

[murankar]

If you have play in the grips you need to try and work that play out. Everything should be snug but free moving. if that's not the case then I don't know what else to check. How much vibration do you have?

 

[Bruno]

If you have play in the grips you need to try and work that play out. Everything should be snug but free moving. if that's not the case then I don't know what else to check. How much vibration do you have?

The vibration is only noticeable when watching the vertical fin during a hover which only resonates within the tail fin and does not translate to the tail boom.

That is the amount of play since original set up. I just measured it and there is less than 0.5 mm outward movement of the tail grips and probably the same lateral movement. I would think centrifugal force would eliminate the play during flight.

Do you think I should throw spacers in there?

Interesting since the head had play from initial build as well until I swapped the dampers for KBDD ED Lime Green dampers. I was preparing to throw spacers on the feathering shaft. I had great concern with the head due to reading horror stories with the DFC links breaking.

 

[Derek]

I had a similar issue with the tail grips on my Trex 500. During a hover, the tail wasn't wagging, but it was hunting around. No amount of gyro change seemed to help. I got looking at the tail grips and I noticed that there was quite a bit of lateral movement in the grips. I ended up getting a CNC aluminum tail assembly from a buddy, here on the forum, and I installed it on my 500. Hovering after adding the new tail assembly was perfect.

You can try to add spacers to the grips but when I tried to do that, everything got bound up and wouldn't move at all.

 

[Bruno]

Simple test: this may have started after I installed boom support brace. I wonder if without the brace the boom supports would soak up some of the resonance.

 

[Bruno]

The TT bearing dislodged from the TT and the TT bearing holder was loose in the boom. Used epoxy this time for the TT bearing instead of CA. Also found that the shield of the rear rotor shaft inner bearing dislocated from the bearing. Replaced that as well. Will reassemble tomorrow.

PS: checked TT trueness. Looked good.

Thanks All.

 

[Lee]

Resonance can come from just tightening the boom clamp slightly harder or looser than last time. Play with the tension of the bolts, obviously enough to secure it in place
If its just a slight vibe in the tail fin, then thats ok, but if you can here a humming noise, then resonance from the tail unit could be effecting things.
It could be something simple as changing the tail blades to another type. I changed from plastic to carbon on one heli which stopped vibes.
A bit of play in the grips is ok. As you said centrifugal force will throw them out. My 600 and my Warp 360 have play in the grips, but both fly perfectly.

Good luck tomorrow.

 

[Bruno]

That was it. The TT bearing dislocation from TT and rubber bearing holder. Replaced TT bearing (epoxy instead of CA) and replaced the rear blade shaft bearing holder bearing (see pic).


This rear bearing was a bit more challenging with regard to removing the bearing. Evidently, this part is not sold separate from the tail assembly (H60249 600METAL TAIL PITCH ASSEMBLY) which is about $45.

She is now vibration free. Stock tail fin is solid.

Thanks. All.

 

[Bruno]

Fixed.