450 Trex 450 Pro Tail Rotor Hub

[Bruno]

Had a crash that smacked the tail. During repair I isolated a vibration in the tail. Upon examination found the tail grips wobbled on the rotor hub. What I may have found is that one of the bearings was damaged (hard to tell).

Inner race of the grips are smooth and symmetrical.

However, if I grabbed either tail rotor grip and torqued them by hand I noticed a wobble of the grips on the tail rotor hub.

Here is where I need opinions. It was difficult to get the bearings off the rotor hub shaft (very tight). Is this typical?

New bearings are also pretty tight on the rotor hub. Is this typical?

Have not put it back together yet.

 

[Lee]

Its a bit difficult to understand what it is thats happening. Can you make a 30 second video demonstrating the issue?
Bearings should be snug but not tight to get on and off unless you have bearing thread lock on them.

 

[Bruno]

Sorry, no video.

I found one of the outer tail grip bearings to be quite gritty. I replaced the bearing and it eliminated 80 percent of the tail vibration. I still get a good amount of vibration at mid throttle which is quite noticeable. I can actually feel the vibration while holding the boom and see the vibration in the vertical fin. I am going to check the tail shaft straightness and it's bearings. Running the tail without the blade assembly the tail shaft seemed straight and there was 0 vibration.

Is there any chance the lack of "flatness" of the main great (which is visibly evident) is translating to the tail vibration?

 

[Lee]

Is it a torque tube version?
Where did you place the bearing on the tube?
If its equidistant from the front as it is to the back, you may have a resonant frequency.
It need to be off centre.

 

[Bruno]

It is a TT version. The bearing is off center toward the front as per the manual.
However, I am going to try a new TT.