Tail fin vibration bottom end, and bearing or strange noise in tail in funnel only

[deepak]

Guys
Can you advise me here please.
I have some vibration at about 9800 rpm on the analyzer. Its the tail rotor. Its spins freely when not engaged to the torque tube. The torque tube is good, bearings in place free and lubed. I had changed the front gear cause I thought the bearings were bad so that is now new.I changed the tail rotor case bearings. It feels like its binding when spun by hand anti clock wise but remember its spinning the belt and main gear.
Im not sure what more to look at.
Suggestions welcome
Thanks
D

[EdinTexas]

My experience has been bent tail drive shaft or bent TT or bad bearing in that order.
Remove the blade hub and blades and spin the drive shaft by hand looking for runout at the tip.
Roll the TT on something dead flat and look for any signs that it's not perfectly straight.
You should be able to find a bad bearing just by rolling it in your fingers.
Did this happen after a crash?

[deepak]

Yes this is a rebuild. new parts used new torque tube and bearings. I will check the tail hub tonight.
Thanks
d

[paulmedford]

D, you can take out my tt and try it in your boom, that way we will know for sure where the problem lies., or you can try my tail box. Let me know, may come up on Sunday

[deepak]

Thanks Paul
Appreciate it man
D

[deepak]

update
I used the vbar analyzer and checked the vibration levels.
with the tail rotor hub on there were high spikes at 7800 rpm. When I removed the hub vibes disappeared. I serviced the hub found a notchy bearing and reassembled it replaced the blades just in case they were out of balance.
Still vibration. Im wondering if the bearings in the tube are in the exact place as the manual states. It may be off slightly. Will check and re assemble.
Will post findings
Thanks
D

[galensk]

having a similar issue here... also rebuild after a crash.
did you resolve the problem yet ?
thks,
Kurt

[deepak]

I changed the bearings in the tail case and the gear box.
everything seems smooth. It still vibrated, switched the o rings in the head and serviced truss bearings, vibes less, changed tail fin to a more rigid one. vibes gone
Guess what! esc cutting out now. Changed out esc and now notice short in tail servo(arch burn) on tail servo case. cout not save her. Frames need to be replaced.......... more when I start the re build ....... Gotta love this hobby
d

[galensk]

Sorry for to hear from the crash... but thanks for your report. Good luck with the rebuild...