Fixed tail vibration

[sp00fman]

I have just (hopefully) fixed a pretty severe tail vibration on a new build plastic 425.
Everything is smooth until i hit 2500rpm. When I increase head-speed even more it gets much worse, the tip of the vertical fin vibrating sideways about 3cm and i got worried it would hit the tail blades at some point.

Things i changed, but got similar results:

-new tailshaft
-put on the X5 tail hub+grips
-back to stock tail blades (tried with the 550 tail-blades first)
-adding different lengths of tape to one tail blade to see if things get better

The thing that fixed it was just tightening up the belt. This does increase friction somewhat, and it stops a bit sooner when spinning the head (without blades) by hand.

Thinking about why this would fix it, i came to the conclusion that the belt is giving tension on the tail shaft, tightening it on the bearings a little.

Sure enough after inspection i found wear marks of the tail shaft rotating in the bearing inner race.
Grabbed a new set of bearings ( to be sure) and glued the inner race on the shaft with anaerobic retainer.

Tail spins up free of vibrations, even with a pretty loose tail belt. It even rattles in the boom a moment when spooling up, but stops soon. I suppose that is all right.



Just want to share my experience. Was about ready to give up and ask for help here.
Glue your tail bearings guys

[PTcaflyer]

...I had that too with a stock tail case and X5 grips...shook so bad it threw the link pins out of the slider...case was cracked...Put an X5 case with new Brgs and run the 550 tail blades...SMOOTH AS BUTTER!

[Jerrymac]

Hmmmm, I am having the exact same problem with a fairly new build that has less than a dozen flights on it. The vertical fin vibrates so bad it looks like it is going to break off. It did this right from the maiden flight though.

I was thinking maybe my main blades are not balanced perfectly, but I guess I will give the tail a look over too.

[PTcaflyer]

Yep...check it closely...it appeared o.k. until I twisted it and the crack opened up...the faster it spun, the more torque would twist it...I made a G-10 "stiffener" for my CF Vert. Tail and now it wouldnt flutter even if I tried.
PT

[minititinflyer]

i had the same problem for a bit but i got new tail blades kbdd 70mm .and checked over my links to see if there where tight sized them. and put some grease on the dampers and it stoped for me. i also found the oneway bearing comes dry as a bone in a new kit poped some stuff in there and its smooth as ever

[blade_crasher]

Speaking of lubrication of the OWB. What is the correct stuff for that? Is aerosol silicon ok, or light "sewing machine" oil, or something more like silicon grease?

I got some of my 550 parts and put the new tail boom on. The boom support rods that go down to the bottom of the rear landing gear now seem sort of "short". Do I need to extend these rods by replacing the aluminum with a longer part or some type of CF rod mod?

[PTcaflyer]

OWB needs to be almost "DRY"...light oil or a drop of ATF, then swab it like your gun barrel(oops! wrong forum!) I use Scorpion oil too...
The boom supports are all the same length( I Think..) but the X5 supports area little longer...I use the stockers on all of mine...

[Jerrymac]

Don't over lubricate the OWB as it may cause problems. I have read of many failures on here, although I don't know for sure what caused them. I put a couple of drops of ATF on my OWB's during assembly. So far, 4 years and 4 different Hurricanes and I have yet to experience a OWB failure.

Also, during assembly, DO NOT put 2 washers on the OW shaft. Put only one washer below the OWB. I think many of the OWB failures were caused by the top washer wearing and the tiny metal bits dropping into the OWB. (Just my opinion, not sure why so many people reported OWB failures).

Tail boom supports are the same for the 425/550. Just move the part on the boom closer to the frame until they fit.

[sp00fman]

My OWB did come lubed, so i left it alone.

Other things i noticed on this newer kit are that the tailshaft pulley can move a tiny amount sideways in the plastic tail assembly. I placed a thin washer between it and now the tailshaft bearings are slightly pre-loaded. This makes it less sloppy.

Other things i noticed is the canopy mounts are a new style, the tail grips are held by a locknut instead of a screw. Did find one small problem on the main head. I needed to flip the featheringshaft screw spacer for high damper compression to take the slop out of the main grips.

Otherwise a really smooth build, except the tail bit

One thing i need to keep an eye on is the auto-rotation assembly heating up. it feels quite hot when i feel it after a 5 min flight.
Will take some measurements soon.

[minititinflyer]

Originally Posted by blade_crasher

Speaking of lubrication of the OWB. What is the correct stuff for that? Is aerosol silicon ok, or light "sewing machine" oil, or something more like silicon grease?

I got some of my 550 parts and put the new tail boom on. The boom support rods that go down to the bottom of the rear landing gear now seem sort of "short". Do I need to extend these rods by replacing the aluminum with a longer part or some type of CF rod mod?

look for one way bearing grease its the best stuff to use no oils. it dosent gum too. bc i use it on all my helis and there smooth as ever.

[sp00fman]

Hot drivetrain is solved with a little WD40 on the main and front gear. Gears are 10°C above ambient, batteries and motor 15°C after 5 minutes sports flying.

[tolenca]

Hi, may I ask you what "anaerobic retainer" did you use? I have that vibration after 2400 rpm

Thanks in advance.

[sp00fman]

I dont think brand name matters much. many just call it green loctite.

This is the one i have. I really hate/love it. The stuff is EVIL. Only applying heat will get get my bearings off the shaft again.

[tolenca]

Thank you.

Later

[sp00fman]

Oh, my bad. this is the actual one i got for this use.

http://www.hobbyking.com/hobbyking/s...Strength_.html

pm send

[tolenca]

ok..thank you again

[sp00fman]

Got all bugs out of the heli and it is flying really well.

Got my first real flights in, pushing it a little more. I'm still taking it easy, not used to this size heli yet. Adrenaline was pumping really hard at the end of flight one.

It really cracks the sky open
The SK3 1600KV is holding up really well. Very happy with that motor.
The nanotech 25C 6S3000 turned out to be a good choice. It fits and balances out with the servo on the tailboom.

YouTube

YouTube

YouTube

YouTube

Next flights will be with my second Gaui. Stretched flybarred 520mm. Its ready to go tomorrow

[PTcaflyer]

...Beautiful!
Not a thing wrong with that one! I could hear the "Grin" in you audio!
PT