N5 tail control rod resonanates ashead speed increase

[Paul66]

Hi Guys
Had to rebuild N5 this weekend after a tail blade broke( KDB blade hole elongated and snapped across hole) did not do much good for the rail mains.
Back on topic now rebuilt control rod for tail vibrates as head speed increase, cannot see any evidence of anything out of balance swapped tail assembly from E7 and this eliminated resonance, so clearly appears to be related to tail drive area, all looks good bearings, tail shaft straight, blades new and balanced. Where to now?
any common areas that wear out?
This machine has seen considerable service but still like how it flies when in the air.

[Ross Lawton]

Hi Paul66,

Sorry to hear of the crash, but lets see if we can get this sorted for you.

When you rebuilt the tail assembly did you replace the tail output shaft and tail rotor hub? When a tail blade fails and is ejected from the tail rotor assembly the resulting shock and imbalance can damage the shafts and rotating parts. Usual things to check if this happens is the tail output shaft, tail rotor hub and also the bearings on the tail output shaft and in the tail rotor grips, including the thrust bearings.

Let us know how you go and hope this helps,
Cheers,
Ross

[Paul66]

Hi Ross
thanks for the reply I have a trex 600 tail hub that I can cross reference against , I would use the E7 but different diameter, I'll get new bearings and replace in blade holders, strangely enough these are trex metal holders previous owner had upgraded to from the original plastic synergy ones. I'll also get another shaft and replace and see what happens from there.
its probably time to upgrade tail again to a N5C 6mm shaft etc.. but this may be a little costly.
Thanks
Let you know how I get on hopefully be able to test this weekend and get an outcome.

Cheers
Paul

[Jon Mills]

Hey Paul I say plus one on the Remove Replace tail shaft and rotor hub. I have had a shaft that dial indicated .001" out and it caused a sick vibe.  Also make sure you replaced the spacers on both and the same part on each grip.  One more thing I can think of is and this goes on the same basis of having the same parts in both grips is make sure you get the nuts inside the grips that attach the grip to the hub tightened down till they start to bind then back off a little till they move freely.  This will ensure you have the grips almost exactly the same distance from center.  This is the most important, a small deviation from exact will cause a serious vibe. Hope you get it sorted bud keep us updated.

Jon Mills

[Paul66]

Hi Guys
thanks for your help, I have tracked down the source of the vibration.it appears to be a number of factors all around tail shaft which like Jon mentioned is only .001" out, but there is also a little play in the shaft to the tail flange bearing, I noticed a post some where else maybe from Matt regards loctiting  the bearing to the shaft but hopefully the new shaft should be a better fit, hub and bearings all look and feel ok but will swap as a matter of course. It may be time to retire this old bird and update to a new N5c or N7 which looks mouth watering.
It hard to let go and stop using when it keeps coming back for more punishment especially only being a relative novice it has seen it fair share of the dirt. But this thing is remarkably resilient and never had to replace any side frames, only boom and usual suspects shafts, bearings and tail fin.

Cheers

Paul