N5 Wobble

[j2tgw]

I have got what can only be described as a wobble in one of my N5s
This started last week after a little woopsee !

Was flying at about 20 ft when one of the blade ball links came of .The blade then
spun round and the engine bogged down ! I put on throttle hold and the heli came down
in the long grass at at the bottom of our field !
looked like no damage till i stripped it when I got home and found the main shaft had a
slight bend in it and the jesus bolt on the drive belt pulley was bent
I replaced these and now I have a wobble ?
I thought maybe the feathering shaft was bent , changed that , no diff ,tried diff blades
still the same , main shaft bearings , all the usual stuff , even tried head speeds
still got this wobble

Anybody got any sugestions as to what it might be ??

Help !!

Cheers Tom !!

[debrooker]

How are the main shaft bearings?

[j2tgw]

I have replaced them and still the same

[ROSSCO]

Hi Tom,

Is this N5 Flybarred or Flybarless?

If it's flybarred, check the bearings and thrust bearings in the blade grips for any notchiness, also check the flybar and paddles for any bends of paddle missalignment as this could cause a wobble.Are the blades tracking? if they are not then it might be worth checking the blade grip pitch arms for a bend as this will cause the blades to run out of track and can cause a slight wobble on the head.

If it's flybarless check the blade grip radial and thrust bearings for any notchiness.

[j2tgw]

Hi Rossco
Blades are tracking spot on .I put a new flybar on and diff paddles and its still the same .
I was thinking maybe the dampner rubbers .but there is no play on them .but I have ordered a
new set today from fl will try them and see .The thrust bearings feel fine ,So my next port
of call is to swap the heads over with another one and see what happens .There is no prob
with the other ones !

Cheers Tom !!

[oneandonlyian]

Have you got a head button on? If you have a bolt which is to long fitted it presses down on the feather shaft. Ask me how I know.

Sent from my Desire HD using Tapatalk

[j2tgw]

Thanks I will have a look at that
Cheers !!

[Supercaptaincrash]

Had a identical problem last year on my 600 ! if i remember correctly, mainblades were slightly to tight in the grips and i reapplied grease to feathering shaft and dampers! flew perfect after!

[j2tgw]

Cheers I will try that tommorrow !
Thanks !

[debrooker]

Have you got a head button on? If you have a bolt which is to long fitted it presses down on the feather shaft. Ask me how I know.

just to add, i also fitted a small spacer to relieve the pressure the screw places on the sleeve.

[ROSSCO]

You can actually remove the sleeve alltogether but if it was fine before the crash it suggests that something else is causing the issue.

Here is Matt Boto's notes on the head axle sleeve:
Head Axle Sleeve

I’ve noticed quite a few people with low head speed wobbles and there are a few reasons for this. The stock dampers are very tight in the head as well as on the spindle. The main blade axle must be greased so that it can center properly during flight.
Stock from the factory, the N5 head dampers are compressed by about 1mm. To remove this compression, replace the 1mm shims in the head (between thrust bearing and radial bearing inside the blade grip) with either .5mm shims or .75mm shims. This will allow you to run lower head speeds without the wobble.
I’ve found a few helis out there where the head button bolt was pressing against the main blade axle sleeve! If you are going to run the main blade axle sleeve make sure you do not over tighten the head button bolt, it will run into the sleeve if tightened too much. I personally have stopped running the sleeve because I didn’t see a difference in performance with the sleeve and it can actually hurt your performance if not centered properly. My suggestion….. ditch the sleeve!

[j2tgw]

Thanks for all the help guys ! I have done all the things sugested and the wobble
has gone I dont know what one did the trick , But the heli is brill now !

Thanks again Tom !!

[ROSSCO]

Thats good news!, glad to hear you got it sorted Tom!

Happy flying!

[debrooker]

Good news, now get out there