Wobble

[treff]

My hk450 gtpro2 as developed a wobble which I do not seem able to cure. The heli wobbles rapidly up and down.
I have changed just about everything I can think of but it still persists. So far I have changed feathering shaft, main shaft, dampers
blades, main shaft bearings, main drive. The heli is belt drive to the tail which I have also changed. Head speed to me looks good. Most of the stuff on it now is Align DFC head, tail etc. Strangly it does not do this all the time but breaks
into this oscillation for no apparent reason, its more severe flying in to any kind of wind. One more thing this heli as never been crashed, yet. I am
completely baffled so any thoughts, ideas would be very gratefully received. Thanks

[Boggy]

If it is more prevalent in wind I would guess its more than likely too low headspeed.

[treff]

I don't think it's head speed because this wobble has developed over time. Thanks for the reply

[David Drew]

I was going to say head speed too.

Maybe battery is getting pooped and not performing as well.

[Boggy]

Its probably the easiest thing to eliminate too. just ramp it up a bit and see if it cures it

[MarkG_R1]

You don't mention what fbl system you're using, Is it possible you're running on the borderline of too much gain?

If its not that, it there any up/down play in the mainshaft at all? hold the heli down by the skids and pull the head straight up and down, even a small amount can cause the symptoms you're having, My friend has just cured his 450 from the exact same thing, it was a combination of the two

Edit: You might also find it usually happens around mid stick as you go from pos to neg pitch or vice versa

[Grumpy]

You don't mention what fbl system you're using, Is it possible you're running on the borderline of too much gain?

That was my first thought, too high cyclic gains can cause a wobble/oscillation.

[Pj1969]

Sounds like head speed, try in N and in IU1-2 see what happens? Check blade grips too, if they are too tight, that can cause wobbles. Hope you get it sorted

[treff]

Thanks gentlemen for all the very good ideas but unfortunately I have tried them all i'm afraid. In IU I'm running at 100% across the board. Tried the blade grips at various tightness. At the moment I running 3GX V5 which to be honest I set up following youtube video so that could
be wrong. Do I use the gain pots on top of the unit to adjust the gain or go into software? They are all set at the 12 o clock position at the moment. One other thing I have noticed is that when I flip the switch and go into IU 1 the heli climbs rapidly as if there is a pitch change and yet the setup is the same pitch as in N.
Something is set wrong somewhere but I cannot think what it is. Any ideas gratefully received because I've been on this now for over 3 week and its driving me nuts. Thanks

[MarkG_R1]

If there is a fair jump in throttle from normal to iu you will find the Heli jumps up a bit as the faster blades are grabbing more air even at the same pitch curve, no up/down play at all then?

[treff]

I have now added a video of this problem is any one would have a gander. Thanks
Hk 450 gt pro 2 in flight wobble - YouTube

[Pj1969]

I may be wrong, but that looks like to much gain on the gyro, try coming down 5 and see what happens. I'm not up too spec on the 3gx, like you say maybe a gain on the pots. Maybe worth a shot having a chat with Tony on RC help.com, he's knows these like the back of his hand and will help you out, he also has done tutorials on you tubes on setting up the 3gx

[treff]

Thanks pj1969. I also posted there because I am baffled with what is going on.

[Pj1969]

No worries mate, Tony will help you sort it

[treff]

Well problem almost solved thanks to the ideas given here. I was running the 3gx with dampers turned off and acceleration turn up. No wonder it was jumping all over the place. I thought i
had gone over the settings on this heli after updating firmware bu getting old I had infact looked at the wrong chopper DOH! I must give up the red wine. Anyway just one problem which
is very slow nodding, nothing violent just slow nodding in the hover. If any one can help I can get back to some flying. Many thanks.
Update....................................The cause of the wobble is a distorted blade grip that was stopping the bearing from seating properly. More spares on the way. If no cure then it's
Dusty Bin time, probably where is should have gone some months ago. Cheers