Head wobble at medium head speed - adjust dampening?

[Habanero]

Hi guys,

I'm also proud owner of the E7 now. Have a bunch of flights on it now and I really love this machine. Swash geometry is perfect for flybarless and the heli is running so super smooth. Thanks to Matt Botos for this perfect helicopter. Anyhow, I still have a little issue:

In the headspeed range of apprx. 1600 - 1900 the heli starts to shake the more or less. It's not of high frequency but you can clearly see from the gear struts that the whole heli is shaking/wobbling. Flying below or above this headspeed range everything is OK.

I'm quite sure it has to do with the (non-existent) head dampening. I've already read a thread here in the forums about shimming the head the more or less. My heli is out of the box with 0.5 shims and I think with the old "super solid" dampeners. It's pretty cold here in Germany. Today it had -2 deg Celcius out on the flying field. When the heli is standing outside the aluminum shrinks a little and there is a good amount of vertical inplay on the blade grips. When the heli is inside the house I'd say there is nearly zero inplay. So question is, should I get even thinner shims as it is still not enough inplay or is exactly this the problem, that due to the cold temperature the inplay is getting too much? As the heli is quite new I can't say if it would be better when it's warm outside and the inplay is less.

Or should I try to get a new set of dampeners as I read currently sold dampeners are made of different fabric. How can I see if I've "old" or "new" dampeners? Do the new dampeners have a different ordering number? Or how can I see if these are the correct ones when ordering them or after getting them!? All I did find at different shops are these: Synergy Solid Head Damper Set (2) [SYN-606-803]. Some other only sell True Blood Dampeners. I only know these from my T-Rex and these are really super hard. I doubt they'll work for my intended application.


thanks for giving me a hint

best regards

Stefan

[flyalan]

What flybarless unit are you using? You may want to check your head gains especially aileron gain. Try lowering it just a bit. At 1800 my Helicommand causes what you are describing. Raise the headspeed above 1850 and all is good. Lowering the overall head gain stops the oscillations.  I don't run less than 1850 except on normal mode when I first spool up so its not an issue.
What gains to adjust may depend on your unit.  It may not be a head dampening issue.

Cheers
Alan


Sent from my iPhone using Tapatalk

[Habanero]

Hi,

my setup in detail is:

Kontronik Pyro 30-12 Motor w. 12 tooth Pinion
Kontronik PowerJazz ESC
12s packs from 3600 to 5000mAh
Swash servos Futaba BLS351
Savox 1290 tail servo
running all servos @ 6Volts
Radix 690SB mains
Rotortech 115 tail blades
I'm using ThunderTiger GT5 Flybarless unit.

Already lowered the gain to 50% and even tried flying with 0 Proportional gain. Doesn't change anything regarding the wobble.


thanks

[RichL]

Hi guys,

I'm also proud owner of the E7 now. Have a bunch of flights on it now and I really love this machine. Swash geometry is perfect for flybarless and the heli is running so super smooth. Thanks to Matt Botos for this perfect helicopter. Anyhow, I still have a little issue:

In the headspeed range of apprx. 1600 - 1900 the heli starts to shake the more or less. It's not of high frequency but you can clearly see from the gear struts that the whole heli is shaking/wobbling. Flying below or above this headspeed range everything is OK.

I'm quite sure it has to do with the (non-existent) head dampening. I've already read a thread here in the forums about shimming the head the more or less. My heli is out of the box with 0.5 shims and I think with the old "super solid" dampeners. It's pretty cold here in Germany. Today it had -2 deg Celcius out on the flying field. When the heli is standing outside the aluminum shrinks a little and there is a good amount of vertical inplay on the blade grips. When the heli is inside the house I'd say there is nearly zero inplay. So question is, should I get even thinner shims as it is still not enough inplay or is exactly this the problem, that due to the cold temperature the inplay is getting too much? As the heli is quite new I can't say if it would be better when it's warm outside and the inplay is less.

Or should I try to get a new set of dampeners as I read currently sold dampeners are made of different fabric. How can I see if I've "old" or "new" dampeners? Do the new dampeners have a different ordering number? Or how can I see if these are the correct ones when ordering them or after getting them!? All I did find at different shops are these: Synergy Solid Head Damper Set (2) [SYN-606-803]. Some other only sell True Blood Dampeners. I only know these from my T-Rex and these are really super hard. I doubt they'll work for my intended application.


thanks for giving me a hint

best regards

Stefan

Stefan, at the head speed you are running you will likely see a small amount of vibration.  There are few things you can do to fix this problem.  Lower the head, this will require shorter link rods, softer dampenrs, or increase or decrease your head speed.  I ran into this problem running 8S on my E7.  Changed the dampeners vibration gone.

Rich

[Habanero]

Hi Rich,

where can I get softer dampers? You have an ordering number?

thanks Stefan

[Habanero]

Hi guys,

problem solved  :

bought a set of different 8mm shims and firstly added additional 0.1mm on both sides. Blades grips can still move vertically but there is no horizontal inplay now. Did a few flights today in the wobble is totally gone. Amazing what 0.2mm can do. Also the temperature is +10 degrees here now. So also no inplay when the heli is outside...


Btw. I have been wrong, there are already 1mm shims on the head, not 0.5 as said in the first post. And I think I already have the soft(er) dampening as you can easily squeeze the dampeners with two fingers. As there is no slop anymore you can feel that there is dampening when moving the blade grips, now. The head definitely is not dampened so hard. Even much softer than the dampening on my T-Rex 700 which has lime green KDE dampening (which is rock solid but does not wobble, too).

So maybe I even will try to add thicker shims and make the head more aggressive. In conclusion I'd say problem was the huge amount of inplay so the spindle could flap loosely and the dampening was not compressed enough to work correctly.

[flyalan]

Those were 8mm shims?

Alan


Alan Butler
Team Synergy