Tail twitch and wag with Silverline Vbar

[lou70]

Hey guys,

I've been battling a twitching, wag issue with my N7 and vbar silverline for quite some time now.  Before I rip it down and check every bearing, shim, etc.. I was hoping I could receive some other suggestions of what the issue could be.

Thus far I have re-sized the tail pitch links, reset tail (thanks Drew!), swapped silverline sensor mounting tape, tuned the motor from rich to just about lean, messed with tail gain and still continue to experience an unhappy tail.

I'm suspecting a bad sensor, excessive engine vibration from the engine even though my os105HZR appears to be running very well or some tweaked rotating part that I haven't discovered yet.

Any thoughts are welcome.

Thanks. 

 

[Mike Spano]

sounds like you have your basics covered. a few other things to check/try....

1) bump your HS up and/or down 20-30 HS at a time and see how that goes. not all engines are the same some like a little more rpm, some like a little lower to find their happy place. i deal with this with gasser motors all the time, you would be amazed at what 30HS difference can do, that translates into a larger engine rpm obviously...

2) be darn sure your gov is actually working. i set my throttle curves up so close to the gov HS, it is hard to tell if i have a gov issue. the main sign to me....a twitchy, agitated, or otherwise unhappy tail. i actually ran into this just  this week with my N7. i accidentally got some programming off in the vbar and my gov was not working properly, the instance i saw that tail unhappy, i knew exactly what was going on.

the vbar is an amazing FBL, you really shouldn't have any tail issues. not with the silverline on a nitro anyway. it seems to be the best to me dealing with the tail, and raised vibration levels with nitro and gas. it just holds well without question.

is your fuel tank happy, or foaming up?

[Roger]

If you have the gov engaged I suggest that you turn it off and set up a constant Headspeed with throttle curves.  Doing this will take the gov out of the picture.  A gov that is hunting can cause havoc with the tail.  If it is wagging and bouncing about then you need to concentrate on the air frame.

ROG

[lou70]

Thank you Gasser Mike.

1) I haven't messed with the HS since my initial setup.  I'm not home at the moment but I believe I have normal with no governor, idle1 - 1850 and idle 2 -1980.  If the weather cooperates this weekend, I will give it a shot.

2) Now this is a good point.  From what I'm seeing and hearing, I believe the governor is working but how well is the question.  I have made modifications to the governor gain and minimum governor % with little to no affect.

I have seen the tank foam up a bit.

[lou70]

whitehedr,

I have thought about disabling the governor all together but,  in normal mode I have the throttle curve below the Governor min value so in theory it should be off but I'm still seeing tail twitches.

[Mike Spano]

foam in the tank when you are flying at your governed HS is a sign of vibration.

Have you gone through the clutch stack and made sure everything is aligned well and move smoothly? OWB in the clutch still in good shape? start shaft still in good shape? (i keep a spare start shaft for everything i have that has one in my bag, quick and easy to replace). things like this.

gov hunting - yes, this can also cause you tons of grief. i have MUCH more experience with gas, than with nitro. it is fairly easy to hear a gov hunt with a gas motor. maybe because the rpms are lower and it is easier to distinguish the sound? i dont know. lucky i have had very good luck with nitro gov so far. thanks to Bill K. for helping me the first go around with my vbar gov. this second shot though i had to handle it all myself. it was a learning curve, i can assure you of that...haha

gov min % is what the motor can pull down to to keep the HS for overspeeding, like in a fast descent with negative pitch. i am not sure that will cause this issue...but i guess it is possible since it is in the control loop.

if it is not mechanical, or tuning, we need someone with more vbar specific knowledge please step in....

[lou70]

I have gone through the clutch stack and eveything is aligned well and moving smoothly.  OWB, Clutch and shaft are new and in good shape.

I can't tell if the gov is hunting or not. Engine RPM sounds consistent to me but I have noticed the twitching and wag got worse once the govenor gain was lowered from 60 - 50%.

Also, I have discovered one of my boom supports has broken away again and the bearing in the lower bearing is a tinty bit notchy.  Hopefully correcting these items will fix things.

Thanks for your suggestions.

[Chris Wall]

Lou,
I have noticed this with my N7 at 1950 - 1960, I am sure that it is just my tuning ability, governor setup, and not having it tuned perfectly.  But at 1900 she runs beautifully, no tail twitch and smooth as silk.  As this is my first nitro experience, I am just leaning it out slowly and bumping the head speed up as I notice the engine running smoother.
Chris

[lou70]

Thanks cwall64!

Once I get my machine back together and the weather hopefully cooperates, I will try adjusting my head speed.

I will not be defeated! 

[Richard Rollins]

Lou,
What I your setup? Servos, etc. I had to really play with my gain to stop the wag. Mine is around 90 on tail gain eith a Futuba bls 256 and its rock solid now .
Rick

[lou70]

IBEPILOT1,


Cyclic Servos:  MKS HBL665
Tail: HBL 980
Throttle: MKS HBL665

FBL: Silver VBAR

Engine OS105HZR with PowerBoost Pipe

Rail Main and Tail Blades.

Tail Gain:  75, 80, 85



Thanks.

[Richard Rollins]

Try increasing your tail gain until you get a fast wag and then back off a few points . That's how I set mine and also they are all same for IU12&3. Rick

[Mike Spano]

my tail gain on my N7 is 90 as well. i am flying a Futaba Tail servo on this particular bird.

[lou70]

Thanks ibepilot1 and Gasser Mike!

Coming from a beastx, the VBAR seems to favor very high tail gains.  Once I get it back together and weather permits, I will try increasing the gain.

Thanks again!

[Mike Spano]

with the silverline vbar, i would refrain from doubling up on the mounting tape. the silver sensor is like the Bavarian Demon, and the Ikon unit, they like to be mounted very firmly and rigid. not allowing for any extra dampening. i do not know if it is the sensor itself, or that they use internal dampening, i know the BD used to use internal dampening, but i dont know about the rest. with these new sensors, i think the internal dampening is not even needed anymore...