Tail wag with BK 8005 tail servo

[lou70]

Anyone experiencing slow tag wag running BK 8005 tail servo?

[Rodney Kirstine]

That's the servo I'm using and haven't had any issues.  Everything moves freely and smoothly with the control rod disconnected from the servo?

[lou70]

Yes, everything moves freely with the control rod disconnected. 

I have read a handful of posts on helifreak with others having similar issues on other air frames as well.  Perhaps my 8005 needs to be sent back to BK for inspection.

[Greg Jackson]

Did you ever use the servo on a different heli and have any issues? Or have you used a different servo on the 766 without issues? I am running BK tail servos without issues.

[Mike Spano]

Ok, 2 things to remember always....

1) fast wags are 90% of the time gyro settings.

2) slow wags are 99.9% of the time a mechanical issue.
        A) Something too tight
             i) links not fitted properly
             ii) output shaft not oiled properly
             iii) tail pushrod guide kicked out and binding on Teflon heat shrink.
         B) bearing binding
              i) installation of thrust bearings incorrectly.
              ii) radial bearing having issues  (in my experience the most unlikely possibility of them all)

Check mechanical issues one more time extremely closely. If there are none, get a different Servo and try it.

[curmudgeon]

I was experiencing bonafide tail blowouts on my newly built Synergy 806.  I've never ever experienced a tail blowout before.  Prior to this heli, I had built and flown a Synergy E5, Synergy E5s, Synergy E7SE as well as T-Rex 550, T-Rex 600Pro, Goblin 570, Goblin 380, MA Whiplash and a few other helis.  Never a tail blowout.  After many members (both here and on HF) recommended replacing the tail servo (a BK BLS-8005 HV), I finally relented and purchased the X8 MKS HLB880 tail servo along with a special order [O0002015-6] servo arm (16mm hole length with 3mm hole thread), and my tail blowout issue resolved instantaneously.

[lou70]

Did you ever use the servo on a different heli and have any issues? Or have you used a different servo on the 766 without issues? I am running BK tail servos without issues.

Greg, this servo was purchased new for this build. Are you using the same servo on your 766?

[alan]

I am the person that encouraged Curmudgeon to replace the tail servo. Why you ask? Due to experience with this servo!  I have a friend that has tried using it on two occasions. He used this on both a Urukay and the 766 and in both cases he had to deal with a tail wag. He could never get it tuned out.  Replacing the servo solved the problem in both cases.  There have been some reports regarding this phenomenon.  I thought this was a more isolated problem? I have used this servo with success though.

In this case I would replace the servo to at least rule it out.

Cheers
Alan

[curmudgeon]

Delete

[lou70]

Ok, 2 things to remember always....

1) fast wags are 90% of the time gyro settings.

2) slow wags are 99.9% of the time a mechanical issue.
        A) Something too tight
             i) links not fitted properly
             ii) output shaft not oiled properly
             iii) tail pushrod guide kicked out and binding on Teflon heat shrink.
         B) bearing binding
              i) installation of thrust bearings incorrectly.
              ii) radial bearing having issues  (in my experience the most unlikely possibility of them all)

Check mechanical issues one more time extremely closely. If there are none, get a different Servo and try it.

Hey Mike,

I have checked everything a number of times thus far.  Everything is at least on par with how my N7 feels right now.
This is why I'm thinking it could be my servo at this point.

[curmudgeon]

I wasted many days and flights trying to resolve the tail blowout issue.  Simply replacing the tail servo with true and tried tail servo solved the issue.  My best guess is that the BK servos may suffer from inconsistent quality from batch to batch.

[lou70]

I wasted many days and flights trying to resolve the tail blowout issue.  Simply replacing the tail servo with true and tried tail servo solved the issue.  My best guess is that the BK servos may suffer from inconsistent quality from batch to batch.

Thank you curmudgeon! I reached out to BK and they have asked that I send in my servo for a replacement from a newer batch, which according to them resolves the issue.

I will keep everyone posted with my results!

[Greg Jackson]

Also, maybe try the 7006 servo. Depending on your setup, the 8005 might have some odd tendencies with other brushless servos.  But again, there are a ton of other factors for that to be true.  I had an 8005 that had something odd occuring, tried a 7006 and everything was perfect.  But, I have a 8005 on a heli that never had blow outs or "weirdness".  So, my last comment is that there are many different things that could cause the issue and it should not be the game of blame the company; especially since they are providing good customer service to help fix the issue. This comment is not directed to Lou or anyone specifically because no one on this thread has stated anything about this particular brand being bad.  But, this statement is for anyone that might read this thread in the future.

[Greg Jackson]

Did you ever use the servo on a different heli and have any issues? Or have you used a different servo on the 766 without issues? I am running BK tail servos without issues.

Greg, this servo was purchased new for this build. Are you using the same servo on your 766?

I am using the 7006 on my 766 with 7002 servos. On my E5 I used the 8005 with 7001 servos. 1000s of great flights. But I'm not saying that the component is not causing a problem for you, because anything (esc, motor, bec) could possibly fail.  But I truly believe BK will do everything to help you get things sorted out. 

[mc20piece]

I am the person that encouraged Curmudgeon to replace the tail servo. Why you ask? Due to experience with this servo!  I have a friend that has tried using it on two occasions. He used this on both a Urukay and the 766 and in both cases he had to deal with a tail wag. He could never get it tuned out.  Replacing the servo solved the problem in both cases.  There have been some reports regarding this phenomenon.  I thought this was a more isolated problem? I have used this servo with success though.

In this case I would replace the servo to at least rule it out.

Cheers
Alan

I've absolutely had the same experience with the 8005. I fought it for weeks thinking it was mechanical and finally replaced it with a Futaba 276, problem gone.