Tail twitch EB.

[Helisin]

Was out flying yesterday when suddenly my tail had a few intermittent HARD & FAST twitches.(Anti torque-nose right). Only moved tail aprox 12 inches before it stopped Given the direction of the twitch and the fact that it stopped doing it before I landed, I think it's a gyro/servo problem rather than tail drive. I don't believe tail drive issue would come and go.

-401/9254 combo with push/pull upgrade. Set up as per Bergen set-up instructions. Limits are good in both directions with no binding. No real tail drift in non HH and pitch slider centered on output shaft.
-checked backlash and tail drive integrity-seems ok.
-checked non HH and it happened there as well.
-checked on ground no engine running. No occurance or obvious sudden movements of tail pitch. Of coarse!
-tried decreasing sensitivity - no joy.

I thought I remembered someone having a similar problem a while back with possible associated notchy 9254 servo in operation. My (9254) feels fine when rotated with no power but when powered up and controls moved it does translate to kind of a notchy movement on the T/R blades as opposed to smooth like the 8311's on the other flight controls. Then again on the ground there isn't any real load on the 9254 which may give that effect.

Maybe tonight I'll try running the servo direct to Rx without the gyro. Sorry for the length. Thanks in advance for any input.

Rob.

[Gary Travis]

Rob check the gyro mounting tape to make sure it is not coming apart. Second did you here any engine change such as a rich condition (misfire)
Gary

[lperagallo]

I don't think that Bergen recommends using the push/pull system with a 401 Gyro set up.

Lou

[Helisin]

Hi Gary. Thanks for input.
-Gyro tape(green Zeal) is secure.
-No misfire noted. Nice 'n smooth. A few days prior I had a misfire or two with tail twitch(much smaller twitch and tail to the right). I found the fuel feed line was introducing bubbles to carb. Replaced line and it was just like when I was in Utah. Nice'n smooth again with no misfires or abnormalities.
-As well I had a look at the servo gears. All are good.
I'll get out tomorrow and see what else I might find...

Lou, thanks for the input. I learned of this a while after I purchased my kit in March 2006. :dontknow . That being said I purchased my servo gear seperately and not from Bergen.

For now...I'll try to get this set-up working. If it means upgrade then maybe I'll start looking for 611/9256 combo. :bawl

Is the 611/9256 combo recommended to be used with the push/pull upgrade?
Rob.

[rappy-60]

Is the 611/9256 combo recommended to be used with the push/pull upgrade?
Rob.


My understanding is no. Bergen does not recommend the push pull system for futaba servos. I have the 611/9256 combo and Im going to swap it out with my 50 which has a 401 in it. I think the 611 is overkill, but others here might have a different opinion.

Dale

[Helisin]

Finally got out yesterday and tweaked the EB in the hope of getting to the root of the tail kicks. Two things seemed to have helped...

1-Installed the stock T/R pitch change system with small futaba servo wheel. Limit pot on 401 is now just above 120 instead of 80-85. Set up with no drift in non HH. Ran it with no tail kicks but still had lexan canopy cheek vibrating away on one side. No tail vibes.

2-Finally got my optical tach so I tached the head speed at 1600ish. Adjusted throttle curve to bring it down and found a sweet spot @ 1530-1550. Thanks to Mark for taching. No vibes present. Seemed to be smooth as silk. Very nice. I don't think I need to adjust the needles as it is running smooth and crisp with no real bogs or mis-fires with spool up or climb out.

There is still a slight drift in the tail but I've yet to play with the sensitivity. Next time out I'll get to that. For now the main problem seems to be taken care of. :D :D

Rob.