violent tail wag

[boosst]

i had a buddy here help me setup my DX7 and 600 n pro. i have now ran 4 full tanks through really rich. ever so often in hover the thing will start violently shaking and i have to set it down fast. i don't even spool down and lift off again and it is fine for another couple of minutes. is this a gyro gain problem or a vibration? i don't know exactly what all he set but said he had some more tuning to do after breakin. just curious..thanks

[Bobbyk]

You will need to give the freaks more info on the setup you have?

I will start by double checking the engine mounts, head (blade grips, thrust bearing, pitch, blade tracking, flybar and head speed), tail (TT, TT bearing offset center, thrust bearing, end play, gyro gain and where gyro mounted), how rich are you running your engine (os hyper - one and half for running it in).

The list could go on and on but give us some more spec of your beast and I'm sure one of the good freaks will help you out.

Robert

[Mercuriell]

Doesn't sound good - needs lookin into - it's not gyro gain problem. Go over the heli real carefully checking for any linkage binding and check security of all control link bolts. Also check the gyro mounting for security

[skyfreak73]

ever so often in hover the thing will start violently shaking and i have to set it down fast.

Do you only notice the tail shaking when this happens or the entire model?

[boosst]

it is an OS hyper. running about 1.5 turns out. the whole heli shakes but it is a back and forth motion. my g770 gyro was mounted on a very thin piece of double sided tape and not padded. i changed that out hoping that i might take care of it. if not, i don't even know where to start.

[aussiemick]

Sounds like the Head Speed is too low or Head dampenes are too stiff and you are getting a bobbing of the tail (up and down).
Either bump up your throttle curve or install softer dampners, preferably bump the HS up.

Mick

[boosst]

i used the softer head dampners when it was put together. i am not sure what the headspeed is yet...i will find out this weekend. the tail is going side to side, not up and down of that matters. it starts out just getting a little jerky and by the time i get it to the ground, the whole thing is bucking around pretty good. hopefully i can hover anohter tank in the next day or so and see if my new gyro padding has helped. thanks for the help. keep the ideas coming.

[stevehonn]

One thing to note with the 770 gyro is that it runs much lower gain settings than comparable Futaba gyros otherwise you will get violent tail wagging. I started off on 70% gain with the 770 on my 600N, same as I would start with a Futaba 401 gyro and the wagging was evil, I ended up around 28% gain to stop it and have since been able to increase gain to around 35% after fitting a Quick UK tail upgrade.

This may not be the cause but could be a contributing factor.

[aussiemick]

I use a logictech 6100T and have the gain at 39% in Normal and 33% in IU2.
I came from a TRex450 with the 401 and it was a bit hard getting my head around much lower gain values, but the tail at the lower gain settings has a stronger grip than the Boston strangler.

Mick

[maaatvee]

Also check that your tail linkage rod (that runs under the boom) is silky smooth and that the Tail Rotor Control Arm is also smooth and not sticking.

I was missing a washer on the bearing of the tail control arm that was causing it to stick which caused violent tail wagging as the tail servo fought to keep the tail from drifting.

anyways good luck eh!

cheers Mat

[boosst]

i think i found the problem. i had a guy help me set it up an another guy look at it today. it was initially set up at about 62% gain and we ended up lowering it to %32 and now it seems much better. my only question is why did it wait until every 2 or3 minutes to do this instead of right off the bat? thanks for all the help.

[biohazrd]

If are using the gyro sense value of 32% you are flying with that gyro in normal/rate mode. I am going to guess you are talking in terms of ATV gain. They are 2 different things. An ATV gain of 62=81% gain in gyro sense (very high) and most likely would cause series wags. An ATV gain of 32=66% in gyro sense (close to the recommended starting point of 62%).

If you are indeed using gyro sense figures and not ATV, then a setting of 32 is flying in normal/rate mode and your wag may have stopped for that reason alone. Sometimes a wag will occur in one HH but not normal/rate or visa versa.

I have only burned one tank on hovering with mine and it is not completely setup, but I heae the 770 likes a near perfect mechanical setup in normal/rate mode. Mine was close, only had a slight nose turn in normal mode, but it held fine in HH.

As far as the randomness of your problem it was probably tied to vibration that started at a certain headspeed/pitch movement. To much gain will make the tail more likely to have a fit trying to counteract false readings due to random harmonic vibrations.