Weird problem: Tail moving left during pitch-up

[RunarS]

Hello!
I have a weird problem with my T-Rex 500 with BeastX v 3.0.8, and I`ve tried the BeastX forum without getting a clear answer...
Since I upgraded from v 2, my tail now moves to the left (CW) during pitch-up. At hard pitch-up´s, the tail moves approx. 90 deg left, opposite of the behaviour of a tail not holding... It looks like the gyro overcompensates. (When the battery is low on juice at the end of the flight, the tail does not overcompensates quite as much.)
I`ve done the setup a few times, checked the tail dynamics, and all seemes normal (as it did on v2). I`ve tried to apply reverse revomix (parameter menu), but it does not manage to correct the problem. Tail heading hold is low (also tried very low), and the gyro gain is around 75-80% on my DX7 (lights at G on unit).
Any tips on how to correct this?
At idle-up 1 and 2, only the pitch channel moves on the transmitter servo monitor, as it should. Rudder is not moving. There is no revomix, subtrim or ruddertrim active in transmitter. I did a complete reset on the BeastX unit, and did a fresh, new setup. Still...this is what I get:

Any ideas?

[dunkonu23]

Runar,

That's a strange one for sure. It would appear the gyro is over compensating. For what reason, we need to discover.

1.. Are you running a governor? If so, disable it. If the tail still does the same thing, leave it disabled for testing.

2. Mechanics... Does your T-Rex have a torque tube (it sounds like it does)? If not make sure the belt is properly twisted such that the leading edge of the blades rotates up into the down wash of the main blades. Also make sure the blades have leading edge control. Lastly for this item, make sure the blades are installed so the leading edge of the blade goes into the main blade downwash.

3. I don't mean to be rude and please don't take this as such, but are you sure this is not you providing unintended rudder?

4. Is your microbeast placed per the manual? Flat or on its side perpendicular to the main shaft?

5. Are you absolutely certain the gyro is in heading hold mode--blue light after initializing?

6 Is your tail servo behaving normally when you move the tail manually--applying tail rotor pitch against the direction of tail movement?

This is definitely an odd one.

Scott

[RunarS]

1. Not running governor. Straight curves in idle up.
2. My T-Rex got a belt. Properly twisted, leading edge controll.
3. I´m almost 100% positive that I don´t apply rudder while pitching. It was the first thing I suspected, so I checked that one. To be absolute shure, I can tryt setting rudder expo to 60%, just to make shure there is no such factors involved during testing.
4. Yes, mounted sideways on the frame, perpendicular to the main shaft. Firmly mounted.
5. Heading hold, yes! Blue light.
6. Yes, tail servo behaves normal. No gain issue, I think. The tail holds well in backward flight.

Is there perhaps some bad bearings in tail that may "lock" during high motor torque? I´ve tried revo-mix in parameter menu, but that doesn´t correct the issue either...

[Azalin]

Are you using the stock foam from BX? If so replacing it with a thin double sided tape might solve your problem.

Also try to lower rudder ATV value on your TX's Travel Adjust menu.

Edit: Ignore my last sentence. I missed that you worked with the gyro gain.

[ahahn]

Here is an off-the-wall possibility.

Do you have "revo" mix turned on somewhere in your setup--either in the BeastX or even in your transmitter?

Specifically is it on and "backwards"?

[RunarS]

I do use the stock foam, but the unit is zip tied really firm to the side of the frame and is rock solid! No issues with v2, I noticed the change with v3.0.8...
No revo mix. I've checked. I also tried applying both normal and reversed revo mix on BeastX, no significant change.

[dunkonu23]

This is a good one.

Can you try three things:

1. Adjust stick tension in the rudder direction?
2. Reload v3.08.
3. Take Azalin's suggestion: Try using some 3m tape. 4010 or 4011.

Other than that, wow...

Scott

[360Wings]

Originally Posted by ahahn

Here is an off-the-wall possibility.

Do you have "revo" mix turned on somewhere in your setup--either in the BeastX or even in your transmitter?

Specifically is it on and "backwards"?

+1. that was my first thought too.. Make sure Revomix is turned off and see how it goes..

[nwmtech]

Agree with others. Turn RevoMixing off. Go back through the tail section of the Tuning Guide I wrote. I've made some recent changes and have gotten the tail much better on all my helis with it.

[dunkonu23]

+1 on the tuning guide!

Also you may want to try a simple rebind--it fixed another perplexing problem in this forum.

Scott

[ryem3]

Have you tried increasing the gyro gain until you get a tail wag? Seems like it is overcompensating, but it just might not be holding.

[sutty]

But it goes the other way, which personally I have never seen. How could this need more gain?

[cristian84]

i have the same problem!