MSH Brain + DX6i tail wag?

[madeye]

I'm just lifting the whole thing up for the first time, being really careful - hope this is just a silly novice problem...

How to reproduce:

- Default YGE setup
- MSH Brain setup with no governor (for now)
- DX6i gyro at 51% (the minimum which enables Heading Lock if the gain is not set in software - which is kinda surprising by itself, Brain configurator says it should be at about 45%)

Lifting up at x=y throttle curve, seeing about 20° tail wag upon liftoff.

Didn't want to risk 100% throttle yet, wonder if the wag could've just been caused by insufficient tail authority at low head speed?

Lowering gain is not an option, heading lock gets disabled. Mechanics seem to be fine, no binding.

[para5063]

What hole on the tail servo arm are you using? Hard wagging usually means too high mechanical gain.

[madeye]

Originally Posted by para5063

What hole on the tail servo arm are you using? Hard wagging usually means too high mechanical gain.

The one that gives the shortest arm.

Actually, the solution turned to be counterintuitive - *increase* the gain value in DX6, now it's good. I guess I need to read the docs on what they understand by gain there.

60-70% is where I tried it, both values are good (for my very limited flying skills).

[Russell Harding]

I think you were misinterpreting the term wag. For most of is it is a very fast chattery/bouncy tail by about ten degrees.

I think you were describing a soft tail kick, with the tail kicking right 20 degrees on liftoff and returning to center.

Tail kicks and blowout are from low gain. Wag and chatter are from high gain.

[PhxFlyer]

Hi, I ran into a bit of a tail wag issue today as well. I recently up'd the headspeed from 2900 to 3100..do you have to adjust the gyro gain in unison to match the additional speed? Mine was a pretty steady 10 degree back and forth chatter with it being more aggressive on u-turns or elevation changes...not un-flyable, but definitely not stable and locked in.

What's the decision tree to ID the cause and solution?

[thanasi]

Yes u would adjust gyro gain to each flight mode


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[madeye]

Originally Posted by Code3Medic

I think you were misinterpreting the term wag. For most of is it is a very fast chattery/bouncy tail by about ten degrees.

This is exactly what I'm experiencing. Less now that I got deeper into PID setup, but still there at higher headspeed.

Originally Posted by Code3Medic

I think you were describing a soft tail kick, with the tail kicking right 20 degrees on liftoff and returning to center.

Nope.

Originally Posted by Code3Medic

Tail kicks and blowout are from low gain. Wag and chatter are from high gain.

Yepp. Here's why:



That puzzled me too - I know PID theory well. Still need to read the fine manuals and figure out where the logic gets reversed, but the fact is still there - *raising* gyro gain to 60% got rid of oscillations (which were *very* obvious and unpleasant before that).

Just to be absolutely sure we're talking about the same thing - this is the value you access on DX6i with Option/Gyro path (page 115 in the manual), default value is 50%.

[Aryemis]

I think I am also experiencing something similar.
My tail is fine at 2800rpm, but when I push it at 2400rpm, it does a weird wagging thing, as if the gain was too high (except it's not obviously since it's tuned for 2800rpm).
Haven't tried upping the gain in 2400rpm mode yet, maybe I'll try that out today.

I'm also maybe thinking the gov gain (SK540 gov) is too high for 2400rpm and is messing with the tail.

[madeye]

Looks like at least my DX6i is behaving strange. Been setting up Stingray 500, again, was puzzled by inconsistency between what DX6i says and what TG-Multi says, wrote down the mapping - well, it looks like the value DX6i shows is about 28±0.875% more than what TG-Multi is reporting.

[Russell Harding]

You can calibrate the channels. Not 100% sure gyro is one of them, since there isn't an analog input for it...

A quick search should pull up the way to boot into calibration on the DX6i.

[madeye]

Originally Posted by Code3Medic

You can calibrate the channels. Not 100% sure gyro is one of them, since there isn't an analog input for it...

A quick search should pull up the way to boot into calibration on the DX6i.

Are you referring to page 115 of DX6i manual, or something else?

That page illustrates exactly what I mean - when DX6i value is set to 72.5, TG-Multi says it's 45, and so on until 85.5 to 59.

Let me throw one more bizarre fact into this equation - when I'm configuring AccuRC with their dongle and trainer cable, their calibration menu properly reflects gyro gain at 50%, and it looks more or less right at 75%, give or take travel adjustment. So, so far, MSH Brain is off, TG-Multi is off, AccuRC is not.

[Aryemis]

Originally Posted by madeye

Are you referring to page 115 of DX6i manual, or something else?

That page illustrates exactly what I mean - when DX6i value is set to 72.5, TG-Multi says it's 45, and so on until 85.5 to 59.

Let me throw one more bizarre fact into this equation - when I'm configuring AccuRC with their dongle and trainer cable, their calibration menu properly reflects gyro gain at 50%, and it looks more or less right at 75%, give or take travel adjustment. So, so far, MSH Brain is off, TG-Multi is off, AccuRC is not.

I've seen the same behaviour on my SK540, while using the DX6i.
A weird correlation between the DX6i values and the SK540 values.

I'm hoping the Taranis will fix that issue.

[Russell Harding]

Originally Posted by madeye

Are you referring to page 115 of DX6i manual, or something else?



That page illustrates exactly what I mean - when DX6i value is set to 72.5, TG-Multi says it's 45, and so on until 85.5 to 59.



Let me throw one more bizarre fact into this equation - when I'm configuring AccuRC with their dongle and trainer cable, their calibration menu properly reflects gyro gain at 50%, and it looks more or less right at 75%, give or take travel adjustment. So, so far, MSH Brain is off, TG-Multi is off, AccuRC is not.

The calibration I'm talking about isn't in the manual (gotta love Spektrum, 132 pages and they leave the 'secret' menus out). If I recall, turn on the power with Rud and Ail trim tabs pushed toward the center, and TH on. However, I'm pretty sure only the sticks can be calibrated.

Does it matter what the gyro channel's reading is? Don't you still simply adjust the value until the model is flying right?

[Aryemis]

Originally Posted by Code3Medic

The calibration I'm talking about isn't in the manual (gotta love Spektrum, 132 pages and they leave the 'secret' menus out). If I recall, turn on the power with Rud and Ail trim tabs pushed toward the center, and TH on. However, I'm pretty sure only the sticks can be calibrated.

Does it matter what the gyro channel's reading is? Don't you still simply adjust the value until the model is flying right?

Yep I confirm there is a secret menu like that, can't remember for sure how I got in but I needed to do it as one of my pots was off.
I'm pretty sure it only calibrates the sticks though.

Yeah sure it works but it's kinda annoying to have different values on the input and the output.

[madeye]

Originally Posted by Code3Medic

Does it matter what the gyro channel's reading is? Don't you still simply adjust the value until the model is flying right?

It doesn't matter as soon as you realize that the value on the screen has nothing to do with the actual, but to get to that point... you start questioning everything.

And, how come AccuRC recognizes the value correctly?

Anyway, I'm planning to retire Spektrum to just mCPX BL as soon as possible, so it won't matter anymore.