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Pre built gremlin twitchy yaw

#1
Working with a pre built gremlin (Andres frame). It arrived last week and I have been setting it up over last two days. As far as I can tell I have setup everything on my end correctly. My issue comes with how it handles in flight. While in flight, the quad twitches on the yaw axis (at least that's what it appears to do). I'm new to PID tuning, but from what I understand changing the 'P' value for yaw should correct the twitch. No amount of value adjustments seems to affect the performance. The issue pops up in all 3 modes.

Anyone have any thoughts?
 

Snarls

Gravity Tester
Mentor
#2
Hi Snooch welcome to the forum! First off, is the twitch constant or does it appear intermittently and in certain conditions? Is the twitch one direction or both?

Besides PIDs, some things I would check are the camera and radio. Assuming you see the twitching flying FPV, look at the camera mount and see if it is loose and allows the camera some movement. If you see the twitching flying line of sight then it is not the camera. Second check your radios yaw channel. Connect to cleanflight/betaflight on your computer and connect the gremlin with your radio powered on as well. Check the receiver tab and see if the yaw channel shows a constant value of 1500. If it is moving around then your radio is causing the twitching.
 
#3
Snarls

Thanks for the welcome!

It's a constant twitch that moves back and forth. Almost like it moves between two positions. . I see it flying line of sight. I can have it in a hover and it just twitches left and right.

I'll try those tips tomorrow. Thanks for the advice.

Snooch
 

PsyBorg

Wake up! Time to fly!
#4
Welcome to Flite Test mate.

Two things I would check are looking at the receiver tab and watch how much your channels are fluctuating. If they bounce more then + - 2 points I would guess your potentiates are starting to wear and you may have to set a higher dead band. The other thing happened to me on a build where the JST servo connector for the receiver was not making good contact on my Alien when I maidened it. I ended up hard wiring that and it stopped immediately.
 
#5
Thanks for he suggestion.

Looked in the receiver tab and all my values are solid.

I still need to look at the physical connection.

Would reflashing the FC be a wise move?


Thanks
Snooch
 

PsyBorg

Wake up! Time to fly!
#6
Couldnt hurt. That has cured its fair share of issues.... Caused a few as well but ya rolls the dice ya takes yer chances.
 
#7
This is interesting. I chose to swap out my board for a pre-wired one (all that was available at the time) and all 4 of my ESC's after one stopped responding. The old board didn't fly long enough to spot this problem, but my new one does almost the exact same thing. Only difference is it "tick's" steadily CCW. Maybe about a second and a half, it just rotates left a few degrees. I was going to check PID's and see what the board is showing when running in Betaflight, but I'm willing to put money on it not doing it when the props are off. Was wondering if the black box feature could be used, and what exactly it would do for me in this case.

Any thoughts?
 

PsyBorg

Wake up! Time to fly!
#8
Its common on the femto. Mine did it lots.. I use 2 layers of the 3m double sided tape. The grey rubbery stuff with the red backing.

Between that, lowering yaw p , and upping min tbrottle I dont recall it happening since.
 
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#9
Its common on the femto. Mine did it lots.. I use 2 layers of the 3m double sided tape. The grey rubbery stuff with the red backing.

Between that, lowering yaw p , and upping min tbrottle I dont recall it happening since.
Thanks, I'll try that for a starters. That's the same tape I used with the first board (one layer had lots of vibrations, so I rolled it and used 2 of them to iso-mount it - worked much better). I'm using a the thick tape that was in the Bixler carbon kit now, and was wondering if I need to do the rolled tape thing again.
 

PsyBorg

Wake up! Time to fly!
#10
Yeah mate roll with the 3m tape. Foam tape actually conducts the frame resonance because it moves.

The tape is dense enough to absorb and does not move.

Be aware of anything touching the frame.. fc to esc wires, vtx wires, all of that. Make sure its secured well so it cant bounce and tap the frame.

With such a short wheel base the slightest tap produces big reactions.

Make sure camera cant tap the frame as well.
 

T-Richard

Active member
#11
Agree with double sides tape comments. I have a few femto boards and nothing from the frame can touch the board or I get the same yaw twitch you described. Flexi wiring and lots of double sides tape helps for me