V120D02S Subtrim Issues

I have a V120D02S with a RX2636H-D Receiver and a Devo 8 radio, I seem to be having some subtrim issues.
The Devo 8 radio and the V120D02S we're not purchased at the same time, the radio had been previously purchased with a Walkera 450.
I've had a few flights on the V120D02S and it's been flying well, I figured it was time to have a go at it and get the best mechanical setup that I could (I.e. servo arms at 90 degrees at mid stick) I moved the server alarms to the closest position that could be obtained to 90 degrees try to do the fine-tuning with the sub trims, this seems to work fine until the radio is turned off, when the radio is turned back on and I bind with the V120D02S the servos go back to their true center and seem to completely ignore the sub trim values that have been input, I've tried multiple times and with different config files and encounter the same problem each and every time.
I have two other walkera RX2703H-D Receivers ( one is in a 450 and the other is in a 500 size ) that I use with this radio and in both cases the sub trim feature works fine.
I'm just wondering if anyone else has encountered this problem? and if so where you able to overcome it?

Hello Don B,

servo subtrimm on FBL for 90 degree like V120D02s is not allowed / possible where the FBL does all the TS mixing.

ELEV and AIL just sends the signal to the FBL for the roll rates to get.
It has no actual control for most FBL units (Align 3Gx may be the exception with CCPM120 transmitter mixing) for the actual servos.

3x servo subtrim is therefore only allowed for flybar / paddle helis where e.g CCPM 120 will actually control and mix each of the 3 servos in the transmitter individual.
There may be some very rare RX / FBL exceptions...


Good news:
For FBL you can (only) use servo subtrim for:
- pitch channel for zero / 0 degree pitch in stick middle position
+ max / min servo travel (scale +-) for max and min pitch adjustments (if the FBL does not allow these customization by itself)

That actually works and I did that with the Blade NanoCPX.


This was one of the reasons (besides 6 axis, Spektrumization tests) why the V120D02s Walkera RX2636H FBL unit got removed by me even the heli was not flown one time.
The older Walkera RX2622V-D FBL 3-axis unit (does not overcompensate on nick according to forums) will be the same on this topic.
It is the same with the Walkera MasterCP RX2637H-D. Not any FBL setup.


Better FBLs like Spartan Vortex Nano, MSH Micro uBrain (rescue), EZNov Neuron FBL (rescue), Tarot ZYX-s will actually allow you a full servo / detail setup like:
- 90 degree servo arm fine-tuning on all 3 servos
- zero pitch / 0 degree setting with all three servos (like servo pitch channel subtrim)
- swashplate leveling (front, back, left, right) if it can not be done 100% mechanically

Thomas

Thomas.Heiss wrote: Hello Don B,

servo subtrimm on FBL for 90 degree like V120D02s is not allowed / possible where the FBL does all the TS mixing.

ELEV and AIL just sends the signal to the FBL for the roll rates to get.
It has no actual control for most FBL units (Align 3Gx may be the exception with CCPM120 transmitter mixing) for the actual servos.

3x servo subtrim is therefore only allowed for flybar / paddle helis where e.g CCPM 120 will actually control and mix each of the 3 servos in the transmitter individual.
There may be some very rare RX / FBL exceptions...

Thomas

Hi Thomas

Thank you for the information,.
You may be right and it might be the case that the V120D02S with the RX2636H-D Receiver is not capable of sub trim adjustment, but I do know for sure that the combination of the Devo 8 with Walkera RX2703H-D Receiver does have this functionality.
My son has the V120D02 with the Devo 7, I'm fairly certain he's never tried the sub trim but next time he comes I'll play around with it and see if I'm able to set it on his system, I'm not certain why I never thought of this before but I guess that would be one way to know for sure or if I'm on a Fool's errand or not.

Thanks again, Don B

Doesn't the FBL unit interprete any servo subtrim values on AIL/ELEV channel just as normal gyro rate values, like when you move your stick. Of course with that you do not control the exact servo positions...

Subtrim on pitch anyway changes all 3 servos together (FBL mixing already on pitch), not the only one pitch servo.