DX9 Centering issues due to sub-trim

[Alky6]

Edit: Update -- Problem Fixed!

I will try to explain in simplest terms. I also have a request into Horizon support regarding this issue.
I am noticing that on surfaces where sub-trim is used to get the servo arm in the correct orientation for geometry purposes, when changing travel adjust (whether in the servo menu or D/R) and expo adjustments, the centering of the servos (on any surface with sub-trim being used - it is worse the higher the subtrim) change as the travel adjust changes (or expo changes). If I set up different rates for different flight modes, the center point of the surfaces change. Pretty horrible for IMAC when you work really hard to get the plane trimmed out to have it change when the flight mode changes. How have you guys got around that, or is this just a problem with my radio?

I guess one way would be to use programmable servos to set the arm in the correct location (requiring no sub-trim in the radio), but unfortunately I already (a year ago) invested in savox 1270tg's which aren't programmable.

I am pretty frustrated at this point, any thoughts?
Thanks,
-Paul

 

[AKNick]

So when you change from D/R settings via switch (with subtrim input plugged into the radio prior) you can see the centering change on the control services?? sounds like a faulty radio to me... Does it do this on a different model?

 

[Alky6]

Yes, on different models. No mixing involved. You can dynamically move the travel adjust and hear and watch the servos move. The monitor function also shows them to move. Most notable when you have a high level of difference in D/R, say one switch is 40% to the other of 100% and the surface noticeably moves flipping the switch.

 

[AKNick]

huh. how much sub-trim? I always use a little as possible and make the mechanical linkage as close as reasonably possible before using any sub trim without having a programmable servo. I know that the little micros will go nuts if you use too much trim without adjusting the mechanical linkage first. Have you tried the transmitter self-test yet? I think the DX9 has that. I would give that a try, and maybe adjusting your sub trim down to almost nothing if you can do that. If that doesn't work, I'd send it back. Horizon has great product support from what I hear.

 

[wfield0455]

You haven't done something like set separate trims for each flight mode have you? If not separate flight mode trims, my first guess with centers shifting based on dual rate changes would be a transmitter calibration issue. Try the calibration function and see if that improves things.
I've done what you describe a 100 times and even with fairly large subtrims, and dual rate changes from 20% to 100% the centers never change.

Wayne

 

[Alky6]

You haven't done something like set separate trims for each flight mode have you? If not separate flight mode trims, my first guess with centers shifting based on dual rate changes would be a transmitter calibration issue. Try the calibration function and see if that improves things.
I've done what you describe a 100 times and even with fairly large subtrims, and dual rate changes from 20% to 100% the centers never change.

Wayne

Thanks! That helps. Will investigate the calibration.

Edit: no flight modes set yet. Virgin new model - no copying from others. Varified no mixes, no flight modes. At the very beginning stages of the radio set up on the 35% airframe.

 

[Alky6]

huh. how much sub-trim? I always use a little as possible and make the mechanical linkage as close as reasonably possible before using any sub trim without having a programmable servo. I know that the little micros will go nuts if you use too much trim without adjusting the mechanical linkage first. Have you tried the transmitter self-test yet? I think the DX9 has that. I would give that a try, and maybe adjusting your sub trim down to almost nothing if you can do that. If that doesn't work, I'd send it back. Horizon has great product support from what I hear.

Sub trims vary from 20-71 depending on the servo. Only using the subtrim to get the servo arms so they are perpendicular to the servo case and parallel to the hingeline. Doing this (and getting the control horn holes the same distance from the hingeline) I have no binding of the servos on the ailerons (2 servos per wing) throughout the travel. Not familiar with the transmitter self-test, but soon will be.
Thanks!

 

[Alky6]

You haven't done something like set separate trims for each flight mode have you? If not separate flight mode trims, my first guess with centers shifting based on dual rate changes would be a transmitter calibration issue. Try the calibration function and see if that improves things.
I've done what you describe a 100 times and even with fairly large subtrims, and dual rate changes from 20% to 100% the centers never change.

Wayne

Thank you Wayne! I believe the calibration has fixed the issue. The problem is not showing up in the monitor now (it was before). I will have to wait until later tonight to verify on a model! Thank you, thank you @wfield0455 !!!

 

[AKNick]

AH calibration test not self test. Glad to see that fixed it. I knew it was something along those lines.

 

[Alky6]

Thanks @AKNick and @wfield0455 for your responses. The calibration did in fact resolve the problem. I verified on with servos plugged into the reciever. WOOOHOOOO!!

Thanks again!