Tail servo “sub trim”

When installing the tail servo horn, is it possible to get the tail servo horn to 90° in relation to the tail rod by adjusting the tail servo horn at the bench using the trim function in the AutoTrim menu?

you need to have it mechanically setup for 90 degrees, if that horn does not, try another till one fits 90.....
than adjust ball-links till blades have a couple degrees counter force of the rotation direction of the mains...
sub trim/altering is not a good thing... get it mechanically correct and the rest will fall in place
Birdman

Hi,

to adjust mechanically, do it with the model powered off. 90° at the servo, at the bell crank.
Powered on, the tail servo will show an offset.
Adjust the servo arm so it‘s closest to 90°, then do a trim flight to let the VBar find the sweet spot (which must not necessarily be what you think it is ).
If necessary, adjust the linkage again so the VBar finds the sweet spot as close to 90° as possible.
You can dial in auto trim values for tail, to adjust center (for setup), this is probably the answer to your question, so yes.

—Eddi

Born to fly ...
forced to work.

I am thinking of all the "conflicting" setup options.

Without electronic sub-trim on the tail servo, it is very challenging finding a servo arm that comes out 90° to the tail rod. If I follow the method of getting the tail servo arm to 90° with the power OFF, then there is no way to obtain even travels when adjusting the travels with the power ON. So, instead of 100/100 tail travels, I would end up with something like 120/80 tail travels. Also, as far as performing an AutoTrim flight, this is not easy to conduct, as it is challenging to experience a windless day at an open air flying field.

So, how about if I do the following at the bench:

1) Use a servo arm hole length that yields between 190 and 210 total travel i.e 100L/100R, 120L/80R, etc.

2) With power OFF, manually set the tail servo arm 90° to the tail rod.

3) Adjust the tail rod length to end up with around 2° to 3° tail blade pitch against main blade torque.

4) With power back ON, adjust the tail travels, and DO NOT WORRY about uneven 120L/80R travels.

5) Since it may be a while for the next windless day to perform an AutoTrim flight, just adjust the tail Trim manually at the bench to obtain 90° servo arm (and 2° to 3° tail blade pitch).

Do these steps sound good?

Long text ... all written here including images:

https://www.vstabi.info/en/node/842#tail

regards (EN) / Gruss (DE)

Rainer Vetter

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Hello Rainer,

I've seen that before. As helpful as it is, it also leads to more unanswered questions. For instance, any concerns about ending up with uneven travels like 120L/80R when following this method? If unable to perform an AutoTrim flight because of too much wind, is it OK to manually "AutoTrim" the tail servo arm to 90° until the "AutoTrim" flight can be performed?

If you end up with uneven values, you can adjust the length of the tail pushrod to even that out. I always play with servo horn length (shorter equals higher values) and pushrod length till I am as close as possible to 100/100. To my knowledge this gives best tail performance.
And afaik autotrim for tail can be performed in windy conditions, only the trimflight needs to be windless.



1 mal bearbeitet. Zuletzt am 28.06.2022 21:43 von Netzferatu.

I believe you may be confusing Optimizer flight (any wind conditions) with Trim flight (little to no wind).

I understand I can adjust the length of the rod to even out the left and right travels, but I believe the whole picture dictates (a) tail servo arm 90° to pushrod at neutral, (b) even left and right travels, and (c) sum of left and right travel between 180 and 240 or so. Step (a) is the most challenging as it is difficult to find a servo arm that is 90° to the pushrod WITHOUT subtrim like it’s normally done with the cyclic servos.

I don't think step a is really neccesary, as the optimizer flight for the tail dials that in. But if you want precisely 90° from the start, you have to use an adjustable servoarm. I have one my Specter tail and that is working also very well.

Those adjustable servo arms may be a good idea, but they are generally limited to 19mm and 20mm servo arm holes. I have not seen adjustable servo arms with shorter hole distances.

Then look again... ;-)

Hint: KSTMW-5008

Eddi E. aus G. Wrote:
-------------------------------------------------------
> Hi,
> You can dial in auto trim values for tail, to
> adjust center (for setup), this is probably the
> answer to your question, so yes.
>
> —Eddi

Hi Eddi
The problem is the auto trim values are not used while in setup mode, have had the question from a customer and I pointed him to this thread, only to realize that adjusting the auto trim on tail servo does nothing in setup.

Cheers

VControl, VBar on all.
TDR, TDR2, TDF, TDS and TDSF
Peter

Hi Peter,

well, best practice is, adjust the servo arm and linkage without power as best as possible (servo arm closest to center with 2-3° of tail pitch, all bell cranks at 90° then if possible, then adjust the limits in setup as equal as possible within sensible maximum tail pitch angles), _only_ then exit and (re-)adjust center auto trim.

Or just use auto trim in flight and let it straighten out things.

The (nicely put ) workbench perfectionist might find this irritating (but why?), and mainly ones who are fresh from other radios and still love all their trim levers and sub-sub-sub-settings

—Eddi

Born to fly ...
forced to work.



1 mal bearbeitet. Zuletzt am 01.09.2023 09:19 von Eddi E. aus G..