Not as much negative pitch as positive?

[3din]

I'm setting up my flybarless 3gx 550e. I have set all the servo horns as close to 90 as possible but I still have to use subtrim to get them dead on. Something I've noticed is that I can get 18 degrees of positive pitch and only 15 degrees of negative pitch. I'm sure this is directly correlated with the subtrim I used to get 90 degrees on the horns. I've heard that you are NOT supposed to use end point adjustments with a FBL setup so how am I supposed to get them to move exactly the same amount positive as negative so I can tame it down in the swash mix percentage menu to 11 or so?

[jcflyer]

Ideally you want 12 deg. _ + on your pitch and around 9-10 on cyclic. Start at the bottom of the head and work your way up, bottom line is you need to have 0 pitch at mid stick and then your pitch numbers + and - should match or be really close.

[1004ron]

Isn't this the same thing:
https://www.helifreak.com/showthread.php?t=391808

[3din]

How do I work my way up from the bottom? I do have a perfect 0 pitch at mid stick but have more pos travel than negative

[jcflyer]

Your swash is not in the center of travel, you need to adjust the links from the servos to the swash to get it centered to have matching pitch ranges.

[bad007]

leighen the rods to the grips one turn and then lower the swash will you get your 0 deg. at mid stick with sub trim

[bad007]

BTW did you check from both sides?

[1004ron]

Originally Posted by 1004ron

With mid stick signal, servo horns at 90deg, swash level, ....... is the swash mix arms 100% horizontal, if not, you need to adjust the length of the servo to swash linkage rods - remember that the link rod lengths in the manual are ballpark figures.


BTW, its best to stick to one thread, and that way all will have some idea of what you have tried and other background info.

Originally Posted by 3din

That's probably it ... At 90 degree I horn and mid stick I doubt the swag mix arms are level. I'll try that thanks!!!

........................

[3din]

Sorry I know I have two threads covering similar topics but once I find the answer hopefully one will fizzle out.

I shortened the rods from servo to swash two full turns and lengthend the rods from swash to grips. Now I have the servo arms completely 90 degrees all three. swash mixing arm is now level, and I have 0 pitch exactly. I still have the same problem though. Here is the reason.

Lets say servo connection point is A, Swash plate is B, Blade grips are C. All I did is make change the center piece to be level... B.... The distance from A to C which is the main problem still remains...

I can visually eyeball the servo arms moving and they visually move farther up (positive pitch) than down (negative pitch). Does the fact that the arms all sat slightly on the high side and I had to subtrim them down to get a level 90 have anything to do with this?

HELP!

[1004ron]

Make 100% certain that there's no trim, hover-trim, ATV's at 100, and the pitch curve is 0 25 50 75 100


Edit: Deleted the word "subtrim".

[3din]

There is subtrim.... there has to be. I'm at 20 clicks or so for all 3 servos to get it at 90.

[bad007]

Originally Posted by 3din

Sorry I know I have two threads covering similar topics but once I find the answer hopefully one will fizzle out.

I shortened the rods from servo to swash two full turns and lengthend the rods from swash to grips. Now I have the servo arms completely 90 degrees all three. swash mixing arm is now level, and I have 0 pitch exactly. I still have the same problem though. Here is the reason.

Lets say servo connection point is A, Swash plate is B, Blade grips are C. All I did is make change the center piece to be level... B.... The distance from A to C which is the main problem still remains...

I can visually eyeball the servo arms moving and they visually move farther up (positive pitch) than down (negative pitch). Does the fact that the arms all sat slightly on the high side and I had to subtrim them down to get a level 90 have anything to do with this?

HELP!

Refer to my post, your horns aren't at a perfect 90, there high. The angle of the horns change expotentialy meaning the farther they move the more change there is so even a couple of sub trims make a huge difference at full travel. The cure is simple, more pos means the horns are a tad high so you make the long rods longer and lower the swash with sub trim the same for all three until your 0 deg. is back

[1004ron]

Originally Posted by 1004ron

With mid stick signal, servo horns at 90deg, swash level, ....... is the swash mix arms 100% horizontal, if not, you need to adjust the length of the servo to swash linkage rods - remember that the link rod lengths in the manual are ballpark figures.

Originally Posted by 3din

I can visually eyeball the servo arms moving and they visually move farther up (positive pitch) than down (negative pitch). Does the fact that the arms all sat slightly on the high side and I had to subtrim them down to get a level 90 have anything to do with this?

Originally Posted by bad007

Refer to my post, your horns aren't at a perfect 90, there high. The angle of the horns change expotentialy meaning the farther they move the more change there is so even a couple of sub trims make a huge difference at full travel. The cure is simple, more pos means the horns are a tad high so you make the long rods longer and lower the swash with sub trim the same for all three until your 0 deg. is back

Looks like you need to go back to the starting point, and that is to get the servo horns at 90deg. Try the horns on each of the three servos and see if where they pan out best with no subtrim, and then with just a little subtrim start getting them at 90deg, then swash level, ........

[3din]

So don't use the single horn arm that they suggest? Use the 4 arm one?

[3din]

Originally Posted by bad007

Refer to my post, your horns aren't at a perfect 90, there high. The angle of the horns change expotentialy meaning the farther they move the more change there is so even a couple of sub trims make a huge difference at full travel. The cure is simple, more pos means the horns are a tad high so you make the long rods longer and lower the swash with sub trim the same for all three until your 0 deg. is back

I think you meant to say the opposite... the servoe horns were high to begin with so I had to lower them with subtrim...


If I SHORTENED the main linkages I would have to add up subtrim on all the servos which would bring me closer to 0 subtrim....

EDIT You are right Im going to have to try this tomorrow

[chrismechanic]

i have not setup the 3gx but in beastx setup you 90 the servo arms in setup, adjust links to give 0 pitch, then teach it -/+ pitch values...no need to subtrim before setup at all ?
is the 3gx the same?
chris

[3din]

I don't think this is right because I know people are using subtrim to get it to work. I highly doubt all of you out there have no subtrim. This is really weird...

[Hoosiermo1]

I think you need someone with a 3gx to chime in. I use beast x and the subtrim is in the setup not the tx. I don't know if 3gx is the same. I would imagine somewhere in the setup there is a reference position and a "trim" setting for the servos. Without touching the tx.

[jcflyer]

Do it like this, start from scratch. Take your servo arms off the servos make sure all trims are centered and at 0. Now set your TX to mid stick, now put your servo arms back on as close to 90 as possible; now use subtrim to get them perfectly at 90.

[3din]

I don't think there is though....

Would I be correct to say if you use subtrim you will be limited in that direction (total throw)? If so this makes sense because I had to give the 3 servos beween 10-15 clicks of down subtrim and down (neg pitch) is where I don't get enough throw.

The only way I can see how to fix this if this is the issue is to use the 4 horn star to try and get as close to 90 degrees pitch as possible. I still think that you would need a tiny bit of subtrim to get them all perfect though (so that throws that theory out the window)....

It seems the only solution would be to limit the top endpoints or extend the bottom endpoints. Both of these solutions are clearly outlined in the manual NOT to do with the 3gx....

Sigh.....