450 Swash plate 0 pitch setup on Trex 450 Plus DFC RTF (3GX MR)

pvolcko

Well-Known Member
There is nothing in Tx setup you can do about this problem (well, almost, see below). On flybar setups you could do what Tony said and modify your elevator channel travel settings to get it level at top and bottom collective. However with FBL, since it does all mixing internally and collective travels are driven entirely by a single channel (pitch). Adjusting elevator channel travel will do nothing but impact your cyclic behavior (adjust the forward/backward roll rate for a given cyclic up/down stick position). If the FBL controller does not offer you a way to adjust elevator servo endpoints at min and max pitch, there is nothing you can do aside from finding a mechanical solution.

It is pulling a little extra at minimum pitch and pushing a little extra at maximum pitch. So adjusting link lengths will not be able to correct it. You are already at the inner hole on that servo arm (ELE servo), so that won't help either. You could try moving the two other servo arm balls (PIT and AIL servos) to the outer servo arm hole. This will make those two links push and pull a little more at the extremes of collective, making the swash a little bit closer to level at those positions. Given the amount of difference, I doubt it will completely close the gap, but it will improve it a bit.

Also, this gap is going to induce a forward/backward roll as you use max or min collective. The FBL controller will sense this and attempt to correct it, keeping it level through the climb as best it can. As a result, it is entirely possible that in flight you will not even notice it. If you do, you can setup a Tx mix (if your Tx supports it) to counter it. This mix can't really be setup on the bench though. I'd do it during a few test flights, little by little. And I'd test forward flight while using collective to climb and drop altitude, making sure the mix wasn't causing it to nose up/down unexpectedly.

Also, I learned it as anti-rotation bracket, not auto-rotation bracket. It keeps the lower swash from rotating out of alignment (it does this along with the mainshaft itself, which is the second point needed to brace it).
 
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Tony

Staff member
Actually on the original 3GX, you can adjust just the elevator. But not on the MR or MRS.
 

pvolcko

Well-Known Member
Cool. 7200BX and Ikon both do not have an option for making that kind of adjustment, only for zero pitch subtrimming.
 

Tony

Staff member
That is correct. I know for a fact that the 7200bx is done on a 1 servo 90º swash, not sure on the Ikon. But with the original 3GX, it's setup on a 120º 3 servo swash. Gotta love when they go mixing things up lmao.
 

Erfan

Member
So whats the verdict guys? :)
Should I just go with the 0 pitch at mid stick and try flying and hoping for the best? :)

I thought to try pvolcko suggestion as well, moving the balls on the PIT and AIL servo arms. Will let you guys know how that went.
I will also try to send an email to Align and ask them how they did the perfect setup when it came from the factory, I'm sure there is a way, just need to figure out the right steps!
 

Sparse

Member
I went to the hobby store and really could not get to much info on the mr from what i did find out they are a very dumbed down 3gx meaning you can only do so much with them as far as set up goes. if i were you I would throw a set of training gears on it in case it wants to do something stupid on spool up you will be some what protected.

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and to be honest I watched you video and you servo arms did not look 90. has to be something your missing as far as the set up with that goes. it is a matter of finding out what it is.
 

Erfan

Member
I went to the hobby store and really could not get to much info on the mr from what i did find out they are a very dumbed down 3gx meaning you can only do so much with them as far as set up goes. if i were you I would throw a set of training gears on it in case it wants to do something stupid on spool up you will be some what protected.

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and to be honest I watched you video and you servo arms did not look 90. has to be something your missing as far as the set up with that goes. it is a matter of finding out what it is.

Hmm, maybe you are right but I have done everything I know to make sure that the arms are 90, I used a level tool and all 3 seems to be level, the ELE servo is a bit harder to check then the rest since its inside the heli but even that one should be 90.
I will try to check them all again, perhaps they are off with couple of degrees.

I have tried even what pvolcko suggested, that is moving PIT and AIL servos to the outer arm holes, that helped a bit actually, the gaps are smaller know but there is still gaps at both low and high stick.
I will try to email Align as well and see what they say...
 

Erfan

Member
Hi guys!

First of all, thank you all for all your time and help! :)
Second, I think I have finally found the answer, I bought John Salts Swash Level e-book for 10$ and the answer was in there, it seems that electronic stabilization systems only require perfect level at mid stick and then they will do it auto for low and high.
And travel adjustments must be exactly 100%, I guess that's what the manual was trying to say. I also found similar knowledge in another tread in another forum, also I think somebody said that this could happen in this thread so now its definitely confirmed.

Anyway, I will try to get everything together today or perhaps tomorrow and I will update this thread if everything went well but I'm positive that it will now that I have it confirmed from several sources.

Thx for everything so far guys!
 

Sparse

Member
John Salt writes very very good E-books, I bought one for my father in law because i gave him my 120 sr after I got my 450.
 

Erfan

Member
Actually happy to say that everything worked out just fine.

I have just been out hovering and its as stable as it was when I got it the first time.
After a lot of research it seems that the 3GX-MR version is really "smart", you only need to set:

1. Make sure all rods are set (length) as the manual specifies.
2. Make sure all servos are level to the swash (90 degrees against the main shaft).
3. Then check and adjust level swash at mid stick.
4. Make sure tail servo is correct as well (90 degrees against Rudder control screw)

That's it, the 3GX-MR will then make sure its level at low and high stick position when its up and running.


Thank you all for all you help!
 

Tony

Staff member
Hey Erfan, I'm happy to hear that everything is going well. Now all we need is some video of it in the air!!! :biggrin1:
 

Prloco510

New Member
To Erfan and all other members who have tried so hard to help him, thanks so much for the help because of his post and your answers I also managed to finally get the answer for my problem. I have the same model heli and what I thought was a problem leveling swashplate thru out negative and full positive range. This post has really saved me some headaches. Thank you all.
 
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