Help with trex 250 - RC Groups
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Oct 23, 2017, 05:20 PM
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Help with trex 250


Trex 250 dfc. 10j radio turnigy servos stock motor and esc. Nano tech battery 3gx Mrs fbl controller.
I have verified servos are connected properly and only throttle is reversed per manual. Right and left controls are reversed as well as elevator.
Also when I give full elevator, swash also move to the right on both full up and down elevator. I am not sure what else to do even when I reverse the channels I still get the right tilt on elevator control.
So far I have made sure all servos are installed correctly and plugged into right slot for the 3gx mrs. Any help would be great. I do have another 3gx Mr. Lying around but don't know if it works as it was given to me used.
3gx unit is set for 250
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Oct 23, 2017, 05:56 PM
GREY.riddles::{used}? hmm
Flying Pitcher's Avatar
Did you disable radio mixing in your transmitter?(it's designed for flybar heli)
Should be setting: normal or 1servo or something similar
Oct 23, 2017, 05:56 PM
Registered User
H1 swash is slected. To clear up post when I give left control swash moves right and vice versa same with elevator control forward is backward
Also with elevator input swash dips right as well but has a delay in this action to the right. So full forward elevato input tilts swash back and then a secound later to the right
Oct 23, 2017, 05:59 PM
Cá bhfuil an linn snámha?
spykez's Avatar
First thought: Have you got your radio servo layout on H-1? Have you set it up exactly per manual?

Second thought: the 3GX MRS is a VERY fussy controller. It is virtually UNPROGRAMMABLE, so it expects the right and left cyclic servos plugged in the right ports, there is no wriggle room for that.

IN ADDITION: it expects servos to follow the convention of the align DS410 servos. The implication of this is If you use ANY OTHER servos, to make them work on the 3GX MRS you may have to mod them so they move in the correct direction with as the align stock servos in response to the signal. Reversing on the radio to try and fix this will not help as that only reverses the radio signal and not the signal from the FBL to the servos

Third thought: if you crashed, maybe one servo is malfunctioning out giving you weird swash plate movement.
Oct 23, 2017, 06:09 PM
Cá bhfuil an linn snámha?
spykez's Avatar
Quote:
Originally Posted by Gsx9522r
Trex 250 dfc. 10j radio turnigy servos stock motor and esc. Nano tech battery 3gx Mrs fbl controller.
I have verified servos are connected properly and only throttle is reversed per manual. Right and left controls are reversed as well as elevator.
Also when I give full elevator, swash also move to the right on both full up and down elevator. I am not sure what else to do even when I reverse the channels I still get the right tilt on elevator control.
So far I have made sure all servos are installed correctly and plugged into right slot for the 3gx mrs. Any help would be great. I do have another 3gx Mr. Lying around but don't know if it works as it was given to me used.
3gx unit is set for 250
I reread your post. If you have never successfully used these servos before, it's likely the direction issue I mentioned.
Oct 23, 2017, 06:13 PM
Cá bhfuil an linn snámha?
spykez's Avatar
How to Manually Reverse a Servo (3 min 58 sec)
Oct 23, 2017, 08:25 PM
Registered User
Thanks I'll try this. To test the theory could I plug in an extra servo I have from my 150x they are align. And if it travels the opposite way you are correct.. correct? Would this also explain the movement of the Aileron servo to the Right?
Oct 23, 2017, 08:38 PM
Cá bhfuil an linn snámha?
spykez's Avatar
Quote:
Originally Posted by Gsx9522r
Thanks I'll try this. To test the theory could I plug in an extra servo I have from my 150x they are align. And if it travels the opposite way you are correct.. correct? Would this also explain the movement of the Aileron servo to the Right?
My advice is to plug in the servos as they are, set up the radio as directed in the manual, and see which servo needs reversing (manually), based on the observed motion of the swash versus the expected.

Alternatively, if you have align 410 or 415's you may be able to observe their exact behaviour and correct your new servos (manually) accordingly.

Source : I have done this before.
Oct 24, 2017, 03:49 AM
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spykez's Avatar
Just to mention the other option if you don't want to use or perform surgery on the turnigy servos is just to get align ones with the aforementioned numbers or change the FBL, I guess. The annoying thing about changing the FBL is generally you want to keep the weight down.

But I guess you can strip down an sbus S-fhss receiver (maybe Orange has a suitable product) and use a micro brain or vortex.

Tell us how you get on!
Oct 29, 2017, 06:11 PM
Registered User
Thanks for the help. Have a trex 450 pro with align servos coming in. Going to use kst. In it so will try those out in the 250. I would love to change out the 3gx Mrs. But have such limited space to work with. I bought the 250 used a few years ago and it's just been sitting. May get it working and sell for a oxy 2 to go with the oxy 3 and trex 450 pro airwolf build
Nov 01, 2017, 09:38 AM
Excellence is Expected
MakMov's Avatar
Yeah, like mentioned probably set up issue. My DFC (super combo w 410s) was a bugger to set up and ended up using a laptop and the software to get it all right and does currently fly now. It should not matter what direction the servo travel is out of the box. You just need to reverse it accordingly. And yes the TX does need to be set to no swash mixing. That is all done in the 3GX. Forget what you know about setting up a regular flybar heli, completely different animal.
I set up all my FBL Copter X X3001 X3002 Kbar mini 3GX and XZYs via laptop. It is the easiest way to go. FWIW the 3GX is the hardest of them all to get right.
Otherwise, IIRC you have to change the direction in the 3GX control itself not the TX. Or maybe either or, I don't remember now, its been a while since I set up a FBL heli.
Last edited by MakMov; Nov 01, 2017 at 09:55 AM.
Nov 01, 2017, 11:56 AM
Registered User
It has a 3gx Mrs in it not really programble I do have a carrot zxy lying round I have checked how well it fits and only receiver I have is a 8ch full size fhss futaba
Nov 01, 2017, 11:57 AM
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Xzy
Nov 02, 2017, 05:42 AM
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spykez's Avatar
Quote:
Originally Posted by MakMov
Yeah, like mentioned probably set up issue. My DFC (super combo w 410s) was a bugger to set up and ended up using a laptop and the software to get it all right and does currently fly now. It should not matter what direction the servo travel is out of the box. You just need to reverse it accordingly. And yes the TX does need to be set to no swash mixing. That is all done in the 3GX. Forget what you know about setting up a regular flybar heli, completely different animal.
I set up all my FBL Copter X X3001 X3002 Kbar mini 3GX and XZYs via laptop. It is the easiest way to go. FWIW the 3GX is the hardest of them all to get right.
Otherwise, IIRC you have to change the direction in the 3GX control itself not the TX. Or maybe either or, I don't remember now, its been a while since I set up a FBL heli.
Mak, this thing unfortunately (eh, or fortunately, depending on how you look at it ) is a 3G X MRS. It's not like any of the 3GX preceding it.

From memory the only thing you can customise to some degree is the tail correction. It's otherwise like say, taking a blade 230S board and expecting to mod it to fly a 450. Completely possible. But takes a bit of work, well a bit more given the motorised tail, but you get the picture.
Nov 02, 2017, 05:43 AM
Cá bhfuil an linn snámha?
spykez's Avatar
Quote:
Originally Posted by Gsx9522r
It has a 3gx Mrs in it not really programble I do have a carrot zxy lying round I have checked how well it fits and only receiver I have is a 8ch full size fhss futaba
I don't know anything about the Tarot ZXY apart from some guys say it's quite decent.

The main issue with the 250 is keeping the bird light.

You may want to replace the casing of the gyro and the receiver to reduce mass and volume - careful, obviously many things can go wrong.

Also, I should add, if the gyro will not take S-BUS, I wouldn't even try it, it's just going to be a world of hurt with patch cabling.


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