Backward drift with 3GX

[ReadyToCrash]

to be fair, "tendencies" are not a 3gx feature only. i changed my 3gx for a beastx because of an insistent tilt the heli had when inverted, but found out the heli has the same problem with beastx.

[bad007]

Weight distribution.?

[thomas311]

Hi everyone, I'm new to this forum, but I spent a lot of time reading through it. In the past I was a bit more active on rcgroups. I encountered the sam back drift problem on both of my helps(TREX 550 #GX and TREX 450 3GX). I read about that issue on several threads and forums and I decided to spend some time with setting up both of my helis from scratch.
After flying both just 30minutes ago, I think I got the backwards drift fixed. Here is what I did:
1. Update 3GX to V1.2
2. Ran the whole mechanical setup procedure according to the manual for both helicopters again (DIR mode): swash plate leveling at center stick and so forth. Set pitch and cyclic according to manual (both according to stable flight setup, not 3D)
3. Connected my laptop again and loaded beginner settings on both helis (I consider myself still a beginner), then customized the beginner settings in the Bell-Hiller section and applied 50-70 (I read about that somewhere else - and the factory setup was way different on these two values)
4. Ran the electronically setup for endpoints of rudder.

Then I flew both and it was a bit windy (approx 7mph) :
for my 450 i can say at least it is way better (if there was no wind, I could be more precise), I dare to say it feels perfect.
for my 550 i can say that that baby stood still even in the light wind like a rock (nose in wind and tail in wind)

For now I'm happy and continue practicing.
Hope I could help some of you.
Cheers
Thomas

[bad007]

I too just tried something, with flybar paddle gauges on to set 0deg mid stick and rocking the blade to see what any loosness did in relasationship to the FBL gauge making sure with pressure under the leading edge the pitch was 0. as to favor forward motion. Also after rotating the blades 180, 90deg. to the boom the gauge revieled a slight pitch change indicating the swash was off a tad even tough the leveler showed it to be level. The elev servo horn got 2 bumps of sub trim down and then all was good. Next tail box alignment, it looks level, well why not tilt it just a tiny bit so there's a small downward force from the tail blades, ever so small you needed to use your imagination to see it. Went out poped my velo up about 6 feet and took my hands off the sticks and it just drifted ever so slow FORWORD! about 30 yards in 30 seconds and never even gave it any stick input. I figured on climbouts the tail drop would be better with the tail box tweeked also,,right? That slight downward force helps with the tail now. Flew great and it used to come to a stop and jet backwards before without continous forward cyclic.
Next it to go over the 450 pro

[Colorado_Scott]

Thomas, Bad.. good inputs. I am please with how my heli is flying. My largest change, is 2 fold; 1) I removed the primary Rx and am using the 3GX now with Sats. A large difference here is when I arm the system, before, using the AR9000 w/ satellite (an excellent Rx), my head would jump up and down 3 times (normal) but the head would end tilted 45 degrees to the left - most of the time. I'd remove the arming plug, and try again. Sometimes, 5-6 times before the system would initialize correctly. Now using the 3GX with sat's, every time it initializes perfect - swash level. 2) I changed out my swash with a much smoother one. This has made a large difference in hovering. I'm not sure I have backward drift at this point, where before I did for sure.

Not sure I'd ever take my hands off the stick, but perhaps someday I'll give that test a try. I will look to see if I can tilt my tail blades just a tad..

[koppterx]

you should not be afraid of taking your hands off the sticks. unless the heli is trimmed really bad or it did not initialize properly it will just sit for a couple of seconds before it shows any bias.

[thomas311]

Originally Posted by Colorado_Scott

Thomas, Bad.. good inputs. I am please with how my heli is flying. My largest change, is 2 fold; 1) I removed the primary Rx and am using the 3GX now with Sats. A large difference here is when I arm the system, before, using the AR9000 w/ satellite (an excellent Rx), my head would jump up and down 3 times (normal) but the head would end tilted 45 degrees to the left - most of the time. I'd remove the arming plug, and try again. Sometimes, 5-6 times before the system would initialize correctly. Now using the 3GX with sat's, every time it initializes perfect - swash level. 2) I changed out my swash with a much smoother one. This has made a large difference in hovering. I'm not sure I have backward drift at this point, where before I did for sure.

Not sure I'd ever take my hands off the stick, but perhaps someday I'll give that test a try. I will look to see if I can tilt my tail blades just a tad..

I had the same problem with my 550 3GX and the AR8000 incl. telemetry in it. Every other time it stayed tilted as you described. For me a rebinding between TX and RX solved the problem. My 550 initializes fine every time and I can use telemetry (not that I really need it - but it's fun). I p;lag to have this one in a scale fuselage with retracts and therefor I needed the AR8000 to work.

[espressonik]

Thought I'd get to the bottom of my 450 drifting backwards. So I started from scratch. Made sure the Swash was perfectly level and then when it was I checked it another 3 times from every angle to make sure. Then I went through the DIR setup, and followed all instructions in the 3GX program flawlessly. When I was happy, I took her out for a flight.
I had turned the dials up slightly on the 3GX unit (just past 12 o'clock on both) and I had replaced the stock standard align head dampeners as the head was a bit sloppy. Absolutely perfect! Flew like a dream. was able to take my thumbs off for about 4 seconds no worries when hovering. no drift at all.
Don't know if this will help all of you, but I hope it helps someone. yesterday I could have sworn it was my 3GX unit that was the problem, but I decided to eliminate all other possibilities first, and it paid off. good luck guys!

[bad007]

I can say my backwards drift is GONE! I mentioned earlier and now it is gone for sure and here's some pics. of ever so slightly tilted tail box and my method for leveling the blades and making sure the swash is level becides the conventional leveler
First level bades from one side, then rotate 180 and recheck, if the gauge is off after rotating the swash is off, mine was off, 2 points of sub trim and had to lower the elev horn. Also check from front to rear inline with the boom. I placed a boom brace on the gauge to aid in alignment.
With the 3G we automatically knew to lower the lock gains and if we had drift the gain was to low, I lowered the lock gains 5 and upped the gain comps 5, the pots at 1:30 and there's no drift at all, accelerates faster, hands off hover for a good 15 - 20 seconds and no drift in any certain direction period. Feels better than ever before.

Notice I tilted the tail box ever so slightly

Level both blades from the same side

Rotate 180 and make sure the gause is still on, if not the swash is off the direction is the gauge is tilted.

And here with two FB paddle gauges on to make sure both blades line up together.

[rc-bender]

I have the 3GX on two different helis (450 & 600) and half way through about 50% of my flights both develop a rear drift in a hover. Very odd, very inconsistant and definitely not mechanical or related to trim etc. They'll both hover hands off in the beginning of a flight and by the end the tail is dropping hard.

If I don't see a solution by summer when I'll start flying more I'll have to switch brands. They fly great normally, so this behavior is quite dissapointing.

[espressonik]

rc-bender, is it possible that tight wires could be pushing the 3gx unit up? or could there be fluctuations in power to the 3gx unit?

[bad007]

Originally Posted by rc-bender

I have the 3GX on two different helis (450 & 600) and half way through about 50% of my flights both develop a rear drift in a hover. Very odd, very inconsistant and definitely not mechanical or related to trim etc. They'll both hover hands off in the beginning of a flight and by the end the tail is dropping hard.

If I don't see a solution by summer when I'll start flying more I'll have to switch brands. They fly great normally, so this behavior is quite dissapointing.

That velo I pictured did the same, jetted backwards after awhile. It turned out to be a combination of things and is now gone. I had a swash that tilted as you gave it pitch. Fixed that and it still drifted. I tilted the tail box a minute bit, better but still had a slight drift, checked with flybar paddle gauges from both sides and it revealed I needed two sub trims down on the elev servo. On top of that I moved the controller closer to the main shaft and that let me fasten the wirring 3 inches away and before it was 2 inches, dropped the locks and raised the gain. No more drift. You can not believe it's the same helli when you fly it.
Next is my 450 Pro, it has a slight drift backwards and I just trimmed it and flew it.

[rc-bender]

Originally Posted by espressonik

rc-bender, is it possible that tight wires could be pushing the 3gx unit up? or could there be fluctuations in power to the 3gx unit?

The wiring on both helis have plenty of slack. The power should be good too. The 600 uses a dedicated 2s LiPo and the 450 has a castle BEC. Neither are powered off of the ESC.

Swash is level at mid stick, COG is spot on, and both helis hover wonderfully when the problem doesn't show up.

I don't have a link to it now, but I saw a video earlier of someone re-creating the problem on the bench. After several minutes of cyclic input on the bench the swash wouldn't level anymore.

[Sowa]

I have a brand new 3gx system and it started to drift after about 4 packs through it, could it be because i'm using two of the mounting pads?

[Gazey]

I've been following this thread for some time as I also have a backwards drift on my 550E V2.
I have noticed like most others it starts off fine and develops a backwards drift during a flight.
I plug in a lipo on a nice level surface and let the system initialize and note the swash is nice and square with the main shaft.
Pop up into a hover, no problem. Rock solid and stable.
Move into forward flight, do a few figure 8s and a few circles and start to notice I need to keep pushing the elevator forward more and more to keep it moving forward.
Come back into a hover and WTF it wants to drift backwards.
Land the heli and look at the swash and its lilted back quite a bit.

Just let the heli sit there, don't touch a thing and after about a minuet the swash slowly and deliberately moves back to level.
Has any one else noticed this happening....

This is definitely what's causing my backwards drift.
The way I see it it has to be software not the set up.

[bad007]

Originally Posted by Gazey

I've been following this thread for some time as I also have a backwards drift on my 550E V2.
I have noticed like most others it starts off fine and develops a backwards drift during a flight.
I plug in a lipo on a nice level surface and let the system initialize and note the swash is nice and square with the main shaft.
Pop up into a hover, no problem. Rock solid and stable.
Move into forward flight, do a few figure 8s and a few circles and start to notice I need to keep pushing the elevator forward more and more to keep it moving forward.
Come back into a hover and WTF it wants to drift backwards.
Land the heli and look at the swash and its lilted back quite a bit.

Just let the heli sit there, don't touch a thing and after about a minuet the swash slowly and deliberately moves back to level.
Has any one else noticed this happening....

This is definitely what's causing my backwards drift.
The way I see it it has to be software not the set up.

I've heard of that.
I monitored my bec volts on the bench working the pitch fast and constant and it dropped slowly and after awhile the 3GX glitched and even after no input it took about 30 seconds for the voltage to rerturn to normal. A CC Bec Pro fixed it. There's constant correction with FBL and if the bec isn't up to the task the voltage will eventually drop until there's amalfunction of some sorts. Mine glitched when the bec volts hit 5.2 volts and took a good 30sec to return to normal.

[Bigcal45]

Originally Posted by Gazey

I've been following this thread for some time as I also have a backwards drift on my 550E V2.
I have noticed like most others it starts off fine and develops a backwards drift during a flight.
I plug in a lipo on a nice level surface and let the system initialize and note the swash is nice and square with the main shaft.
Pop up into a hover, no problem. Rock solid and stable.
Move into forward flight, do a few figure 8s and a few circles and start to notice I need to keep pushing the elevator forward more and more to keep it moving forward.
Come back into a hover and WTF it wants to drift backwards.
Land the heli and look at the swash and its lilted back quite a bit.

Just let the heli sit there, don't touch a thing and after about a minuet the swash slowly and deliberately moves back to level.
Has any one else noticed this happening....

This is definitely what's causing my backwards drift.
The way I see it it has to be software not the set up.

That is what mine does everytime. Its not a mechanical setup problem, its the 3GX doing it. My BeastX should be here today, after months of fighting this I may have found a solution.

[Gazey]

Originally Posted by bad007

I've heard of that.
I monitored my bec volts on the bench working the pitch fast and constant and it dropped slowly and after awhile the 3GX glitched and even after no input it took about 30 seconds for the voltage to rerturn to normal. A CC Bec Pro fixed it. There's constant correction with FBL and if the bec isn't up to the task the voltage will eventually drop until there's amalfunction of some sorts. Mine glitched when the bec volts hit 5.2 volts and took a good 30sec to return to normal.

I am running a CC Bec PRO so voltage should be OK.

[Gazey]

Originally Posted by Bigcal45

That is what mine does everytime. Its not a mechanical setup problem, its the 3GX doing it. My BeastX should be here today, after months of fighting this I may have found a solution.

I am also waiting for a Spectrum AR7200BX to arrive to fix this problem

[Colorado_Scott]

Bad - good pix.. is the tail tilted to the left slightly ? Real hard to tell.

Please explain this a bit more..

I lowered the lock gains 5 and upped the gain comps 5, the pots at 1:30 and there's no drift at all, accelerates faster, hands off hover for a good 15 - 20 seconds and no drift in any certain direction period. Feels better than ever before.

I do not understand the above.
--------------------
OK, I own someone a drink!! I went through my head / blade alignment to as close as I can possibly see. I adjusted the Pitch from 17+ to 19+ and the Elevator from 4D to 2D. This gave me as close as I can measure to perfect zero pitch at each 90 of the blade rotation, all sides. I then checked my rudder / stab to 90 degrees to the blades, thinking if possible I'll rotate the V-fin a bit to the left. I found it fully to the right as much as it would go - which is close to 90. I then loosened the boom at the fuselage and found there is a lot of play, clockwise and counterclockwise.. and the screws were not 'real tight'.. so I rotated the Boom a bit to the left, tightened these screws very tight this time.. then I decided to check the tail sections.. crap, it was ready to fall off.. (not really, but loose w/o touching any screws - it would rotate the metal part right and left with little effort).. so I rotated a bit to the left again, and tightened securely. I am not positioned like BAD has his, in the posts 1 page back. I did not realize there was this much play in the tail section.

We got a good 12" of snow outside, so now I sit and wait.. but I'm sure I'll clear a section from the street and hover tomorrow to test this.

Thanks