Hello Buddy.

Sorry I keep reading your post and I'm wondering if you're refering to the use of the actual swashplate mix values, or are you refering to sub trim to level the servo arms at 90 degree's? I'm leaning towards sub trim ratehr than reducing your swashplate mix values to zero, or else the control's would not move.

I'll be back when you've clarrified for me.
.

Yeah sorry I'll go back in & correct it.

I think you have to as per manual set heli in DIR mode & if sub trim is used 3GX must store the settings so when you come out of DIR & then default sub trims, unplug & plug in heli 3GX remembers the DIR settings how else could it be.?
I would need to try it" so if I again setup heli in DIR & not put any sub trim in so swash is not quite level I think it will store like that so when you reconnect battery swash won't level...? sounds feasible but going to need to give it a go even if its just to satisfy my own thoughts.

I too am keen to hear the result of this. I have a slight rearwards drift all the time and can't seem to get rid of it. A friend of mine has just bought a 450 Pro v2 3gx too and he has exactly the same rearwards drift issue. I levelled my swash using a swash leveller in DIR mode and it's level from low stick all the way to high stick. I have sub trim set also.

Watching this post for sure. I had the some backwards drift but on take off was back and left. Since then I have changed TX so re done the whole setup procedure from scratch and it reacts exactly the same with the new TX. I have replaced swash bearings and main bearings as not so good so will hopefully get a chance to fly tomorrow. I am thinking there is some common mechanical problem that causes the problem. I would expect the 3gx units to be fairly consistent with there build and results so maybe something else is messing with them?

Need to try and understand what is actually happening to make the 3gx think the way it does. I assume it is measuring movement through the gyros to detect drift. Is there any way the 3gx knows it level? Has anyone tried running through DIR setup with tilt on the heli?

Maybe need to look at common mounting positions, Mounting pad number etc. Mine is on the top mount Trex 500 efl pro facing backwards so the plugs are at the front with both mounting pads that came fitted.

Here is an interesting little video to explain how a gyro works.

How It Works -The Vibrating Gyro- (Science And Stuff) - YouTube

interesting but was cut a bit short

I had a rearward drift issue on mine. I moved the 3gx to the bottom shelf (500EFL pro) and changed all my bearings and the drift has now disappeared.

Now this gets even more weird.!

I've gone back into DIR mode with sub trims all zeroed & with swash levelling tool in place then I went through the setup process both sticks centred I press set button though to the end to find no changes to my previous setup so then went back into DIR but this time I went mid stick then pressed button to go through cyclic & tilt setup this time I found when I came out of DIR the swash wasn't level so my previous theory was right 3GX does store the sub trim setup just like the Beastx does.
Now I need to test my tail drift theory once weather is good to be more sure as I only done one lipo after I zeroed sub trims so need to do some more test flights.
We now know 3GX does not default itself until you put in the elev limit in DIR mode but we are able to go in & double check the swash is level & come out of it without altering you previous setup providing you don't use cyclic input.

Hey All.

Ah, thought you were refering to sub trim, but wanted to be sure.

If my friend comes in here he will tell you that sub trim to me is a very, very bad word!
I hate using it, yes it's there to make setup easier, but I do feel it can actually make things go horribly wrong in an FBL setup. The 3G and 3GX is no exception to this and I have felt that if sub trim is used during DIR mode, or too much atleast, then the overall flight performance isn't as good as it could be. There are exceptions, such as the Vbar, where one adjusts the sub trim to put each control channel at it's absolute middle position. However the amounts needed to do this are very small, we're talking 1~4% max in most case's as we are not looking to level the servo horns, just the electronic positions.
Quite why problems creep in when sub trim is used I do not know, as you are advised to set any sub trims during DIR mode with the 3G/GX, which as you have seen, then gets stored into the 3GX's neutral position memory and all controls then move from this reference point. Hence the need to only adjust sub trim while in DIR mode, or all you are effectively doing is adding a movement command to the channel on which sub trim was altered.
There is a worry in that some transmitters did not allow for any shift in a channels neutral position, via the use of sub trim, by adjusting the overall travel limits to match. What would happen is say you shifted the sub strim 10% to the right, you'd then end up with 110% left travel and only 90% of right hand travel available. This has been fixed in recent years on the high end sets, I think Spektrum was one of the first to actually advertise their transmitters did this(?), but old sets may not. What this can mean is that if any sub trim is used then that channel will not mvoe through the same amount of control steps as the others and on an eCCPM type model, with 3 servo's moving the swashplate, if one moves less than the other two the swashplate will not stay level throughout it's travel. I cannot speak for the Beastx, but I know the 3G/GX does not allow the user to adjust the upper and lower swashplate points electronically through a PC based software interface, but the Vbar for example does. So if there is any mismatch in swashplate servo(s) movement it can be mixed out by trimming the servo's electronically.

On larger machine's it's very easy to setup servo horns level without the need to use sub trim, the Align servo wheels are great for this and with a little more patience during the bench setup you can keep rotating the wheels until the steel control balls line up. Having said this I have seen sub trim used to attempt to rectify a bad bench setup, in the pursuit of getting the job done quicker, but that's another story
On the smaller 450 machines, where we need to use single arm servo horns, lining them up get's much more difficult (if near impossible) at times. With my own 450 PRO/3G/GX I spent age's swapping and changing servo arm's between servo's until I came across a combination which meant I only had to add at worst case 5~10% sub trim. If memory serves correctly I managed to limit it to the elevator channel only, but it was a time consuming task.

For me the bottom line is to avoid sub trim at all costs with the 3G/GX and if you must use it, do so sparingly.
Re-reading your post it's got me think if the 3GX loads the sub trim in on startup, then part way through the flight looks at as a pilot stick command, which causes the drift/out of trim feeling? I say out of trim as any helicopter will naturally want to drift offline, as our the 3GX unit's do not have GPS hold functionality as yet and so will not attempt to hold a fixed position.

Ideally it would be great to replace the single servo arms with small wheels, which would allow us to position a control point at 90 degree's to the servo without using subtrim.

To perhaps prove a train of thought, how about getting the arms as level as you possibly can, then setting the swashplate level with the control rods. While it would not make for a perfect setup, if the model atleast hovers and does not start to drift we may further prove that sub trim is a cause of problems.
It might be even better to find the servo with the most out of position arm and make the other two match this one, so that the arc at which the control rod moves through is the same on all 3 servos. Again it's not a great setup, but to prove the theory.

Also, the travel limits on each servo should not be moved, it specifically says so. However some have made changes to the end points and not had any detrimental effects on flight performance. I've not done it msyelf and so cannot pass comment, so conduct any experiments at your own risk
.

I don't quite understand this. I seem to read it as both being the same procedure.
First one says sticks centred which would be midstick and zero pitch. Second says mid stick, which is the same as the first.
Could you confirm what you mean please.


Edit.
Read through a few times and think I understand a bit now. First time I take it just go into DIR, don't change anything just step through the status button.
Second time you move the sticks to do the DIR adjustments, ELim etc.
Hope you can confirm what to do.

Very interesting thread.
At least something good coming out of a dreadful day of weather.

Just begining to come to terms with v2 as only setup 500 yesterday, no flight tests yet.
On v1.2 I have tail dropping drift which gets worse through the flight. Similar problem on my friends 450 pro which also has side tilt drift together with tail drop and a 500 efl pro with tail drop.
Would love to see this sorted as otherwise I find the 3GX really good.

Good topic. Spent ages yesterday trying to minimise subtrim. As to gps on 3gx... Looks like it is on its way.
http://www.align.com.tw/disbb/viewth...extra=page%3D1

Looking interesting but where on earth are we going to find the space. I'll struggle on my 500, don't think on my 450, certainly not 250.

Seems to be an auto pilot system. Interesting for spying

Ian (coolice) when you mentioned in another post about adding sub trim to correct tail drift & I explain that I got to 80% elev & heli still had tail drift the reason is obvious now because 3GX doesn't except sub trim unless you go into DIR mode so it can save the setting, hopefully I will get to test the 450 tomorrow & the test will consist of flying with swash plate level with sub trim then zero sub trims & if do still have tail drift then I add elev sub trim & if as I suspect still have tail drift I will then go through DIR & add slightly more sub trim & go through the DIR save setting this im sure will fix the issue.

Although as you mention is not to good to have to much sub trim but its an easier way to test it out, once i know i zero sub trims & find a way of making the adjustment without sub trims.