General Tail shudders when using the rudder stick - after removing training wheels

[mooserider]

Hey all! I've took a couple week break recently because I had the worse flu of my life... almost two weeks in bed, it was brutal. The whole time I was dying to get outside and practice some more with the new helicopter.

I have had the 'training sticks' (not sure what you call them) on and have been practicing hovering and a little flying. It behaves really well, thanks to all of the help I got here. But tonight I wanted to take the sticks off and practice. When I did, the behavior of the rudder changed a bit. Now when I move the rudder and stop, it will shake back and forth quite a bit. I'm guessing it's the gyro having some kind of feedback loop, trying to correct itself. It stops after just a second or less, but it's really unnerving looking! I'm just not sure where to start with fixing that.

With the training sticks on it (they have ping pong balls glued to the ends), I don't see this happen at all when using the rudder. The sticks will occasionally cause a similar shudder when just hovering (no rudder input input), but only when they sort of resonate at the right vibration... then the tail gyro gets a little feedback thing going on, but it's only because it's 'fighting' the sticks' vibration. Otherwise it's solid with the stick on.

If you have any suggestions, I would love to hear them!

Thanks!
Moose

 

[Lillyryan]

Sounds like you need to turn the gain down a bit on the rudder. What Gyro are you using?



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[Lee]

Think of the training gear like to long pole a tightrope walker uses for balance.
It gives him stability.
Take away the pole an he will be flailing his arms around to keep his balance

Transfer this the the heli.
The training gear makes the heli more stable, so the gyro has less work to do. So a high gyro gain won't be obvious.
Once you remove the gear, the heli becomes more sensitive, and the gyro has to work more.
Then the high tail gain become obvious.
Just reduce the tail gain by a few % at a time, until it stops wagging.

 

[mooserider]

Oh that's right... I forgot the heli info: Trex 450 with a 3Gx. Sorry about that.

So the rudder gain... that's only adjustable on the Tx? Or is that the same thing as the rudder 'delay' on the 3GX. I don't know of any setting on the 3GX that's labelled as rudder 'gain', but re-reading the Trex's manual now, it sort of describes that behavior under setting the delay. But a few sections later, it talks about setting the gain, but doesn't mention how, other than using the Tx. Really confusing.

I'll go test out changing the delay and see if that helps.

 

[mooserider]

Well, I don't see any difference changing the delay. It's hard to know what it's set to while out testing, but I tried about 4 settings... 0 delay, a tiny bit, then about 25% stick and 50% stick settings. The higher delay just seems to worse it.

Maybe that's not the same as the gain?

I saw a youtube video where the guy swapped out the rudder servo and it helped. The tail servo I have came with the kit, but the kit is about 4 years old. It's the original Trex Pro DFC kit. The tail servo is not a micro, but it is digital. I have some extra new align micro servos... maybe I can swap that in. I have been wanting to move the tail servo to the tail boom and shorten the pushrod anyway. Would that possibly help? Tail servo isn't 'fast enough' maybe?

The tight-rope walker analogy is a great one btw!

Thanks!

 

[Lillyryan]

Yes try bringing the gain down on the tx. Just a few % at a time until it stops. Hopefully this will sort the issue out


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[mooserider]

I looked at the Tx, but I wasn't sure exactly how the 'gyro sense' % corresponded. It's set to 50%.

But I plugged in the 3GX to my PC and lowered the 'gyro head locking' setting via the software. That seems to have worked! There a tiny bit of wag left, but I'll tweak it a little more and see if it cleans up.

 

[Lee]

You don't want to adjust the delay.
If you are using a good digital servo it doesn't need any delay.
Its used when your servo is not as good quality and maybe slower then ideal.
The delay adjust the speed of the signal to match the speed of the servo.

 

[Lillyryan]

Cool. Glad you are getting there. As far as I remember you can adjust it on the pc or the tx. Glad she's flying better now.

 

[mooserider]

Thanks! Ya I put the delay back to zero after playing with it. Well, it's 10, but that's the lowest it goes (neutral rudder stick).

 

[mooserider]

Re: Tail wag

Hi all, this thread got delayed a bit because I had a crash when messing around with the 3GX settings. I thought I had fixed the issue, but I was mistaken at the time. However, last night I *think* I actually might have fixed it (will test more later today). Only had a few minutes last night in a dark parking lot to check it out.

Previously I was lowering the rudder locking gain to remove the tail wag. I went from about 65ish, slowly down to 45, and saw no change. After doing an absurd amount of reading online, and trying to filter that good from the bad, I went into the TX and increased the gyro gain by about 6%, and that seemed to dramatically help.

I still have no idea what the difference is between the 3GX rudder locking gain and the TX gyro gain, or how they work together. It’s mentioned in lots of online posts, that “if you lower the 3GX rudder gain, then you can increase it in the TX.†So, it doesn’t sound like they’re identical, otherwise lowering it in one and raising it in the other would just balance it out. And it did appear to help me with the tail wag. So I’m still wondering what these two do. I’ve searched online a lot, but still have don’t have a full understanding. I would love it if someone could fill me in so I’m not changing settings about stuff I don’t get.

I’m currently at 40 rudder locking gain on the 3GX, and 44 on the TX gain. Note that on the TX gyro setting in DX7, 50-100 is HH, while 0-50 is rate. So going from 50 to 45 is ‘increasing’ the gain for rate by 5%.

I also had some other questions… probably more for Tony, as they’re related in some degree to the 3GX setup and videos he made. Here they are:

** Delay (10 is the minimum) – My delay (in the software) is a minimum of 10. Moving the rudder either way during will only increase the delay. Why can it not go to zero? I do the setup for the delay just as was in the video, except that I push the button on the 3GX when I back off to 10 (since it’s the lowest).

** Setting center of sticks on 3GX first? – I read a few posts that mention the need to set the center of the sticks for the 3GX before you do anything else. I didn’t see that step in the videos. Is this true? If so I should go back through my setup again.

** Must be in HH mode for initial 3GX setup? – I also read some posts that state that you must be in HH mode when doing certain parts of the 3GX setup. Is that true that you know of, for say rudder setup or something? Maybe I missed that in the video as well.

** Rudder Travel Direction – this one I’ll probably have to make a video for. But in Tony’s videos he has a good closeup of the rudder correction direction… where he talks about the direction that the slider moves and the trailing edge of the blades. My trailing edges move the same direction as in the video (toward the direction of movement), but the slider moves the opposite way. I’m wonder if I just have an older model or something… I got this heli around 3 or 4 years ago. Not a big deal, cause the rudder is going the right direction, but it threw me a bit watching the video. Just kind of weird.

I’ve also include my current 3GX settings (images attached) in case it helps with any questions about the gyro (and other settings).

 

[holtneil]

Hi mate the tail delay will go to zero you have to move the rudder stick very slowly till its zero and small heil is still displayed then let the 3GX time out this will lock at zero ( if you press the button it will jump up to 10 again) so let it time out . I see you are using flybar sim , I am sure Tony has this turned off on the 450
As for wags on the tail your tail gain is 99% thats major high turn this one down till wag stops then you can up the tail locking gain to hold the tail better
I see you have the DX7 but mine was on the wrong channel for tail gyro gain so adjustments didnt change the gain , while you have the pc plugged into the 3GX adjust gyro gain in the transmitter and make sure the slider on the screen moves if it does not change gyro switch some use gear channel my DX9 uses aux2 so this may be stopping you getting gains right

 

[Tony]

I had a 3GX where I actually had to set it to 4 or something just to get 0 once the button was pushed. I never used the timout feature, might have to try it some day.

 

[holtneil]

Hi Tony I had to do it on both my 3GX units to get the zero delay on the rudder , if it did have the time out I would still be there lol

 

[Tony]

I may just have to stick a 3GX to the computer and play with this....

 

[holtneil]

Hi Tony its a real shame that the 3GX plays up , as its a easy gyro to set up , Align needs to look into it and sort the problems out , you can adjust it like the Kbar but the setting are named different , so this makes the Kbar super easy , the optimisation button on the tail and main rotor , is amazing you get the setting as close as you can click on the optimisation and go fly the heli , then plug back into PC and then un-click ,the gyro while in flight has set up tail and main rotor to its best settings

 

[mooserider]

Hotneil, thanks so much! You helped me figure out that the gyro was on the wrong channel. It needs to be on Aux2. So the gyro gain was stuck at max the whole time, and like you said, it explains why I saw no difference when changing it previously.

The delay I still can't get. I've messed with it so much, but it will only move from 10+, and will never go below 10 (when viewing it in the PC). It's definitely saving the settings... tested it out a bunch yesterday. But it's before the settings are saved... that I can't get it to zero.

Now that the gyro is working, I have new issues (of course). But I'll probably start a new thread so it's clearer. Everything on this thread was w/o the gyro working properly (or rather, with it maxxed).

Thanks to all you guys for the help on this. It's been brutal... getting there though. Maybe

 

[holtneil]

Hi glad the gain is sorted , I also had problems with delay, you need to move the rudder stick very very slowly to get it to zero ( small heli) its not always easy just as you get near it will jump stick with it till it is zero, then let the 3GX time out ,Dont press the button it will jump , when it times out it will lock the delay to zero
If I remember right I moved the stick to near full travel to start it moving but to get zero the stick was moving less than a mm

 

[mooserider]

Well you guys, I ended up not making that new post yet because I discovered/learned a bunch of stuff last night that helped a few things click. For some reason, I had it in my head that I was supposed to be flying in rate mode... and I wasn't, I was in HH mode. When I fixed the gyro to actually work (thanks Hotneil) such that I could adjust the gain, it was stuck in rate mode. And I suddenly had some serious rudder issues (pulls hard nose left). However, HH does work ok.

Basically, I think I have my TX programmed right now. I also set up two flight modes (normal and 'stunt'), such that one is in rate and the other in HH. And each have their own throttle curve, pitch curve, etc.

So here are the two new issues that I'm struggling with now:

1. Rate mode - it takes a LOT to hold the tail close to steady in rate. I probably don't need to use it for now, but I would like to know why this is happening, as I think it might be related to another issue (tail blow out). I have the rudder server at 90, the rudder slider is damn close to the middle, and the tail blades are straight. 3GX rudder setup was redone of course. To keep the tail stable, I need to give it a good 6 or 7 clicks of rudder trim and set the gain to pretty much 100%. However, with none of that trim, and just a little gain in HH mode, it holds stable with no issue. That sort of blows my mind! Basically, all the trim added in rate mode makes the slider way over to one side, so there's less additional room to move. Yet HH has no issue with it with no trim and way less gain. It's not like the rudder slider has any additional room to move in HH... so why such a difference? The only thing I can think of is to set up the rudder with a decent amount of right rudder already at neutral stick, but that seems like a bad idea too.

2. Throttle curve - I have had a tail 'blow out' issue since I got this thing flying. In all the various settings I've gone through, even the latest, which I thought for sure I had found the problem. Last night I was re-reading some of my earlier posts and responses, and one of the users mentioned something I thought would solve my issue... that I was using a linear throttle curve. The idea being, above mid-stick, the motor revs higher, increasing the torque and making it spin. So I figured out the throttle curve and instead of linear (0, 25, 50, 75, 100), I changed it to (0, 25, 60, 65, 65). However, for one this didn't help much, maybe a little... but secondly, the throttle curve doesn't behave the right way. Just after lifting off at mid stick, the head speed drops. Not from drag, but through the throttle channel. If I'm still on the ground, lowering the stick from about 65% down to 50% position, will INCREASE the throttle. I really don't get this. I tried several various settings, like 0, 25, 60, 75, 85, just to make sure it was increasing constantly, but the same result. When I set it to linear though, it works like normal on the head speed.

If you have any thoughts on either of these issues, please let me know!

Thanks again all!

 

[holtneil]

Hi Mate some of this may be a linked problem , to get the tail spot on we need to get in to rate mode , ( not a windy day dead claim is best or indoors) now pop the heli into a hover the tail will drift to right or left , Now correct the rudder with the stick note which way you move the stick to stop the drift.
Now land and adjust the rod ( now the tick is move the stick in the direction you moved it when flying to stop the drift and watch which way the rod moves , say it moves towards the tail gear box this now tell you you need to make rod longer, if the heli is old school and servo is mounted on tail boom just slide servo along boom towards tail gearbox, only a tiny amount then hover again, keep doing this till heli does not drift any more, Now pop in to HH mode the tail will be locked in better , this may help with the blow out so do this setting first ,I set up all my helis this way and the tail even rate does not drift
If you fly scale then fly in rate mode this will give you a nice banked turn, if just flying pod and boom you can still fly rate but most guys fly HH mode