450 Trex 450L with gPro - Dolphin effect

[Erfan]

Hi

I just build a new trex 450L with gPro. No vibrations, no oscillation but it has a "dolphin effect" on FFF. I tried to lower the swash gain 5 clicks at the time all the way to the lowest setting, did not do much.
I tried going the either way, did not help either, strangely I could have max gain on swash and no oscillation which is strange, but nothing changed when it comes to the dolphin dancing on FFF.
And the head-speed does not seem to help either, tried different settings there as well. Small v-curve around 70% and then on 85% and last at 95%.

Everything is brand new, never crashed. Nothing is bent, no vibrations what I can see, it does not wobble or oscillation issues on swash or tail.
The servos are Align DS430M. Two of them are brand new, the third one is a used since before and its sitting on elevator. But behaves as it should from what I can see, no stripped gear.

Before I change the servos (I got 3 Align DS416m in the package) I thought checking with you guys, any suggestions on what it could be?
And how come there is no oscillation even with the highest swash gain, isn't that strange? I have only changed settings through the bluetooth (on iPhone and Andriod), it seems to update everything when I change but perhaps there is a bug?

I have build one exactly the same before using another gPro gyro with stock settings, it flies perfectly... But this one just does not want to behave

 

[Erfan]

I think I found the issue, the elevator servo arm has the ball in the inner hole while the other 2 swash servos has it on the outer.
They should all be on the inner hole...

I'll change and test again tomorrow, hopefully that will solve the issue.

 

[Smoggie]

Yeah, that would certainly do it!

 

[Erfan]

So I was out today and tested after moving the elevator ball to the inner hole. But no luck, it still has a bit of dolphin effect.

I also noticed it has almost no positive pitch power. The head is 0c at mid-stick and around +-11 at high and low. But when it comes to positive pitch it has no power, it goes really slow upwards.
If I fly inverted and give full negativ pitch it just pops up in the air (upwards). But the pitch is the same for positive and negativ, I double and tripled checked.

I bet this is somehow related to my issue with the dolphin and the fact that max swash gain or min swash gain does not matter, no oscillation on max swash gain which is strange.

The gPro manual says that dolphin effect on FFF most to do with either bad servo or linkages. I wonder if the elevator servo could be the problem since that one is the only used part on the heli.

 

[Tony]

If just the elevator servo was to blame then you would notice hard pitching when doing a punch out, not just being slow. This almost sounds like you have a speed limiter set on the collective. But only on positive. Have you tried going through the setup process again? Maybe there is something that is just not quite right in there somewhere. Unfortunately I have not had a chance to play with the GPro gyro at all. So I'm not that much help here.

 

[Erfan]

Speed limiter? Is that in the radio then? I have not seen anything like that in the gPro, and I'm pretty sure I have not messed with anything liked that in my radio (Futaba 14SG). But I will have another look.

 

[Tony]

I know they have a rotational limit on degrees per second (I think), I'm just wondering if they have something like that for pitch as well.

 

[Erfan]

No they don't have that anymore, I know what you mean, they did have it on the 3gx if I'm not mistaking but they don't in gPro.
The rate for cyclic is a stupid bar from 40 (stable) - 120 (quick), same goes for cyclic response or what they call "Flight Agility" the less you have the more flybar it feels.

Its a shame they don't talk in terms of degrees/s which makes sense. I have attached a pic with some example values, not what I have on my 450. But at least you can see how the software looks.
There is also a setup tab but that is only for setting up trims, swash movement, tail endpoints etc...



- - - Updated - - -

The example values are actually the default values, which on another t450L was really good. But on this one is does not work as good.
But have you ever experienced max cyclic gain with no oscillation? I cranked the swash gain all the way up (120) and there is no oscillation which seems really strange. I have never had a gyro which didn't freak out with to much gain.

 

[Tony]

It's almost like a dumbed down version of a gyro software. Very interesting. Wish I could have gotten my hands on one of these.

 

[Erfan]

And the size is set to small heli, not large as shown in the pic

- - - Updated - - -

Well if I don't get it working soon I will send you mine...
Its a shame because it actually behaved really well on another 450L, I was surprised since Align never could anything work really well
And the setup is really easy as well, almost like Ikon/Brain setup.

I have ordered a new Align ds430m servo and I will try it with all new servos and see if that will fix anything before I get a trusty Ikon for my 450. Love the Ikon, I have it on my 700, its perfect!

Btw, if you want to see the program, just download the windows version from align, the have a demo mode were you can see the setup and everything else. Just press the setup button or paramater button after the app starts and it will ask you if you want to go into demo mode since it does not find a gyro.

 

[Erfan]

Well, I got it working when I installed a new servo for ELE. It still had minor dolphin effect but it got better and better each time I played with the swash gain. It flew almost great and had a lot of pitch power.

But then 3 batteries later it lost all positive pitch power, full pitch barely got it above ground. I have double checked the pitch, it has +-11, I even tried with +-12.
Did the setup again, everything is perfect on the bench and the head speed looks good but it has no pitch power at all

Strangely it has no problems with cyclic pitch, both ELE and AIL works great but there is no collective pitch.

Any ideas what could cause that? Are we talking about bad servos or bad FBL?
I took of the head links and both grips move without any issues or binding, I also re greased the head bearings and trust bearings.

The setup is: Trex 450L 6S with 360 blades, added the FL head instead of the DFC head to spare the servos in a crash.
Align DS430M servos, Align 525 tail servo and stock align 6S motor and ESC, also the ESC is giving 6v from the BEC.

It almost feels like it does not have enough power to the servos when the head speed picks up or something. Although the cyclic power is there, perhaps collective pitch takes more power and cyclic pitch.

 

[trainrider06]

So does the swash move up and down full throws? If it looks limited I'd guess a bad servo on pitch. I forgot to look was it a BeastX your using?

 

[Erfan]

Everything works without pressure on the blades but as soon as the blades starts spinning I lose almost all collective pitch.
I found 1 bad trust bearing in the head, even with lot of grease you could feel the balls and it felt gritty, I have order new ones and I will try.

But I never heard of bad trust bearings behaving like this but perhaps under full load of the blades it becomes to much for the bearing and the head gets stuck.
Besides that I have no idea, even checked output voltage to the servos, the FBL sends out 6v.

 

[Tony]

Have you checked the voltages going to the servos while the helicopter is under power? I'm wondering if the ESC is sucking voltage from the BEC..

 

[Erfan]

That is exactly what I did, put it on 95% load and tested one of the servo outputs, it helt around 5.6-6.0v
I only tested one of them thou but I can't imagine one of the outputs giving 6 and other ones below 5 or even less. Perhaps I should have tested them all?

 

[Tony]

Nah, they are all on the same trace in the gyro. Only thing that changes is the signal.

Is there any way you can get a video of what it's doing? Might help.

 

[Erfan]

Well I don't have any trust bearings any more, threw away the old ones but new ones are coming tomorrow, hopefully I could perhaps make a video during the weekend if anybody else is out on the field.

 

[Tony]

Remove the feathering shaft and dampers from the head block and do a test like that. Also remove the tail blades if you have not done so already. With a bare head, does the issue still exist?

 

[Smoggie]

If the blade grips feel notchy when turned that's hardly ever thrust bearings to blame. The problem is virtually always that the inner radial bearing is getting 'squeezed' too much by being compressed against the head damper, which gives a notchy feel. If there are shim washers fitted you can remove them or replace with thinner ones to resolve it.

As for you losing collective. Often that's due to having vertical play on the main shaft so that when you apply pitch the whole shaft and head assembly lifts up and by doing so reduces collective pitch.

 

[Tony]

Unless of course the grips were tightened too tight. That could cause the balls to divot the thrust washers. But a LOT of force is required to do this. Just bored and thought I would mention lol. But yes, the radial bearings are more likely.