Problems with piros in fast traslations - Devo 8s

Hi Everyone, I am not 100% sure about it is a Deviation issue on my Devo 8s. I have two helicopters a Tarot 450 Pro and a T-Rex 600 and with both I have the same problem while flying.
If I try to make a piro on either side (mainly to the right) when I go in a fast traslation, I mean straight forward applying a bit of throttle to accelerate, neither of my helis turn with ease when give right rudder (move the rudder stick to the right) or left rudder (less noticeable). I am pretty sure that there is not mechanical issue, nor FBL misconfiguration. I have tested electronics, cables, servos,... so I rule out that. It also happens to me (but less noticeable) with my micro heli Hisky HCP100s.

So my question is, What config parameter can make such a kind of weird behaviour?
I attach my models here. Next step I am going to test is to create a "standard" model and not use the Advanced GUI. Please, if you have some ideas they are welcome, I run out of them...

Deviation Version: devo8-v4.0.1-4062def

Thank you!!

Hi, No one has ever happened something like this? I can tell that it happens even with my Hisky HCP100s so is quite probable that is a Devo transmitter issue or a misconfiguration on the models.
Next week I will try the same manoeuvre with a Spektrum DX8 to check it out, but I would like not to change my beloved Devo transmitter for this weird issue.

Please, if you can test in field with your heli or have a look to my models, may be you find something wrong that I can apply.

Thank you.

this is possibly a mechanical issue, as turning the tail against the torque of the main blades requires more power than with it, also as you are adding power at the same time you are increasing said torque

No, I am completely sure is not the case.
I have been looking for a year for that kind of mechanical issue on my 450. After give up with the 450 I bought a second hand T-Rex 600 and I was astonished because I had the same issue. Both helicopters are quite different, but share the same mechanical rear rotor so still there were a little possibility that both had the same problem but I ruled out when testing with my micro heli Hisky HCP100s (it uses even other kind of protocol), that has a tail brushless motor. Doing the same fast translations or if I want to make a fast change of direction, the helicopter get stuck and doesn't turn.
The only common part of the three helicopters is my Devo transmitter. As I cannot believe is a hardware issue, I bet is a configuration issue but I don't know what could be, that's why I posted my models just in case.

Tried some maneuvers with this in mind today with a MCPx BL. Didn't notice any issues with rudder response. My skills are intermediate so maybe I wouldn't know. Haven't noticed any issues with my 450 either.

If you're just hovering there's no issues with yaw rate?

Hi, sorry. I didn't see your response.

When hovering there isn't any issue while rotating, it is just on fast translations, the more fast I go the more noticeable is the issue.
Here you can see an example while flying my 600 helicopter. Please HD and full screen...



Go directly to 1m 53s. It is just the time when I try a piro on the air, applying full right rudder. Please replay to realize that the piro starts OK, then the helicopter stuck at 90º and then make the full piro after a while. Left rudder has the same issue but is less noticeable logically.
The same behaviour happens on my 450 and my micro heli Hisky HCP100s.

I have made some workbench tests to check that the tail rotor get the full pitch angle right and left on my 450, and yes, it works as expected.



As I said, the only possibilities are Devo firmware problem or some misconfiguration on my models config.

I appreciate any advice.
Thanks!.

the fact you have full rudder pitch rules out a devo issue, i'd suggest mixing some extra throttle to rudder, using larger tailblades, a gokd govener and cells, also tuning the tail gyro gain. I still say it's a mechanics issue (not mechanical) where as you are at the point of lowest headspeed and as such tailspeed, you notice as soon as your tail is on the downside of the piro it's fine again.

my 2 cent: use bigger tail blades or/and increase rpm. Many Align helicopters are known for their weak tails, they need high rpm. Have the same issue on a Logo500 (not flown with a Devo) when trying to pirouette at full speed. You may also try to increase P-value for your tail gyro / FBL tail axis. This is clearly not a devo issue.

One thing you also can test if possible: use a conventional gyro on your tail and see if the problem decreases. If yes, you have a kbar problem.

Have success

ThomasC

Hi ThomasC and all, thank you very much for your responses.

Yesterday I were with some friends flying at field and analyse the problem all together...none of us were able to find out what the problem could be.!!!

I tested again with my 450 (3s) and 600 (6s) helicopter and I confirm it happens again, very noticeable. On my 450 I changed the main motor for a Scorpion 2221-8 (150T main gear, 13T pinion - 100% rpm = it is almost insane for a 450 with full lipo) to get more power and torque while flying in fast traslations, tail blades are the longer I can install, tested with carbon and plastic. I have also tested with two different Kbar, one GV8000 and one Tarot ZYX which is totally different and nothing changes, same behaviour. So I rule out a Kbar issue.

I agree is not a Devo issue, but is the only common thing between all my helis.... I wonder if someone has tested the same manoeuvre the same way, may be is totally normal and still no one has notice????. Remember that my Hisky hcp100s that is a 2s micro heli with brushless tail motor, do the same. One of my colleagues has lend to me a Spektrum Dx8 to rule out the Devo as well, let's see...

I will try changing the P-value parameter, I don't really know how to "manage" this value or how it will affect to tail but It is worth to test it. Thanks.

@Fernando: I don't think that this is your problem, because your tail blade holders already have the "chinese weights" built in, but one more thing you could check is pushrod forces for your tail. When those are too high, servo speed decreases and possibly tail authority decreases, too. See - simple solution in case forces are too high: use longer screws and add a screw nut on each side, works just like heimjoint's chinese weights. Had to do this (more than one additional nut) on my KDS 450SV tail, which has no chinese weights built in.

As already said, I have a Logo 500SE and have the same problem (Logo tails don't need chinese weights as they are designed nearly perfect). FBL is a Graupner GR-18, TX is Graupner, too (of course). A perfect tail is quite difficult to achieve, none of my helicopters pirouettes perfect at higher speed. I have a Walkera V120D02S with GY280RX (FBL with integrated DSM2 RX) and flew it with my Graupner TX (DSMX-module added) and also with a DeviationTX Devo10. Absolutely no difference.

Have success

ThomasC

Good to know someone else have the same issue, I was driving me nut...

I am going to change the metal tail servo rod by one made with carbon to prevent bending while the servo pushes. The one I use is the popular KST DS215MG, powerful enough (I think) for tail use, actually, lots of people use them. In my 600 I uses the Futaba 9254, plenty of power as well.
About the chinese weights...I have never heard anything about it, anyway, I already have changed the original "simple" tail rotor by the newly made Thrust tail blade holder, is a little heavy and movement is softer as they use the same "open" bearings as on the main blade holders.

A friend of mine said that is quite likely this problem could be minimized by using a 6S configuration on my 450. May be he is right.

Hi everyone, I cannot get rid of this issue.... Can anyone upload a 450/600 model just to compare the basics and check if I have something wrong?
Is not a 6S matter as a friend of mine has the same helicopter flying with a futaba and works perfect.

Thank you!