Tail soft oscillations while giving left rudder. Right rudder is fine instead.
09-13-2009, 04:59 AM
#1
Thread Starter
Tail soft oscillations while giving left rudder. Right rudder is fine instead.
Hi all,
I need your big help Trex700 experienced users and flyers :
Here’s my problem :
Just finished and flown first 7 tanks of my Trex 700 : marvelous! After have flown since last 3 years with trex250, trex 450, trex 500 and trex 600, this is my first i.c. hely.
So far no particular problems found on set-up and Align 91H motor break in.
For now I’m just hovering the model and doing some slow flight. 1700-1800 Rpm of rotor speed. Everything looks so fine.
The main problem I have is as follows : while giving left rudder the hely surely dows the lest rotation over it’s vertical axis, but it does oscillating. I try to be much more clear : while aI gently give left rudder (to start a gentle left ruder turn) it seems that the rotation after 15degrees is – in a certain way – contrasted by the gyro. Then , it continues and again soflty tends to stop, then again it continues until the point I cancel the left input with the stick.
Turning right, instead, if fine, slow or fast no that strange “counter-contrast” maden – I imagine – by the gyro.
Now, here’s few details :
The gyro installed is the Align gyro, servos are digital Savox 1274TG, very fast and precise, no other problems.
My tx is – like in the last 7 years – a Futaba T9ZAP WC2 with wich I fly all other helys I have.
These my doubts / question to understand what the cause can be :
To have no wag on the tail (I do not do acro or 3d, just normal flight) with Align gyro installed I need to keep the gain around 45%, that is around 10% in a 0-100% AVCS scale, since with T9ZAP gyro AVCS gain is 0-50% , then 51-100% is Normal mode. So, you see that to have a steady tail I need to have a quite low AVCS gain , close to Normal mode. With other helys and gyro I have (GY401 and others) I normally stay around 30/35%, that is more or less at mid AVCS scale, not for sure very close to Normal mode.
Also, Align gyro has been perfectly programmed, like many other, it’s quite easy to set, so it works fine, AVCS, the gain I set from tx is exactly what it shows and so on. No doubts, except the left and right limit to set on it. I see that on Trex 700 tail there’s lot of pitch available on the tail, so which is the best limits setting ? around +/- 8 degrees of pitch on tail blades ??
Also, the very low gain I need could mean something particular about mechanical setting of tail command ? I set the tail per instruction and with the same basic concept always used with Align helys, that is tail servo centered (as less sub-trim as possible, in my case 10%), everything 90 degrees and tail slider more or less at center position.
On tail servo, I use the classical Futaba 4 points star, with 4 holes per point, having put the ball on the 3rd hole from the center so that with all the servo throw (no reduction) I cover all the tail slider stroke, without binding.
Could be the ball link on the 3rd hole of the tail servo star too out from the center and so producing a too much sensible gyro reaction … considering that to have everything steady I have to keep the gyro gain very reduced, quite close to the Normal mode ??
I’ve tried to put some expo on tail channel, but nothing changes … even if I try to rotate the hely left as gentle as I can, the oscillation counter the gyro still is there .
If I try to give left rudder with more violence the oscillation is even more accentuated, as if really the giro would be trying to stop the rotation, while I’m keeping the left command.
I repeat, when and if I give right rudder, everything is perfectly fine.
I remember that at the beginning I have a similar problem with trex 250, same left rudder turns , but there I have a different gyro (Logitech) and the comparison is too different. Anyway, in that case, I played a little bit with “reaction speed” setting on the gyro and now has disappeared.
On the trex700 the situation is very different, different model, different servos and gyro and inertia .. different. BUT the problem is the same I have : left rudder = left rotation on vertical axis but done through 2 / 3 oscillation that try to counteract the rotation commanded itself.
One thing I know for sure is that here in Italy and Europe this configuration of servo and Align gyro is very common and used so I’ve no doubt about electronics I have at least.
I really look forward to receive any your idea or suggestion you can have, every one - even if simple or improbable – will be very well appreciated by me, so please feel free to consider every possibility and reply here to help me to solve this slight issue with this marvelous model.
Everything coming from your experience will be of great help for me, considering my lack of experience on these kind of big models and with trex700 in particular too.
Thank you very much to you all!
Kind regards,
Denis Ferrari
I need your big help Trex700 experienced users and flyers :
Here’s my problem :
Just finished and flown first 7 tanks of my Trex 700 : marvelous! After have flown since last 3 years with trex250, trex 450, trex 500 and trex 600, this is my first i.c. hely.
So far no particular problems found on set-up and Align 91H motor break in.
For now I’m just hovering the model and doing some slow flight. 1700-1800 Rpm of rotor speed. Everything looks so fine.
The main problem I have is as follows : while giving left rudder the hely surely dows the lest rotation over it’s vertical axis, but it does oscillating. I try to be much more clear : while aI gently give left rudder (to start a gentle left ruder turn) it seems that the rotation after 15degrees is – in a certain way – contrasted by the gyro. Then , it continues and again soflty tends to stop, then again it continues until the point I cancel the left input with the stick.
Turning right, instead, if fine, slow or fast no that strange “counter-contrast” maden – I imagine – by the gyro.
Now, here’s few details :
The gyro installed is the Align gyro, servos are digital Savox 1274TG, very fast and precise, no other problems.
My tx is – like in the last 7 years – a Futaba T9ZAP WC2 with wich I fly all other helys I have.
These my doubts / question to understand what the cause can be :
To have no wag on the tail (I do not do acro or 3d, just normal flight) with Align gyro installed I need to keep the gain around 45%, that is around 10% in a 0-100% AVCS scale, since with T9ZAP gyro AVCS gain is 0-50% , then 51-100% is Normal mode. So, you see that to have a steady tail I need to have a quite low AVCS gain , close to Normal mode. With other helys and gyro I have (GY401 and others) I normally stay around 30/35%, that is more or less at mid AVCS scale, not for sure very close to Normal mode.
Also, Align gyro has been perfectly programmed, like many other, it’s quite easy to set, so it works fine, AVCS, the gain I set from tx is exactly what it shows and so on. No doubts, except the left and right limit to set on it. I see that on Trex 700 tail there’s lot of pitch available on the tail, so which is the best limits setting ? around +/- 8 degrees of pitch on tail blades ??
Also, the very low gain I need could mean something particular about mechanical setting of tail command ? I set the tail per instruction and with the same basic concept always used with Align helys, that is tail servo centered (as less sub-trim as possible, in my case 10%), everything 90 degrees and tail slider more or less at center position.
On tail servo, I use the classical Futaba 4 points star, with 4 holes per point, having put the ball on the 3rd hole from the center so that with all the servo throw (no reduction) I cover all the tail slider stroke, without binding.
Could be the ball link on the 3rd hole of the tail servo star too out from the center and so producing a too much sensible gyro reaction … considering that to have everything steady I have to keep the gyro gain very reduced, quite close to the Normal mode ??
I’ve tried to put some expo on tail channel, but nothing changes … even if I try to rotate the hely left as gentle as I can, the oscillation counter the gyro still is there .
If I try to give left rudder with more violence the oscillation is even more accentuated, as if really the giro would be trying to stop the rotation, while I’m keeping the left command.
I repeat, when and if I give right rudder, everything is perfectly fine.
I remember that at the beginning I have a similar problem with trex 250, same left rudder turns , but there I have a different gyro (Logitech) and the comparison is too different. Anyway, in that case, I played a little bit with “reaction speed” setting on the gyro and now has disappeared.
On the trex700 the situation is very different, different model, different servos and gyro and inertia .. different. BUT the problem is the same I have : left rudder = left rotation on vertical axis but done through 2 / 3 oscillation that try to counteract the rotation commanded itself.
One thing I know for sure is that here in Italy and Europe this configuration of servo and Align gyro is very common and used so I’ve no doubt about electronics I have at least.
I really look forward to receive any your idea or suggestion you can have, every one - even if simple or improbable – will be very well appreciated by me, so please feel free to consider every possibility and reply here to help me to solve this slight issue with this marvelous model.
Everything coming from your experience will be of great help for me, considering my lack of experience on these kind of big models and with trex700 in particular too.
Thank you very much to you all!
Kind regards,
Denis Ferrari
