Help! Wierd gyro problem

[Kwaz]

Hope someone can help. I have a GWS 800 gyro in my Mini Titan hooked up with a non-digital hitec servo all sitting in an Agusta fuselage). This gyro is a clone of the GY401 I think(?)

Problems
1. Sometime I get a very slow drift on the nose i.e. you point the nose in one direction and it very slowly turns
2. I'm trying to do a single fast pirouette. I put in a large rudder deflection and the nose starts going around and then I return the rudder stick to neutral after one 360 degree rotation of the heli but instead of the nose stopping dead , it keeps on spinning and does another complete pirouette! It feels completely out of control!

Settings on Gyro are :
servo - non digital
delay - 0

On my DX7 the gyro senitivity is set to 80%. I have mechanically set the rudder to neutral on the heli with the sensitivity set to 0%. In hover and forward flight the heli seems to behave itself and there is no hunting on the tail.

Any idea what's causing these problems? Or are the GWS gyros just not very good!? I have another mini titan with a Futaba GY401 and futaba digital servo and the tail is rock solid and stops immediately when the transmitter stick is moved to neutral.

[Kwaz]

oops sorry would help if I got the gyro name right!

It's a KDS 800. Not a GWS 800

[Murdanny]

just my 2 cents, i think the problem lies in your tail servo. to have a good tail behaviour, try to keep all tail servos at least digital. The faster your tail servo the better of course.

cheers.

[nacar]

For non-digital servo, try with some delays in your gyro setting.

[Kwaz]

For non-digital servo, try with some delays in your gyro setting.

I can give that a go but just wondering if that will actually make the problem worse - because at the moment the gyro/servo seem to be lagging behind what I want the heli to do (i.e. I retun the stick to neutral but the heli keeps spinning)

How to do I know how much delay to use or is it just a case of experimenting....

[nacar]

Just experiment. Maybe can try at the mid point first.

[pck]

Hi Kwaz, you mentioned that this heli is in a Agusta fuselage. Could there be some binding occuring on your rudder mechanism? Or that your rudder linkage rod is 'rubbing' inside the fuselage?

The other thing to check would be to make sure that your tail unit is protruding out from the fuselage, if not, you may need to do some filing to widen the opening to allow free movement of the tail rudder unit.

[Kwaz]

Thanks for all the suggestions. I'll have a play around with the delay and double check there is no binding and see how I go.

[Kwaz]

I did some side by side comparisons between the KDS800 and the GY401. All tests done on the bench not in flight, with AVCS on.

I noticed two key differences;

1. The KDS seems incredibly insensitive to slow rotation even on 100% gain. If I pick up the heli and slowly rotate it, the KDS does not make any corrections to the tail servo. When I do this with the GY401 it is practically impossible to rotate the model without the tail servo making a correction (although it is possible if I rotate the model *incredibly* slowly). This I think accounts for why my model with the KDS installed has a slow drifting nose.

2. With full and prolonged rudder stick deflection, the KDS will move the tail servo to the end of its travel. Moving the rudder stick back to neutral does not move the servo off its end stop. With the GY401, the same thing happens except when the stick is returned to neutral, the tail servo moves a few MM off its stop. I don't really know what this means in practical terms however. I have a feeling this behavior might account for the unstoppable piro problem I have on the Agusta.

My conclusion from doing the tests is that the KDS just isn't really a great gyro! I've no idea how people would use it for 3D flight - even getting it to behave during normal flight seems problematic? Perhaps this is to be expected from a gyro that costs less than half the price of the futaba.

I had a play with the delay setting and it just made the problems worse.

Anybody with a KDS gyro that would care to comment??

[Ghostfit]

Try increasing the EPA on your Rudder in the Tx menu.

[misato]

To start, I am a beginner that's learning to hover with training kit.

I used to own a KDS800 Gyro. It looks like a GY402 clone, but sadly it doesn't perform like one. I experienced some of the same issues as Kwaz, tail drifts slowly on its own, the tail don't stop dead at neutral stick but instead still continues a bit before it finally stops. Setting the gyro gain doesn't really help too much.

[premonition08]

heres a link for tail gyro and servo setup

http://www.trextuning.com/modern-gyros.php

[premonition08]

i've set my tail servo and gyro in rate mode, i hover in rate mode and adjust accordingly (mechanically and not by subtrim) until my tail holds during the hover, then i switch to heading hold. got my g401b drift free!! piro rate CW and CCW are the same