Rudder flutter problem...
#1
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Rudder flutter problem...
I am pretty sure that the flutter in the video isn't supposed to happen but I'm not sure what is causing it or how to correct it?? It happens with both small movements, large movements, as well as, letting it snap back to neutral. I thought maybe it was the position of the control horn, but it looks aligned with the rudder hinge. This plane is a .61 Reactor Bipe, and the servo is Futaba S9650 (digital).
Anyone have any idea's?
[youtube]http://www.youtube.com/watch?v=ZkyBYSg_U58[/youtube]
Anyone have any idea's?
[youtube]http://www.youtube.com/watch?v=ZkyBYSg_U58[/youtube]
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RE: Rudder flutter problem...
ORIGINAL: da Rock
Ideas?
Yes, swap out the servo and see what another one does. Older servos would do that when they needed cleaning.
Ideas?
Yes, swap out the servo and see what another one does. Older servos would do that when they needed cleaning.
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RE: Rudder flutter problem...
Yup, looks like a dirty or worn out servo to me, too. They're usually not worth trying to clean and you'll probably never get all the dirt out. Scrap it.
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RE: Rudder flutter problem...
if swapping the servo don't help, from what i can see in your vid it could be the rudder is not rigid enough thus it's flexing/vibrating by itself(?)
#6
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RE: Rudder flutter problem...
The servo is brand new, just installed. But I will try to swap it out with another when I get chance tonight.
Thanks for the replies!
Thanks for the replies!
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RE: Rudder flutter problem...
ORIGINAL: vasek
if swapping the servo don't help, from what i can see in your vid it could be the rudder is not rigid enough thus it's flexing/vibrating by itself(?)
if swapping the servo don't help, from what i can see in your vid it could be the rudder is not rigid enough thus it's flexing/vibrating by itself(?)
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RE: Rudder flutter problem...
To me it sounds like you are letting the stick just snap back to center on the TX...
if this is the case then the servo is doing exactly what it is being commanded to do.
if this is the case then the servo is doing exactly what it is being commanded to do.
#10
RE: Rudder flutter problem...
I bet a fully charged high voltage pack with enough slop that the servo is over centering. Happens with digital servos. I bet it does not do it with a pack that has been drained a bit like a flight's worth.
#12
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RE: Rudder flutter problem...
First off, this is not flutter, at least not in convention definition of flutter. Instead it is an oscillation which can be caused by several factors. The more probable in this case is a slightly sticky push rod that has a lot of friction to movement near the center position. It could also be caused by the rudder hinges not being in perfect alignment causing them to be at rest in the not-quite-neutral position and wanting to snap to a slightly off set position an neutral. It could also be a dirty potentiometer in the servo itself or a well worn one. If it is the servo, you should be able to see the servo jitter when the rudder push rod is disconnected from the servo. If, with the rudder push rod disconnected from the servo, the servo does not jitter then it has to be friction in either the push rod or hinges on the rudder and the servo has a clean bill of health.
#14
RE: Rudder flutter problem...
I agree with Rodney; that is not flutter.
The amplitude of the oscillation shown in the video gets smaller with time, instead of bigger or reinforced by the airstream.
It is just like a deflected spring that is liberated.
The reason is the same as for the spring: elasticity of the whole system formed by servo, linkage, horn, hinge and control surface.
The amplitude of the oscillation shown in the video gets smaller with time, instead of bigger or reinforced by the airstream.
It is just like a deflected spring that is liberated.
The reason is the same as for the spring: elasticity of the whole system formed by servo, linkage, horn, hinge and control surface.
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RE: Rudder flutter problem...
I just checked on the Futaba site...the S9650 servo is only recommended on electric powered cars......where a servo searching for center such as yours is, is no biggie.
You have the wrong servo..and it seems a little weak for rudder
Good luck
You have the wrong servo..and it seems a little weak for rudder
Good luck
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RE: Rudder flutter problem...
Problem solved. Was a combination of a couple of things. First, I repositioned the linkage on the servo arm and control horn (I think this was the biggest problem), then I made sure there wasn't any slop in the linkage. Problem gone!
Thanks for everybody's help.
Thanks for everybody's help.
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RE: Rudder flutter problem...
I had this happen last year with a new digital servo on the rudder of a Venus II. It went away when I reduced the rudder throw by moving the clevis to the outside hole on the rudder horn.
I believe it's caused by a combination of a heavy rudder (lots of inertia) and the narrow deadband of digital servos. The rudder overshoots neutral because it's so heavy, the servo corrects, the surface overshoots and the whole process repeats itself.
After I reduced the throw I flew the whole season without any problems.
I believe it's caused by a combination of a heavy rudder (lots of inertia) and the narrow deadband of digital servos. The rudder overshoots neutral because it's so heavy, the servo corrects, the surface overshoots and the whole process repeats itself.
After I reduced the throw I flew the whole season without any problems.
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RE: Rudder flutter problem...
ORIGINAL: j.duncker
Common problem nowadays with digital seros and any large control surface.
Common problem nowadays with digital seros and any large control surface.