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« on: October 31, 2015, 08:54:58 AM »
satz flying
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I have serous flutter problem in rudder and elevator servo of my Extra 330 EPP plane.

Couldn't find out the reason. Kindly help me out.
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« Reply #1 on: October 31, 2015, 06:48:19 PM »
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Many many possibilities

First: eliminate a servo problem: remove the servo from it's mount and test it through the full operating range. If you notice any shudder jitter or jerks, the servo is bad and should be replaced

If the Servo is OK, check the load condition on the push rod. It should not be pre-stressed and free to slide up and down. If it is, free it up. Ensure the push rod is as short and as straight as possible.

Some photos of your installation would be helpful.
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« Reply #2 on: October 31, 2015, 08:40:16 PM »
satz flying
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Thanks you sir. I will upload some photos as soon as possible.
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« Reply #3 on: November 01, 2015, 08:10:55 AM »
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Of course, I have assumed as you said the "flutter" is in the servos, not the control surfaces. But that will become clear when you eliminate the servos and pushrods having issues.

There is also another situation, unlikely though: the rx output is itself non-linear!
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« Reply #4 on: November 01, 2015, 09:33:36 AM »
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Well..... if I may add my two bit on the topic of Flutter.....

Well it could just not that the servos have the flutter..... if it is so... just change the servos and find out....

Assuming that your servos and control links do not have much play in the linkages.... so play will always remain but it should be as small as possible...
Flutter is basically a problem which is encountered on control surfaces because the control surface is not correctly balanced with the main wing / stabilisers.  Flutter takes place on all types of control surfaces and reasons of the same can be understood one the aerodynamics if Flutter is understood.  In face Flutter takes place in all structures which are subjected to Aerodynamic forces....

You may like to read the following links....
http://www.wired.com/2010/03/flutter-testing-aircraft/
http://www.iitk.ac.in/infocell/Archive/dirjan1/flutter.html
https://en.wikipedia.org/wiki/Aeroelasticity

This link explains the issue and gives a few methods to correct it for aeromodels.....
http://www.rccr1957.com/flutter.pdf

However in my understanding of aerodynamics.......

In aeroplanes where the manufacturer is guarding against flutter because people are involved, he spends money to do the tests and get the optimum conditions to reduce flutter....

For us aeromodellers who often make out own planes and most often then not there are a hordes of irregularities of balancing and streamlining.... we will have to live with flutter.....  Just check your model for the points as stated by Sanjay Sir.... and make sure of a few things:-

1.  That the control surface is not made of a heavy material.... as it will result in the CG of the elevatore or the rudder falling behind the hinge line.
2.  That the hinge line is located as close to the GC of the control surface as far as possible....

BOTH THESE CONDITIONS ARE DIFFICULT TO ACHEIVE.

3.  In case you can give an aerodynamic balance to the control surface you will eliminate most of the flutter... something like given in this picture.... http://img.tfd.com/mgh/av/th/f0017-01.jpg
and you may like to read this....
https://en.wikipedia.org/wiki/Balanced_rudder

Best wishes and Happy and Safe Flying......


by the way.... my models also show signs of flutter as I have not used most of these remidial actions on my models.  All my models are self made but I do ensure that I give some balancing and that my control surfaces are very light Balsa....  Yes they still flutter...
« Last Edit: November 01, 2015, 09:53:54 AM by shobhit17 » Logged

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« Reply #5 on: November 01, 2015, 10:53:38 AM »
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you probably mean servo jitter - i.e servo making small random uncommanded movements on its own.

if that is the case then

a. twist the servo leads to remove unwanted interference
b. put a toroid in the servo leads.

if prob is still not cured then open up the servo and squirt some electrical cleaner like CRC26

if you mean control surface flutter - then the previous posts address that quite well.
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« Reply #6 on: November 02, 2015, 06:03:03 PM »
satz flying
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1. Rebind the rx and tx
2. Added toroid to servo wire.

Still facing the problem.look at the video
http://1drv.ms/1GHEzMX

Need to try other methods

And no jitter if remove horns from servo.
« Last Edit: November 02, 2015, 09:06:23 PM by satz flying » Logged

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