Gs 540 Flutter Problems
 

i 'am having problems with my gs 540 , the elevator flutters in knife edge attitude. the hinge's are all sealed, and i can't find any slop in the linkages the servo's are new hs 225's mg. what could be possibley be causing this ? i would apreciate any help!
Chad

Gs 540 Flutter Problems
 

Don't despair, there's something causing it. Can you post a pic of the linkage so we can see the setup?

Thanks,

JW

Gs 540 Flutter Problems
 

Is it taking alot of speed to hold knife edge ? You have 2-225's on the elevator ? All I can figure if you've checked all the obvious is that your airspeed is too high, but that doesn't help much..not like you can slow it down if it won't hold knife edge. Maybe a higher torque servo would be in order. Nothing like throwing money at a problem. :D One other option might be braces or flying wire on the tail...the whole stab might be oscillating and not just the elevator.

Gs 540 Flutter Problems
 

hear are the pics , it has 2 hs 225's on the elevator. running on 6 volts= 67oz.

Gs 540 Flutter Problems
 

it does take a little more speed to keep it on knife edge. but it will fly level at the same throtlle setting and not flutter.

Gs 540 Flutter Problems
 

Try moving the clevis to the outer most hole on the control horn. Hopefully this will solve your problem.

Andy

Gs 540 Flutter Problems
 

What size plane is that ?
I'd bet money your control rod is flexing. Almost looks like 2-56 in the picture. If so, I'd go with 4-40's and ball links for connectors. Just a thought.

Gs 540 Flutter Problems
 

they are 4-40 rods, on a 80" wing fun fly, there is another guy at our club with the same plane and same set up and his doesnt flutter.

another thing is you can also see the elevator surface flutter in a hover, that is really stange to me , it doesnt do it much in a hover but you can see it from time to time.

the flying wires are an interesting thought !!!! maybe the whole surface is oscilating , how do figure out if it is ????

thanks
Chad

Gs 540 Flutter Problems
 

if i move the clevis out i will lose alot of throw, doesnt 3d well with less throw. however this may solve the problem. i really want to keep all the throw i have now because i was actually looking for some more!!!!

thanks
Chad

Gs 540 Flutter Problems
 

I understand your problem. The only other option I can give you is to replace the plastic servo arms (looks like dubro h.d. arms) and get some aluminum ones and use ball links. I wouldn't use ball links on the control surface due possibility of control arm flexing under heavy 3D loads.

Try it, it might work.

Andy

Gs 540 Flutter Problems
 

Normally it's hard to actually see the stab fluttering. It'll usually transfer it's oscillation to the weakest link..being the elevator.
Bracing is a good option, but I'd hate to see you drill holes and what not in your stab for anchors and discover it didn't help.
4-40's look small on a big bird aye ? ;)
I would still seriously think about ball links instead of z-bends at the servo arm. It'd be an easy fix. They may feel snug but the extra precision in a ball link might just be enough to eliminate the flutter. What servos does the guy have you mentioned ?

Gs 540 Flutter Problems
 

he has futaba 9002 or some 9000 number not real sure wich one but i think he said that they have around 70oz of torque so about the same as mine.

i have never fooled with ball link conectors, this is just my secound big plane. so i'am pretty new to all this bigger stuff so i'am leaning as i go. where do i get the ball link connectors?

i really apreciate your all's input :D

thanks
Chad

Gs 540 Flutter Problems
 

Dubro makes a good set. I've got 4-40's and ball links on my big gasser. Tower or your local hobby store should have them. You'll just need to get 4-40 rod threaded at both ends, the right length. Might only be able to find a full length thread. I have a 4-40 die but quickly found that your can't run threads on 4-40 sized rods. The ball links won't fit...grrrr. The threaded rod you buy at the hobby store has rolled threads which are just a tad bigger in diameter. Anyway, that's what I'd do. Also, I run hitecs in a lot of my stuff and I've been happy with them, BUT I'd say the futaba's have less slop around center which is really critical when you'r talking speed and 3D type control surfaces. I'd try the ball links first, if that doesn't work-either brace the tail or drop some coin on some higher end servos.

Gs 540 Flutter Problems
 

I disagree with the full length threaded rod for push rods. That stuff is to flexible and will cause flutter. I buy the 4-40 rods that are threaded on one end. Great planes makes a solder thread for 4-40 rods. All you have to do is put your ball link on one end, measure and cut the rod off at the non-threaded end. Now scuff up the rod and I take a triangle metal file and file a couple of shallow grooves in the rod and then solder the 4-40 end onto it. I've never had one fail this way. This is much stronger than all thread and looks good. You can always make your rods from carbon fiber tubes, but not really necessary. I've got the above mentioned rods on a 36% edge 540 and have never had a problem.

Andy

Gs 540 Flutter Problems
 

If it's an ARF check the tail construction. Flew my Model Tech SU-29 ARF Sunday (probably had 50 flights on it) and put it into a 90 degree left bank to enter a knife edge pass. Heard about two seconds of flutter (never fluttered before) and before I could cut the throttle the tail blew off. Pretty impressive actually, the vertical and horizontal surfaces came off in about five pieces and fluttered to the ground while the rest of the plane went into a nice spin that I could actually slow down with the ailerons. It hit the ground fairly slow so the damage was minimal (didn't even break the prop). When I looked at the mounting surface for the tail surfaces on the fuse the glue had only been applied to two small areas front and rear (about 10% of the mounting area). Didn't like the tail anyway.

Mike

Gs 540 Flutter Problems
 

Cooney, are you running 6 volts? I'm just checking - I realize you are an experienced flyer and you probably know that the 225 doesn't have enough torque for an 80" with standard voltage.
Just checking.

Gs 540 Flutter Problems
 

For diagnostic purposes, move the clevis out to the farthest hole on the control horn. There is a possibility that the setup ie. servo arm / and servo that you are using, coupled with the inward hole on the control horn, could be the culpret. You are fine with a Z bend and a straight shot with a clevis (like you have). I know it isn't what ball link fans want to hear, but ball links can cause flutter by twisting the control horn. Many flyers only use them on throttle because of this. If you feel comfortable to fly it after the linkage adjustment, let me know and we'll go from there. If not, I suggest a larger servo. I'm almost done framing a GSE540 now.

Gs 540 Flutter Problems
 

I would be concerned that the 225 would be on the verge of being too small on a plane this size with 3D throws, even at 6V. An elevator that size at 45 degrees of throw requires some substantial holding power. It may be too much for the little Hitec mini. If you have zero slop in your linkages and they are not flexing, you have the linkages setup properly mechanically and electronically if using a computer radio, used enough hinges, and the hinge line is sealed, then I would suspect the servos.

Gs 540 Flutter Problems
 

I just looked at the photo you posted. I think Flyingdoc may be right. You definitely have the rod inboard on your control horn. I'd try putting it in the last hole outboard as Flyingdoc suggested. I doubt this servo could deal with a mechanical disadvantage like that. Just a thought.

Gs 540 Flutter Problems
 

yes i'am running 6 volts. and i believe the little servos are doing the job. it will do the wall like no other plane i ever had. it never lacks for elevator right now. and i have them on the rudder also it has awesome rudder response. i know the servo's are on the low end but there is 2 of them on both surfaces. putting the total on the 135oz range on the surface. mike from ohio model planes claims he did this (2 servo's per half) so that you can run a mid grade servo. which i consider a 225 a mid grade servo. am i wrong in thinking this? i came out at 12lbs all up flying weight by using the mighty mini.

i was talking to one the veteran club members today about the problem and mentioned to him about the flying wires and he agreed that it could be oscillation of the tail. since you can kinda notice it in hover every once in a while. i think i'll move the clevis out on the control horn a few notches and add the flying wires they look good any ways so even of they don't help i will still like them.
if that don't fix it then i'll try the ball link. but there is really no slop in the linkage now. maybe some carbon fiber rods with ball links if all else fails!!!! :confused:

thanks for all the input guys :D it really helps

Chad

Gs 540 Flutter Problems
 

I would change servos...see if you can find someone to let you try a couple higher end servos and see if it fixes the problem......i had 2-225mg's on the v-tail of my pilon plane with a ttpro40 and lost the plane due to the servo's......i had one crap out on me and since i just bought them my LHS just swapped them out for me for the same servo....when i flew it again another servo went out and i lost the plane....not saying 225's are prone to failure and definately not bashing but i wouldnt trust another plane to these servos.....just my .02

P.S. Im still running 925mg's on my chopper with no problems....so im not bashing hi-tech

Gs 540 Flutter Problems
 

Dynamic balancing of the stab will help control flutter also.

Gs 540 Flutter Problems
 

now that is interesting , how does one properly balnce them ???

Chad

Gs 540 Flutter Problems
 

yes , i would not try these servo's on a pylon plane either there is just much speed involved, the more speed you have the more torque you need, however this planes top speed might be 80 mph on a good down leg :D . this is a funfly and flys very slow not like scale edge 540. plus i would have to rebuild the tail section of the fuse to install bigger servos :( . however if i can not fix the problem i will have to rebuild :( .
thanks for the input and i hope the servo's hold up for me, i know they are on the low end for this aplication but they seem to hold very good in all other flight attitiude other than knife edge :confused: .

thanks
Chad

my tail pictures as promised
 

Here are the pictures of my set-up that works very well. By the way what engine do you have in it? I dont think I have seen that yet. I am running the saito 180 on 30% morgans fuel. Awsome hovers and rolling herriers!!!!!