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<DIV>John,</DIV>
<DIV> </DIV>
<DIV>its likely a worn pot.</DIV>
<DIV> </DIV>
<DIV>The 8411 and 8411SA will tend to be a little less tolerant of a poor
linkage setup on rudder. What can happen is a spongy rudder cable setup, and the
servos are extremely precise so they will try to fight their way to center. The
result of the spongy cable setup will cause it to over shoot each time and it
will with a little vibration and pot wear cause the servo fight itself.
</DIV>
<DIV> </DIV>
<DIV>The rule of thumb on these if you can put your hand on it and it stops then
air loads will not allow it bounce while in flight. Now I personally look at it
as an opportunity to be thinking of a servo change. I don't immediately change
it out, but it goes on the list of things to do. I may fly it until next week
when I check the other servos but I probably don't put 50 flights on it this
way. </DIV>
<DIV> </DIV>
<DIV>This is a dead band thing. A price that you may pay for a very accurate and
precise servo. Now it is my understanding the 8311 is an 8411SA that has an
upgraded motor and the deadband is adjusted a bit wider for the Heli guys so the
servos don't tend keep fighting for center as hard. We are talking about small
changes but they will affect the results. I have heard from guys that use the
8311 in place of the 8411SA and they tell me that the pot wear shows less with
this servo. You may want to talk to Eric Henderson. Last I knew he was running
these servos 2 years ago. I don't know for sure, Eric seems to have dropped off
the map. I know he was moving and such but I haven't heard from him since about
Thanksgiving. Eric has some experience with these servos. Another source would
be Dave Lockhart, he is always playing with servos, and probably has used the
8311's. </DIV>
<DIV> </DIV>
<DIV>I switched to 8611's on the rudder a few years ago. Its way overkill for
sure but I have not had any servo wear issues since I installed the beast in
there. I run my cables on the rudder pretty tight. As in Willie Nelson
could use them for guitar strings. The setup I use is a extremely tight rudder
response with no spongy feeling. It will make you re-evaluate your rudder
deflections and expo settings as the rudder is as tight as the ailerons or
elevator.</DIV>
<DIV> </DIV>
<DIV>This spongy setup is a cause of the bouncing, but there are others as well.
Sometimes a longer control horn on the rudder will make a huge difference. I
tend to run pretty long rudder horns on the rudder side. Most guys I see put the
link close to the rudder and then have little mechanical advantage. They are
trying to get a 1-1 ratio servo arm to rudder horn. You don't want that. That
will maximize any errors in the linkage or servo pot and gear wear.
</DIV>
<DIV> </DIV>
<DIV>Another thing I have seen is the heavier rudders will be more affected.
There was an Alliance that was built by a friend. He'll remain nameless, but he
used triangle stock on the LE of the Rudder to get a good bevel. The problem was
he made the rudder normally and then added the tri-stock on top original LE
facing. This added a bit of weight to the rudder and also it changed the size of
the surface about 1/2-3/4" more chord. The model then got sold through a couple
of friends and that beast was hell on Rudder servos. I mean it would eat any
servo in about 50 flights. Well cut the bad boy off, bevel it correctly, and
hinge it a little better than it was and the model went 250 flights on the same
servo that was showing signs of the bounce after about 30-40 flights. It was an
extreme case and something about that plane, that rudder, and that
setup gave some kind of a harmonic. </DIV>
<DIV> </DIV>
<DIV>If you continue to have the problem look to change the setup and it will
likely solve your issue. Look to control horn length. Most guys use a 6-32 bolt.
Replace it with a longer one. My rudder horns are about 1.25" from the
rudder hinge line. Another help is to Bend the bolt so the pivot point is
over the hinge line. Adjust the servo arm side of things. Make sure you are
getting good mechanical advantage over the rudder. If this doesn't help look to
change the mass of the rudder. Cut holes in it and recover it. Do something to
change the dynamics. </DIV>
<DIV> </DIV>
<DIV>The 8411SA and hence the 8311 is an awesome servo for just about any
pattern application, ailerons, elevator, or rudder. Its super strong, fairly
fast, and is great in the precision which beats out the other two specs hands
down. What you have is a servo that is being precise but the system its used in
has a property that is causing it to over work itself.</DIV>
<DIV> </DIV>
<DIV>Hope this helps</DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV>Troy Newman</DIV>
<BLOCKQUOTE
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=jpavlick@idseng.com href="mailto:jpavlick@idseng.com">John
Pavlick</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=nsrca-discussion@lists.nsrca.org
href="mailto:nsrca-discussion@lists.nsrca.org">NSRCA Mailing List</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Thursday, April 26, 2007 9:26
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [NSRCA-discussion] JR servo
question</DIV>
<DIV><BR></DIV>
<DIV>Yeah, that sounds like what I remember hearing about but I couldn't
remember exactly which servos behaved that way. I think my
problem may just be a worn pot as a few guys have suggested. As long as I know
there's not something going on with this specific servo (as was the case with
your 8411's) I'll just have it rebuilt. I replaced it with a spare servo for
now and everything is working fine again. Hoping for some good weather on
Sunday so I can get some practice time in.</DIV>
<DIV> </DIV>
<DIV>John Pavlick<BR><A
href="http://www.idseng.com">http://www.idseng.com</A></DIV>
<BLOCKQUOTE
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=JonLowe@aol.com href="mailto:JonLowe@aol.com">JonLowe@aol.com</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=nsrca-discussion@lists.nsrca.org
href="mailto:nsrca-discussion@lists.nsrca.org">nsrca-discussion@lists.nsrca.org</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Thursday, April 26, 2007 11:35
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [NSRCA-discussion] JR
servo question</DIV>
<DIV><BR></DIV>
<DIV>
<DIV>
<DIV>In a message dated 4/26/2007 8:10:39 PM Central Daylight Time, <A
href="mailto:jpavlick@idseng.com">jpavlick@idseng.com</A> writes:</DIV>
<BLOCKQUOTE
style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: blue 2px solid">
<DIV><FONT face=Arial size=2>Since I'm a Futaba user, I'll try to be nice
about this. <VBG> I have an airplane set up with JR servos and
I'm experiencing the classic "oscillating rudder" issue. There's a JR 8311
servo on the rudder and the cables aren't excessively tight. I remember
hearing about this a while ago but I can't remember the solution. Any help
would be appreciated.</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial size=2>John Pavlick</FONT></DIV></BLOCKQUOTE></DIV>
<DIV>John,</DIV>
<DIV>I don't know about 8311s, but I've had two 8411s do it, one brand
new. Some suggested an oring around the two pull pull cables, to apply
a very slight drag.. I cured mine by going to an 8611. Something
in the 8411s is too tight in the feedback loop I guess.</DIV></DIV>
<DIV> </DIV>
<DIV><FONT size=2 PTSIZE="10">Jon Lowe<BR></FONT></DIV><BR><BR><BR>
<DIV><FONT style="FONT: 10pt ARIAL, SAN-SERIF; COLOR: black">
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