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<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=734053115-22052008><STRONG>See answers below:</STRONG></SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial size=2><SPAN
class=734053115-22052008></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT face=Arial size=2><SPAN class=734053115-22052008>
<DIV><SPAN class=611385614-22052008><FONT face="Berlin Sans FB">There was some
of the typical RC discussion at Hemet - and one topic that came up, as it
usually does, is servo wear and replacement. With today's digital servos, I have
the following questions about digital servo replacement;</FONT></SPAN></DIV>
<DIV><SPAN class=611385614-22052008><FONT
face="Berlin Sans FB"></FONT></SPAN> </DIV>
<DIV><SPAN class=611385614-22052008><FONT face="Berlin Sans FB">1) what are the
symptoms of a digital servo that is starting to wear out?</FONT></SPAN></DIV>
<DIV><SPAN class=611385614-22052008> <FONT
face="Berlin Sans FB">- poor centering ? </FONT><FONT face=Arial
size=2><SPAN class=734053115-22052008> <FONT face="Berlin Sans FB"><FONT
size=3> <FONT
color=#0000ff>YES</FONT></FONT></FONT> </SPAN></FONT></SPAN></DIV>
<DIV><SPAN class=611385614-22052008><FONT face="Berlin Sans FB" color=#0000ff
size=3><SPAN class=734053115-22052008></SPAN></FONT></SPAN> </DIV>
<DIV><SPAN class=611385614-22052008><FONT face="Berlin Sans FB" color=#0000ff
size=3><SPAN class=734053115-22052008></SPAN></FONT></SPAN> </DIV>
<DIV><SPAN class=611385614-22052008>
<FONT face="Berlin Sans FB">- does this equate to a louder 'buzz' at
center</FONT><FONT face=Arial size=2><SPAN class=734053115-22052008> <FONT
face="Berlin Sans FB" size=3>, <FONT color=#0000ff>NO Less buzz. The pot is worn
and the servo think its at center so it doesn't try to drive to
center.</FONT></FONT></SPAN></FONT></SPAN></DIV>
<DIV><SPAN class=611385614-22052008><FONT face=Arial color=#0000ff size=2><SPAN
class=734053115-22052008></SPAN></FONT></SPAN> </DIV>
<DIV><SPAN class=611385614-22052008>
<FONT face="Berlin Sans FB">- is the only way to tell this to put a servo on
some sort of protractor and look at the centering?</FONT><FONT face=Arial
size=2><SPAN class=734053115-22052008> <FONT face="Berlin Sans FB"
size=3> <FONT color=#0000ff>NO run the Servo test feature in your TX. If
your radio doesn't have one then get a JR MatchMaker device about $20. You
can plug the servo into it and cycle the servo at various speeds. You will see
hesitations and stopping at center with a worn pot. This is where the servo
spends most of its time and vibes will wear on the pot at this "center point". A
protractor device can help you see it, but if its bad enough to need replacing
you can see it with your naked eye. The servo will stop at center as it passes
through. A new servo will just pass right through at the same speed with zero
hesitation and no speed change.</FONT></FONT></SPAN></FONT></SPAN></DIV>
<DIV><SPAN class=611385614-22052008><FONT face=Arial color=#0000ff size=2><SPAN
class=734053115-22052008></SPAN></FONT></SPAN> </DIV>
<DIV><SPAN class=611385614-22052008>
<FONT face="Berlin Sans FB">- does thee servo draw more current?</FONT><FONT
face=Arial size=2><SPAN class=734053115-22052008> <FONT
face="Berlin Sans FB" size=3> <FONT color=#0000ff>No they draw less
current. The way a servo works is the servo sees its position and it sees
the commanded position to go to. This information is given to the servo by a
feedback pot. A small potentiometer in the servo that is attached to the output
gear. If the servo is already there very little juice is required to maintain
this position. As loads increase on the flight surfaces like sitting on the
ground the weight of the aileron will create a load that is trying to move the
servo off its commanded position. So you get the buzz. The servo is giving power
to drive back tot he commanded location. Digital servos sample this pot position
like 5 times more often than an analog servo. Each time the position is sampled
a small little jolt of power is applied to drive the servo back to its commanded
location. This is why digital servos offer better holding power and
centering. They tell the servo to go to its commanded position more often,
and have less deadband in the middle where it says that as close as I can
get it. If the servo pot is worn then the servo thinks that a wide area in
the worn spot on the pot is good it then stops trying to drive the servo to
the commanded position. It gets it close and thinks its there. This problem Goes
back to the poor centering.</FONT></FONT><FONT color=#0000ff> <FONT
face="Berlin Sans FB" size=3> So it stops 0.1deg short or goes 0.05degs
long. As the pot wear gets worse the dead spot gets larger and the error
gets more. Yet the servo still thinks its at the commanded location. This is not
servo deadband...but the worn pot can play havoc with the servo and its
deadband.</FONT></FONT></SPAN></FONT></SPAN></DIV>
<DIV><SPAN class=611385614-22052008><FONT
color=#0000ff></FONT></SPAN> </DIV>
<DIV><SPAN class=611385614-22052008><FONT face="Berlin Sans FB">2) What tests
can be performed either 'in the plane' or 'outside the plane' to determine if a
servo needs to be replaced?</FONT></SPAN></DIV>
<DIV><SPAN class=611385614-22052008> <FONT
face="Berlin Sans FB">- In plane testing would be ideal, but we must compare
against a 'new' servo, so maybe this is not practical.</FONT><FONT face=Arial
size=2><SPAN class=734053115-22052008> </SPAN></FONT></SPAN></DIV>
<DIV><SPAN class=611385614-22052008><FONT face=Arial size=2><SPAN
class=734053115-22052008></SPAN></FONT></SPAN> </DIV>
<DIV><SPAN class=611385614-22052008><FONT face=Arial size=2><SPAN
class=734053115-22052008><FONT face="Berlin Sans FB" color=#0000ff size=3>The
servos can be tested inside the plane...A pointer or throw meter device can be
used to see the servo slow or hesitate at center. Using the servo monitor and
the servo test function in your TX the servos will cycle slowly
and you can see the hesitations. The MatchMaker device is a servo tester
and servo driver. It works very well for this function.
</FONT></SPAN></FONT></SPAN></DIV>
<DIV><SPAN class=611385614-22052008><FONT face=Arial size=2><SPAN
class=734053115-22052008></SPAN></FONT></SPAN> </DIV>
<DIV><SPAN class=611385614-22052008><FONT face=Arial size=2><SPAN
class=734053115-22052008></SPAN></FONT></SPAN> </DIV>
<DIV><SPAN class=611385614-22052008><FONT face=Arial size=2><SPAN
class=734053115-22052008><FONT color=#0000ff><FONT face="Berlin Sans FB"
size=3>Tony Frakowiak taught me that when the servos start to fade away the
model will not lock on nearly as well. I didn't believe him until I flew the
model both ways. It can make a huge difference.</FONT> <FONT
face="Berlin Sans FB" size=3> Another thing is that as the pots wear the end
point adjustments will wander. So your models TX setup will change over time.
Aileron differential can suffer and even mixing value will suffer as the models
usually have small percentages of mix. The servos are trying to operate in the
"worn spot" Where I see the biggest problem is on 4/8pt roll elements they are
just not crisp and clean.</FONT></FONT></SPAN></FONT></SPAN></DIV>
<DIV><SPAN class=611385614-22052008><FONT face="Berlin Sans FB" color=#0000ff
size=3><SPAN class=734053115-22052008></SPAN></FONT></SPAN> </DIV>
<DIV><SPAN class=611385614-22052008><FONT face="Berlin Sans FB" color=#0000ff
size=3><SPAN class=734053115-22052008>yes even the Flower powered models will
suffer from this problem. There is vibration, it may not be as bad as the Glow
powered models but it is still there and the pots and servos will wear. I flew
Electric for a year and still saw servo changes with
time.</SPAN></FONT></SPAN></DIV>
<DIV><SPAN class=611385614-22052008><FONT face="Berlin Sans FB" color=#0000ff
size=3><SPAN class=734053115-22052008></SPAN></FONT></SPAN> </DIV>
<DIV><SPAN class=611385614-22052008><FONT face="Berlin Sans FB" color=#0000ff
size=3><SPAN class=734053115-22052008>Another factor is the gear trains will
wear a little. Metal gears much worse than nylon. As the gear trains wear the
servos will fight to get to commanded location and the gear slop will constantly
over shoot to commanded location. So the servo will get more pot wear and it can
use more current in this situation. The constant overshoot will have the servo
fighting itself. This can also happen with the worn pots. Turn on the model and
one surface just constantly oscillates. You either have a problem with your
linkages or the servo is worn. By the way its common with poor rudder cable
setups to get this problem on rudder servo in just a few flights. This is
usually not the servos fault but operator error and his cable setup is not good.
A poor pull pull setup can literally eat a rudder servo
alive.</SPAN></FONT></SPAN></DIV>
<DIV><SPAN class=611385614-22052008><FONT face="Berlin Sans FB" color=#0000ff
size=3><SPAN class=734053115-22052008></SPAN></FONT></SPAN> </DIV>
<DIV><SPAN class=611385614-22052008><FONT face="Berlin Sans FB" color=#0000ff
size=3><SPAN class=734053115-22052008>This is a reason to use the JR "SA" servos
these servos have nylon gears and perform better in the vibration
situations.</SPAN></FONT></SPAN></DIV>
<DIV><SPAN class=611385614-22052008><FONT face="Berlin Sans FB" color=#0000ff
size=3><SPAN class=734053115-22052008></SPAN></FONT></SPAN> </DIV>
<DIV><SPAN class=611385614-22052008><FONT face="Berlin Sans FB" color=#0000ff
size=3><SPAN class=734053115-22052008>Horizon Hobby can replace the gears and
pots for you. Its usually a fee of under $20 depending on which servo it is.
When you consider a $100 servo the fee to make it like new again is small.
</SPAN></FONT></SPAN></DIV>
<DIV><SPAN class=611385614-22052008><FONT face="Berlin Sans FB" color=#0000ff
size=3><SPAN class=734053115-22052008></SPAN></FONT></SPAN> </DIV>
<DIV><SPAN class=611385614-22052008><FONT face="Berlin Sans FB" color=#0000ff
size=3><SPAN class=734053115-22052008>Troy Newman</SPAN></FONT></SPAN></DIV>
<DIV><SPAN class=611385614-22052008><FONT face="Berlin Sans FB" color=#0000ff
size=3><SPAN class=734053115-22052008>Team
JR</SPAN></FONT></SPAN></DIV></SPAN></FONT></DIV><BR>
<DIV class=OutlookMessageHeader lang=en-us dir=ltr align=left>
<HR tabIndex=-1>
<FONT face=Tahoma size=2><B>From:</B> nsrca-dist7-bounces@lists.nsrca.org
[mailto:nsrca-dist7-bounces@lists.nsrca.org] <B>On Behalf Of
</B>Scott<BR><B>Sent:</B> Thursday, May 22, 2008 8:05 AM<BR><B>To:</B>
dist7@nsrca.org<BR><B>Subject:</B> [NSRCA-dist7] Servo replacement / wear - how
to tell<BR></FONT><BR></DIV>
<DIV></DIV>
<DIV><SPAN class=611385614-22052008><FONT face="Berlin Sans FB">
<DIV><SPAN class=611385614-22052008><FONT face="Berlin Sans FB">There was some
of the typical RC discussion at Hemet - and one topic that came up, as it
usually does, is servo wear and replacement. With today's digital servos, I have
the following questions about digital servo replacement;</FONT></SPAN></DIV>
<DIV><SPAN class=611385614-22052008><FONT
face="Berlin Sans FB"></FONT></SPAN> </DIV>
<DIV><SPAN class=611385614-22052008><FONT face="Berlin Sans FB">1) what are the
symptoms of a digital servo that is starting to wear out?</FONT></SPAN></DIV>
<DIV><SPAN class=611385614-22052008> <FONT
face="Berlin Sans FB">- poor centering ? </FONT></SPAN></DIV>
<DIV><SPAN class=611385614-22052008>
<FONT face="Berlin Sans FB">- does this equate to a louder 'buzz' at
center</FONT></SPAN></DIV>
<DIV><SPAN class=611385614-22052008>
<FONT face="Berlin Sans FB">- is the only way to tell this to put a servo on
some sort of protractor and look at the centering?</FONT></SPAN></DIV>
<DIV><SPAN class=611385614-22052008>
<FONT face="Berlin Sans FB">- does thee servo draw more
current?</FONT></SPAN></DIV>
<DIV><SPAN class=611385614-22052008></SPAN> </DIV>
<DIV><SPAN class=611385614-22052008><FONT face="Berlin Sans FB">2) What tests
can be performed either 'in the plane' or 'outside the plane' to determine if a
servo needs to be replaced?</FONT></SPAN></DIV>
<DIV><SPAN class=611385614-22052008> <FONT
face="Berlin Sans FB">- In plane testing would be ideal, but we must compare
against a 'new' servo, so maybe this is not practical.</FONT></SPAN></DIV>
<DIV><SPAN class=611385614-22052008><FONT
face="Berlin Sans FB"></FONT></SPAN> </DIV>
<DIV><SPAN class=611385614-22052008><FONT face="Berlin Sans FB">Any thoughts on
the above would be considered.</FONT></SPAN></DIV>
<DIV><SPAN class=611385614-22052008><FONT
face="Berlin Sans FB"></FONT></SPAN> </DIV>
<DIV><SPAN class=611385614-22052008><FONT
face="Berlin Sans FB">Thanks</FONT></SPAN></DIV>
<DIV><SPAN class=611385614-22052008><FONT
face="Berlin Sans FB"></FONT></SPAN> </DIV>
<DIV><SPAN class=611385614-22052008><FONT
face="Berlin Sans FB">sc</FONT></SPAN></DIV>
<DIV><SPAN class=611385614-22052008><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV></FONT></SPAN><SPAN
class=611385614-22052008><FONT
face="Berlin Sans FB"></FONT></SPAN></DIV></BODY></HTML>