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<DIV><FONT face=Arial size=2>Jon</FONT></DIV>
<DIV><FONT face=Arial size=2>I have some #4721 & #4131 are the pots adjusted
the same as the #3421's?</FONT></DIV>
<DIV><FONT face=Arial size=2>Bill T.</FONT></DIV>
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<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">Jon Lowe</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> Saturday, July 05, 2008 2:55
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [NSRCA-discussion] Servo
question</DIV>
<DIV><BR></DIV>
<DIV><FONT face="Arial, Helvetica, sans-serif">3421's have the pot shaft
driven directly by the output shaft. If you reach down thru the hole for
the servo arm screw with a jewelers screwdriver, there is a slot that can be
used to adjust centering of the pot which is a press fit into the gear.
The pot shaft may have slipped in the output gear. Pot shaft could be
binding, or the output gear may be cracked internally allowing the shaft to
slip. You could just need a new output gear. I'd try adjusting it to see
how easy it slips. A VERY small movement of the pot shaft will affect
centering in a BIG way, so be careful. Perhaps, the pot may also be
coming apart or wearing badly internally, affecting centering.
Definitely determine the cause or send it back to have at least the pot
replaced, along with the gears.<BR><BR>Years ago, many servo pots were driven
like this, and didn't caouse a problem except for servo pot wear.
Replacing pots after 25 flights was not all that uncommon. Most (all)
larger servo pots anymore are indirect drive to help prevent pot wear.
3421 is probably just too small to do an indirect drive.<BR></FONT></DIV>
<DIV><BR></DIV>
<DIV id=sig7585 style="CLEAR: both"><FONT size=+0>Jon Lowe</FONT></DIV>
<DIV><BR></DIV>
<DIV><BR></DIV>-----Original Message-----<BR>From: chris moon
<cjm767driver@hotmail.com><BR>To:
nsrca-discussion@lists.nsrca.org<BR>Sent: Sat, 5 Jul 2008 12:47 pm<BR>Subject:
[NSRCA-discussion] Servo question<BR><BR>
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Ok, here is a brain teaser for you experts.<BR><BR>On Sunday 2 weeks ago I
went out flying maybe 4-5 flights. All was <BR>fine. When I got to the flying
site on Friday for the Lake City <BR>contest, I made a practice flight and the
plane was climbing like mad. <BR>I got it down and found that 1 of the
elevator halves was about 3/8" up <BR>from the other. Before the flight, I
checked the operation of the <BR>elevators and they were moving correctly but
I don't remember <BR>specifically if I paid any attention to if they were
centered <BR>perfectly. Now, nothing was changed between the the last time I
flew <BR>and this flight. The transmitter was on the right model. The linkage
<BR>had not slipped, nor had the control horn bent. The control surface
<BR>showed no sign of trauma from a severe bump possibly causing a stripped
<BR>gear. The servo (JR 3421sa) was functioning 100% normally it was just
<BR>the center had changed on it's own. I removed the servo arm (alum - not
<BR>stripped either) and moved it one spline and adjusted the sub trim
<BR>slightly and flew a few test flights and the contest with no problems.
<BR>Now at home, I removed the servo to send it back and inspected it and
<BR>found nothing abnormal. The gears all look fine. Here is what I have
<BR>eliminated:<BR><BR>servo arm - not stripped<BR>servo gears - not
stripped<BR>pushrod and linkage - no play and not slipped on the clevis
threads<BR>transmitter - correct model selected and could not be elevator pot
in <BR>transmitter since it did not affect the other elevator servo's
centering<BR><BR>I am sending it back for a check up but just was wondering if
anyone has <BR>had any similar experience ever or if they have any possible
causes.<BR><BR>Thanks<BR><BR>Chris<BR><BR><BR><BR><BR><BR>
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