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Jon:<br>
<br>
Thanks for the great info. Never knew that one. I looked in there and
saw the slot you mentioned. I'll leave it up to Horizon to figure out
why it changed all of a sudden.<br>
<br>
Chris<br>
<br>
Jon Lowe wrote:
<blockquote
cite="mid:8CAACE7CE719113-CAC-607A@webmail-de08.sysops.aol.com"
type="cite">
<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;">Jon Lowe</div>
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-----Original Message-----<br>
From: chris moon <cjm767driver@hotmail.com><br>
To: <a class="moz-txt-link-abbreviated" href="mailto:nsrca-discussion@lists.nsrca.org">nsrca-discussion@lists.nsrca.org</a><br>
Sent: Sat, 5 Jul 2008 12:47 pm<br>
Subject: [NSRCA-discussion] Servo question<br>
<br>
</cjm767driver@hotmail.com>
<div id="AOLMsgPart_3_6d6b51bf-7e60-404a-b7ed-ead326f954d9">
<style>#AOLMsgPart_3_6d6b51bf-7e60-404a-b7ed-ead326f954d9 .hmmessage P{margin:0px;padding:0px}#AOLMsgPart_3_6d6b51bf-7e60-404a-b7ed-ead326f954d9 body.hmmessage{FONT-SIZE: 10pt;FONT-FAMILY:Tahoma}</style>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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