[NSRCA-discussion] Servo question

[Paul LaChance]

I also remember regular maintenance involoved re-lubing the pots.  Used to 
get pot lube that was in a little capsule like a pill capsure.  LOL  Man we 
had to work hard those days to keep stuff working.

Paul
----- Original Message ----- 
From: "Ron Van Putte" <vanputte at cox.net>
To: "General pattern discussion" <nsrca-discussion at lists.nsrca.org>
Sent: Saturday, July 05, 2008 7:57 PM
Subject: Re: [NSRCA-discussion] Servo question


> And the Giezendanner special pot wipers we imported from Switzerland  to 
> make them last longer.  I long for those good old times NOT.
>
> Ron VP
>
> On Jul 5, 2008, at 6:44 PM, <glmiller3 at suddenlink.net> wrote:
>
>> Ah, Jon,
>>
>> I remember changing my servo pots every 30-50 flights as a routine 
>> maintenance procedure....with the old Kraft Signature set.<G>
>>
>> G
>> ---- Jon Lowe <jonlowe at aol.com> wrote:
>>
>> =============
>>
>>  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.
>>
>> 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.
>>
>>
>>
>>
>>
>> Jon Lowe
>>
>>
>>
>>
>>
>>
>> -----Original Message-----
>> From: chris moon <cjm767driver at hotmail.com>
>> To: nsrca-discussion at lists.nsrca.org
>> Sent: Sat, 5 Jul 2008 12:47 pm
>> Subject: [NSRCA-discussion] Servo question
>>
>>
>>
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>>
>>
>> Ok, here is a brain teaser for you experts.
>>
>> On Sunday 2 weeks ago I went out flying maybe 4-5 flights. All was
>> fine.  When I got to the flying site on Friday for the Lake City
>> contest, I made a practice flight and the plane was climbing like mad.
>> I got it down and found that 1 of the elevator halves was about  3/8" up
>> from the other.  Before the flight, I checked the operation of the
>> elevators and they were moving correctly but I don't remember
>> specifically if I paid any attention to if they were centered
>> perfectly.  Now, nothing was changed between the the last time I flew
>> and this flight.  The transmitter was on the right model.  The linkage
>> had not slipped, nor had the control horn bent.  The control surface
>> showed no sign of trauma from a severe bump possibly causing a  stripped
>> gear.  The servo (JR 3421sa) was functioning 100% normally it was just
>> the center had changed on it's own.  I removed the servo arm (alum  - not
>> stripped either) and moved it one spline and adjusted the sub trim
>> slightly and flew a few test flights and the contest with no problems.
>> Now at home, I removed the servo to send it back and inspected it and
>> found nothing abnormal.  The gears all look fine. Here is what I have
>> eliminated:
>>
>> servo arm - not stripped
>> servo gears - not stripped
>> pushrod and linkage - no play and not slipped on the clevis threads
>> transmitter - correct model selected and could not be elevator pot in
>> transmitter since it did not affect the other elevator servo's  centering
>>
>> I am sending it back for a check up but just was wondering if  anyone has
>> had any similar experience ever or if they have any possible causes.
>>
>> Thanks
>>
>> Chris
>>
>>
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>>
>> Making the world a better place one message at a time. Check out  the i'm 
>> Talkathon.=
>>
>>
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>>
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