[NSRCA-discussion] Servo question

[glmiller3 at suddenlink.net]

Yeah, Ron,

Were those the ones with a little piece of carbon at the wiper tip?  I remember that now!

G
---- Ron Van Putte <vanputte at cox.net> wrote: 

=============
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
>
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>
>
> -----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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>
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