[NSRCA-discussion] DS 8411sa Servo Oscillation on Rudder

[Ed Alt]

Jim:
Yeah, it's the opposite of escapement  what should we call it?  Actually, a 
few years ago, a Horizon rep mentioned the rubber band thing on Doug's Scale 
Aerobatics list and got a lot of flack for it.  Never thought I would see 
that suggesion raised again!

Ed


>From: "Jim Woodward" <jim.woodward at schroth.com>
>Reply-To: NSRCA Mailing List <nsrca-discussion at lists.nsrca.org>
>To: "'NSRCA Mailing List'" <nsrca-discussion at lists.nsrca.org>
>Subject: Re: [NSRCA-discussion] DS 8411sa Servo Oscillation on Rudder
>Date: Thu, 24 Aug 2006 12:28:09 -0400
>
>I get a kick out of these threads about installing new JR gear sets, and we
>can now add, using rubberbands on them. :)
>
>Jim W.
>Team Futaba
>
>
>
>-----Original Message-----
>From: nsrca-discussion-bounces at lists.nsrca.org
>[mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of
>jonlowe at aol.com
>Sent: Thursday, August 24, 2006 12:21 PM
>To: nsrca-discussion at lists.nsrca.org
>Subject: Re: [NSRCA-discussion] DS 8411sa Servo Oscillation on Rudder
>
>Jim,
>This only manifests itself at neutral, and both cables are tight.
>Nothing is slipping, and I don't use ferrules.  In this particular
>case, I don't see how ackerman would be involved.
>
>Jon
>
>-----Original Message-----
>From: jivey61 at bellsouth.net
>To: nsrca-discussion at lists.nsrca.org
>Sent: Thu, 24 Aug 2006 7:21 AM
>Subject: Re: [NSRCA-discussion] DS 8411sa Servo Oscillation on Rudder
>
>Jon
>Read this about pull-pull.
>This will also happen if your cable ends slip. If you put the cable
>through the ferrule just one time it may be slipping. Bad geometry will
>cause this also.
> 
>Jim Ivey
> 
> 
> 
>http://members.cox.net/bdfelice/Ackerman/ackerman.htm
>----- Original Message -----
>From: JonLowe at aol.com
>To: nsrca-discussion at lists.nsrca.org
>Sent: Thursday, August 24, 2006 7:38 AM
>Subject: [NSRCA-discussion] DS 8411sa Servo Oscillation on Rudder
>
>
>I'm running a JR 8411sa on rudder on my Aggressor, pull-pull, using the
>setup that Troy Newman recommends (ss control line cable, NMP links at
>the servo end, and MK links at the rudder, etc.). For the first 75 or
>so flights, I had no issues.  Then, the servo started self oscillating
>around neutral, even with the engine not running, on the ground if the
>rudder stick was bumped.  The surface buzzes back and forth about 1/4",
>until damped out by grabbing the surface.  Thinking it was a servo pot
>going bad, I changed out the servo.  After two or three flights, same
>problem appeared.  Then thinking it must be a natural frequency issue
>in the linkage exciting the feedback loop in the servo, I tightened up
>on the pull-pull somewhat.  It wasn't loose before (these cables, as
>Troy says, don't stretch at all), but I increased tension somewhat. 
>That helped for about 3 flights, then the problem reappeared.  These
>servos are new 8411's, self converted to SA with a new plastic gear
>package.  I've gone thru the linkage completely, and find no evidence
>of anything amiss. I've changed nothing in the setup from the
>first flight. 
> 
>I believe I read somewhere in the past, about some 8411's doing this
>because the feedback loop in the servo was too tight, and could be
>corrected by sending them back to Horizon.  Can anyone shed some light
>on this?  I'm about to install an 8611 on rudder, but would like to
>track down this issue with the 8411s.
> 
>Thanks.
> 
>Jon Lowe
>
>
>
>--------
>
>
>_______________________________________________
>NSRCA-discussion mailing list
>NSRCA-discussion at lists.nsrca.org
>http://lists.nsrca.org/mailman/listinfo/nsrca-discussion
>_______________________________________________
>NSRCA-discussion mailing list
>NSRCA-discussion at lists.nsrca.org
>http://lists.nsrca.org/mailman/listinfo/nsrca-discussion
>
>________________________________________________________________________
>Check out AOL.com today. Breaking news, video search, pictures, email
>and IM. All on demand. Always Free.
>
>_______________________________________________
>NSRCA-discussion mailing list
>NSRCA-discussion at lists.nsrca.org
>http://lists.nsrca.org/mailman/listinfo/nsrca-discussion
>
>
>
>_______________________________________________
>NSRCA-discussion mailing list
>NSRCA-discussion at lists.nsrca.org
>http://lists.nsrca.org/mailman/listinfo/nsrca-discussion