X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from imr-ma05.mx.aol.com ([64.12.100.31] verified) by logan.com (CommuniGate Pro SMTP 5.3.9) with ESMTP id 4487627 for flyrotary@lancaironline.net; Thu, 30 Sep 2010 12:16:00 -0400 Received-SPF: pass receiver=logan.com; client-ip=64.12.100.31; envelope-from=Bktrub@aol.com Received: from imo-ma02.mx.aol.com (imo-ma02.mx.aol.com [64.12.78.137]) by imr-ma05.mx.aol.com (8.14.1/8.14.1) with ESMTP id o8UGFFdY021489 for ; Thu, 30 Sep 2010 12:15:15 -0400 Received: from Bktrub@aol.com by imo-ma02.mx.aol.com (mail_out_v42.9.) id q.f01.9b26f55 (37144) for ; Thu, 30 Sep 2010 12:15:11 -0400 (EDT) Received: from smtprly-dd01.mx.aol.com (smtprly-dd01.mx.aol.com [205.188.84.129]) by cia-ma03.mx.aol.com (v129.4) with ESMTP id MAILCIAMA036-d3e64ca4b787200; Thu, 30 Sep 2010 12:15:11 -0400 Received: from Webmail-m106 (webmail-m106.sim.aol.com [64.12.224.160]) by smtprly-dd01.mx.aol.com (v129.4) with ESMTP id MAILSMTPRLYDD012-d3e64ca4b787200; Thu, 30 Sep 2010 12:15:03 -0400 References: To: flyrotary@lancaironline.net Subject: Re: [FlyRotary] Re: New SAG Theory Discussions of SAG Date: Thu, 30 Sep 2010 12:15:03 -0400 X-AOL-IP: 208.46.237.130 In-Reply-To: X-MB-Message-Source: WebUI MIME-Version: 1.0 From: bktrub@aol.com X-MB-Message-Type: User Content-Type: multipart/alternative; boundary="--------MB_8CD2ED1C613CC5E_17B8_26B7_Webmail-m106.sysops.aol.com" X-Mailer: AOL Webmail 32679-STANDARD Received: from 208.46.237.130 by Webmail-m106.sysops.aol.com (64.12.224.160) with HTTP (WebMailUI); Thu, 30 Sep 2010 12:15:03 -0400 Message-Id: <8CD2ED1C47337A4-17B8-13FF@Webmail-m106.sysops.aol.com> X-Spam-Flag:NO X-AOL-SENDER: Bktrub@aol.com ----------MB_8CD2ED1C613CC5E_17B8_26B7_Webmail-m106.sysops.aol.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="us-ascii" Ok , since I am incapable of public embarassment, what is SAG other than what= I see in the mirror? Brian =20 -----Original Message----- From: Ed Anderson To: Rotary motors in aircraft Sent: Thu, Sep 30, 2010 8:46 am Subject: [FlyRotary] Re: New SAG Theory Discussions of SAG Thanks for the clarification, Steve =20 However, that raises a new question. If the porosity is even a significa= nt contributing factor to thermal cycling, I would expect the same thermal= cycling deterioration with Mogas or 100LL - not certain why it would be= different between the two? IF not significantly different, then that lea= ves the lead enhanced corrosion as the major culprit - at least that is th= e way it appears to me. =20 Agree, regardless of cause - the answer is replace the plugs - however, if= you discover the colder plugs last longer - then that would permit me to= reduce my bushel basket storage of old spark plugs - cleaning (even if it= were possible) does not appear to be a option any longer {:>) =20 Ed =20 Edward L. Anderson Anderson Electronic Enterprises LLC 305 Reefton Road Weddington, NC 28104 http://www.andersonee.com http://www.eicommander.com =20 =20 From: Steven W. Boese=20 Sent: Thursday, September 30, 2010 11:14 AM To: Rotary motors in aircraft=20 Subject: [FlyRotary] Re: New SAG Theory Discussions of SAG Ed, =20 You take good notes. =20 Just a couple of clarifications: The decrease in the thermal conductivity= of the copper core may be the result of thermal cycling causing developme= nt of porosity within the copper. This is independent of the corrosion go= ing on between the Mn alloy electrode sheath and the insulator. So there= are two essentially independent mechanisms contributing to the heat range= change of the spark plug with age. =20 =20 The development of the porosity within the copper is not particularly affe= cted by the type of fuel whereas the corrosion between the Mn alloy sheath= and the insulator is accelerated by the use of 100LL. =20 The cure is still to install new spark plugs. =20 =20 I have colder spark plugs from Racing Beat that are recommended for prolon= ged use in high RPM high power applications. At best, the colder plugs wi= ll merely delay the onset of SAG but won't prevent it from happening event= ually. It will be some time before the results of using those plugs will= be known. =20 Steve Boese =20 =20 =20 From: Rotary motors in aircraft [flyrotary@lancaironline.net] On Behalf Of= Ed Anderson [eanderson@carolina.rr.com] Sent: Thursday, September 30, 2010 8:46 AM To: Rotary motors in aircraft Subject: [FlyRotary] New SAG Theory Discussions of SAG In a nut shell, Steve's excellent data gathering (how many of use have acc= ess to a scanning electron microscope or spectrum analyzer {:>)) and analy= sis indicates a possible alternative reason for SAG other than fouling.=20 =20 It basically boils down to a theory of pre-ignition based on the deteorat= ing heat removal capacity of the plug. =20 =20 There is a copper core (the photos showing the two cores) in the center of= the ceramic cone which is responsible for conducting 90% of the heat away= from the center electrode. Based on Steve's' electron microscope viewing= of two cores (one new and one having been used in a 100LL environment),= it appears that the plug using leaded gasoline has corrosion occurring on= the boundary between this copper core and the surrounding (hot) elements.= This layer of corrosion hinders heat removal from the plug leading to pa= rts of the plug becoming hot enough to trigger pre-ignition. =20 This SAG tends to happened at high power settings and reducing power tends= to make it go away (for a while). Steve's theory is that the plug encoun= ters max heat and temperature at high power settings and that reducing the= power permits the plug to cool off enough for the pre-ignition to go away= (for a while). =20 So we now have two theories - one is the fouled plug and one of the overhe= ated plug causing SAG. Preignition generally leads to detonation which do= es not appear to be happening (at least no one is finding the typical deto= nation damage to the rotary engine). A possible reason is the quenching= effect of the less than optimum shape of the rotary combustion space may= tend to delay or prevent the onset of detonation damage that one would ex= pect from continuous preignition caused by a too hot plug. =20 I believe Steve intends to see if he can find some colder plugs (the ones= that conduct heat better) and see if that extends the time between SAG.= Currently I find that roughly 25-30 hours is about the max I can get usi= ng 100LL before SAG sets in, whereas Tracy and others have well over 150= hours using unleaded Mogas. So if the colder plugs extend the time befor= e SAG, I would say that pretty much would suggest Steve's theory is correc= t - if Not, then perhaps the fouled Plug theory still has merit or it coul= d be some other phenomena happening. =20 Steve, my apologies if I did not present your case as well as you could =20 Ed =20 Edward L. Anderson Anderson Electronic Enterprises LLC 305 Reefton Road Weddington, NC 28104 http://www.andersonee.com http://www.eicommander.com =20 . =20 =20 From: Bill Bradburry=20 Sent: Thursday, September 30, 2010 9:59 AM To: Rotary motors in aircraft=20 Subject: [FlyRotary] Discussions of SAG I understand that there was a presentation on SAG at the meeting. Can som= eone go over the alternative theory with the ones of us that were not in= attendance? It looked like someone had a scanning electron microscope ph= oto that they were showing! Wow! Are we getting sophisticated or what!!= Was this an explanation of the cause, or ideas for prevention, both?? =20 Bill B ----------MB_8CD2ED1C613CC5E_17B8_26B7_Webmail-m106.sysops.aol.com Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset="us-ascii"
Ok ,
since I am incapable of public embarassment, what is SAG other than= what I see in the mirror?
 
Brian 



-----Original Message-----
From: Ed Anderson <eanderson@carolina.rr.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Thu, Sep 30, 2010 8:46 am
Subject: [FlyRotary] Re: New SAG Theory Discussions of SAG

Thanks for the clarification, Steve
 
However, that raises a new question.  If = ;the porosity is even  a significant contributing factor to=  thermal cycling, I would expect the same thermal cycling deteriorati= on with Mogas or 100LL - not certain why it would be different betwee= n the two?  IF not significantly different, then that leaves the lead= enhanced corrosion as the major culprit - at least that is the way it app= ears to me.
 
Agree, regardless of cause - the answer is replace= the plugs - however, if you discover the colder plugs last longer - then= that would permit me to reduce my bushel basket storage of old spark plug= s - cleaning (even if it were possible) does not appear to be a option any= longer {:>)
 
Ed
 
Edward L. Anderson
Anderson Electronic Enterprises LLC
305 Reefton Road
Weddington, NC 28104
http://www.andersonee.com=
http://www.eicommander.= com
 
 

Sent: Thursday, September 30, 2010 11:14 AM
Subject: [FlyRotary] Re: New SAG Theory Discussions of SAG

Ed,
 
You take good notes.
 
Just a couple of clarifications: = The decrease in the thermal conductivity of the copper core may be the re= sult of thermal cycling causing development of porosity within the co= pper.  This is independent of the corrosion going on between the= Mn alloy electrode sheath and the insulator.  So there are two essen= tially independent mechanisms contributing to the heat range change of the= spark plug with age. 
 
The development of the porosity within= the copper is not particularly affected by the type of fuel whereas the= corrosion between the Mn alloy sheath and the insulator is accelerat= ed by the use of 100LL.
 
The cure is still to= install new spark plugs. 
 =
I have colder spark= plugs from Racing Beat that are recommended for prolonged use in hig= h RPM high power applications.  At best, the colder plugs will merely= delay the onset of SAG but won't prevent it from happening eventuall= y.  It will be some time before the results of using those plugs will= be known.
 
Steve Boese
 
  
 <= /div>
From: Rotary motors in= aircraft [flyrotary@lancai= ronline.net] On Behalf Of Ed Anderson [eanderson@carolina.rr.com]
Sent: Thursday, September 30, 2010 8:46 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] New SAG Theory Discussions of SAG

In a nut shell, Steve's excellent data gathering= (how many of use have access to a scanning electron microscope or spectru= m analyzer {:>)) and analysis indicates a possible alternative reason= for SAG other than fouling. 
 
 It basically boils down to a theory of pre-i= gnition based on the deteorating heat removal capacity of the plug. =
 
There is a copper core (the photos showing the two= cores) in the center of the ceramic cone which is responsible for conduct= ing 90% of the heat away from the center electrode.  Based on Steve's= ' electron microscope viewing of two cores (one new and one having been us= ed in a 100LL environment), it appears that the plug using leaded gasoline= has corrosion occurring on the boundary between this copper core and the= surrounding (hot) elements.  This layer of corrosion hinders heat re= moval from the plug leading to parts of the plug becoming hot enough to tr= igger pre-ignition.
 
This SAG tends to happened at high power settings= and reducing power tends to make it go away (for a while).  Steve's= theory is that the plug encounters max heat and temperature at high power= settings and that reducing the power permits the plug to cool off enough= for the pre-ignition to go away (for a while).
 
So we now have two theories - one is the fouled pl= ug and one of the overheated plug causing SAG.  Preignition generally= leads to detonation which does not appear to be happening (at least no on= e is finding the typical detonation damage to the rotary engine).  A= possible reason is the quenching effect of the less than optimum shape of= the rotary combustion space may tend to delay or prevent the onset of det= onation damage that one would expect from continuous preignition caused by= a too hot plug.
 
I believe Steve intends to see if he can find some= colder plugs (the ones that conduct heat better) and see if that extends= the time between SAG.  Currently I find that roughly 25-30 hours is= about the max I can get using 100LL before SAG sets in, whereas Tracy and= others have well over 150 hours using unleaded Mogas.  So if the col= der plugs extend the time before SAG, I would say that pretty much would= suggest Steve's theory is correct - if Not, then perhaps the fouled Plug= theory still has merit or it could be some other phenomena happening.
 
Steve, my apologies if I did not present your case= as well as you could
 
Ed
 
Edward L. Anderson
Anderson Electronic Enterprises LLC
305 Reefton Road
Weddington, NC 28104
http://www.anderson= ee.com
http://www.eicomma= nder.com
 
.
 
 

Sent: Thursday, September 30, 2010 9:59 AM
Subject: [FlyRotary] Discussions of SAG

I understand that= there was a presentation on SAG at the meeting.  Can someone go over= the alternative theory with the ones of us that were not in attendance?&n= bsp; It looked like someone had a scanning electron microscope photo that= they were showing!  Wow!  Are we getting sophisticated or what!= !  Was this an explanation of the cause, or ideas for prevention, bot= h??
 = ;
Bill B
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