X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from cdptpa-omtalb.mail.rr.com ([75.180.132.123] verified) by logan.com (CommuniGate Pro SMTP 5.3.9) with ESMTP id 4487572 for flyrotary@lancaironline.net; Thu, 30 Sep 2010 11:47:45 -0400 Received-SPF: pass receiver=logan.com; client-ip=75.180.132.123; envelope-from=eanderson@carolina.rr.com Return-Path: X-Authority-Analysis: v=1.1 cv=R3xZCyK5Rzzq4RgmEA8QIQ3hFZTdsD3z+kRPUs1QTwQ= c=1 sm=0 a=_BDd92krOsoA:10 a=rPkcCx1H5rrOSfN0dPC7kw==:17 a=arxwEM4EAAAA:8 a=r1ClD_H3AAAA:8 a=Ia-xEzejAAAA:8 a=ayC55rCoAAAA:8 a=1VPSJWL81OYIGZMbWewA:9 a=UE-S1vIcjrod4Dt5M20A:7 a=9IW_jao-uCIobMZqEJt-CKomCNwA:4 a=wPNLvfGTeEIA:10 a=EzXvWhQp4_cA:10 a=2U47UX1HuPtwZo4t:21 a=1i1L4a0Dj6sQqfPZ:21 a=pedpZTtsAAAA:8 a=E93lBu2AAAAA:8 a=LaPdxsmrjhDds9Z9GJ8A:9 a=k79YRv5vHy_O6w9GeNwA:7 a=Y2M3vYj97v6l_ZV_p6oDJk37kQMA:4 a=eJojReuL3h0A:10 a=hO30gm18fF0A:10 a=MpuOTR30KwMA:10 a=FOUTPhXFUAcA:10 a=zgjei8Deq7QA:10 a=NWVoK91CQyQA:10 a=7vYDwjJ7evkiVAuQ:21 a=BqypwEsi6Etq9Tf7:21 a=rPkcCx1H5rrOSfN0dPC7kw==:117 X-Cloudmark-Score: 0 X-Originating-IP: 174.110.167.5 Received: from [174.110.167.5] ([174.110.167.5:50455] helo=EdPC) by cdptpa-oedge01.mail.rr.com (envelope-from ) (ecelerity 2.2.3.46 r()) with ESMTP id 3A/A9-06710-7F0B4AC4; Thu, 30 Sep 2010 15:47:09 +0000 Message-ID: From: "Ed Anderson" To: "Rotary motors in aircraft" References: In-Reply-To: Subject: Re: [FlyRotary] Re: New SAG Theory Discussions of SAG Date: Thu, 30 Sep 2010 11:46:53 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0064_01CB6095.2D3B0F70" X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 14.0.8117.416 X-MimeOLE: Produced By Microsoft MimeOLE V14.0.8117.416 This is a multi-part message in MIME format. ------=_NextPart_000_0064_01CB6095.2D3B0F70 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable 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 deterioration with Mogas or 100LL - not certain why = it would be different between the two? IF not significantly different, = then that leaves the lead enhanced corrosion as the major culprit - at = least that is the way it appears 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 plugs - 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 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, You take good notes. Just a couple of clarifications: The decrease in the thermal = conductivity of the copper core may be the result of thermal cycling = causing development of porosity within the copper. This is independent = of the corrosion going 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 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 accelerated by the use of 100LL. The cure is still to install new spark plugs. =20 I have colder spark plugs from Racing Beat that are recommended for = prolonged use in high RPM high power applications. At best, the colder = plugs will merely delay the onset of SAG but won't prevent it from = happening eventually. It will be some time before the results of using = those plugs will be known. Steve Boese =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 = access to a scanning electron microscope or spectrum analyzer {:>)) and = analysis indicates a possible alternative reason for SAG other than = fouling.=20 It basically boils down to a theory of pre-ignition based on the = deteorating heat removal capacity of the plug. =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 parts of the plug becoming hot enough = to trigger 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 plug and one of the = overheated plug causing SAG. Preignition generally leads to detonation = which does not appear to be happening (at least no one 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 detonation = 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 colder 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.andersonee.com http://www.eicommander.com . 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 = someone go over the alternative theory with the ones of us that were not = in attendance? 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, both?? Bill B ------=_NextPart_000_0064_01CB6095.2D3B0F70 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Thanks for the clarification, Steve
 
However, that raises a new question.  = If the=20 porosity is even  a significant contributing factor=20 to thermal cycling, I would expect the same thermal cycling=20 deterioration with Mogas or 100LL - not certain why it would be = different=20 between the two?  IF not significantly different, then that leaves = the lead=20 enhanced corrosion as the major culprit - at least that is the way it = appears to=20 me.
 
Agree, regardless of cause - the answer is = replace the=20 plugs - however, if you discover the colder plugs last longer - then = that would=20 permit me to reduce my bushel basket storage of old spark plugs - = cleaning (even=20 if it were possible) does not appear to be a option any longer=20 {:>)
 
Ed
 
Edward L. Anderson
Anderson Electronic = Enterprises=20 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=20 SAG

Ed,
 
You take good notes.
 
Just a couple of clarifications:  = The=20 decrease in the thermal conductivity of the copper core may be the = result of=20 thermal cycling causing development of porosity within the = copper. =20 This is independent of the corrosion going on between the Mn alloy=20 electrode sheath and the insulator.  So there are two essentially=20 independent mechanisms contributing to the heat range change of the = spark plug=20 with age. 
 
The development of the porosity within = the copper=20 is not particularly affected by the type of fuel whereas the corrosion = between=20 the Mn alloy sheath and the insulator is accelerated by the use of=20 100LL.
 
The cure is still = to install new=20 spark plugs. 
 
I have colder = spark plugs from=20 Racing Beat that are recommended for prolonged use in high RPM high = power=20 applications.  At best, the colder plugs will merely delay the = onset of SAG=20 but won't prevent it from happening eventually.  It will be = some time=20 before the results of using those plugs will be = known.
 
Steve Boese
 
  
 
From: Rotary motors = in aircraft=20 [flyrotary@lancaironline.net] On Behalf Of Ed Anderson=20 [eanderson@carolina.rr.com]
Sent: Thursday, September 30, 2010 = 8:46=20 AM
To: Rotary motors in aircraft
Subject: = [FlyRotary] New=20 SAG Theory Discussions of SAG

In a nut shell, Steve's excellent data gathering = (how many=20 of use have access to a scanning electron microscope or spectrum = analyzer=20 {:>)) and analysis indicates a possible alternative reason for SAG = other than=20 fouling. 
 
 It basically boils down to a theory of = pre-ignition=20 based on the deteorating heat removal capacity of the plug.  =
 
There is a copper core (the photos showing the = two cores)=20 in the center of the ceramic cone which is responsible for conducting = 90% of the=20 heat away from the center electrode.  Based on Steve's' electron = microscope=20 viewing of two cores (one new and one having been used in a 100LL = environment),=20 it appears that the plug using leaded gasoline has corrosion occurring = on the=20 boundary between this copper core and the surrounding (hot) = elements.  This=20 layer of corrosion hinders heat removal from the plug leading to parts = of the=20 plug becoming hot enough to trigger pre-ignition.
 
This SAG tends to happened at high power = settings and=20 reducing power tends to make it go away (for a while).  Steve's = theory is=20 that the plug encounters max heat and temperature at high power settings = and=20 that reducing the power permits the plug to cool off enough for the = pre-ignition=20 to go away (for a while).
 
So we now have two theories - one is the fouled = plug and=20 one of the overheated plug causing SAG.  Preignition generally = leads to=20 detonation which does not appear to be happening (at least no one is = finding the=20 typical detonation damage to the rotary engine).  A possible reason = is the=20 quenching effect of the less than optimum shape of the rotary combustion = space=20 may tend to delay or prevent the onset of detonation damage that one = would=20 expect from continuous preignition caused by a too hot = plug.
 
I believe Steve intends to see if he can find = some colder=20 plugs (the ones that conduct heat better) and see if that extends the = time=20 between SAG.  Currently I find that roughly 25-30 hours is about = the max I=20 can get using 100LL before SAG sets in, whereas Tracy and others have = well over=20 150 hours using unleaded Mogas.  So if the colder plugs extend the = time=20 before SAG, I would say that pretty much would suggest Steve's theory is = correct=20 - if Not, then perhaps the fouled Plug theory still has merit or it = could be=20 some other phenomena happening.
 
Steve, my apologies if I did not present your = case as well=20 as you could
 
Ed
 
Edward L. Anderson
Anderson Electronic = Enterprises=20 LLC
305 Reefton Road
Weddington, NC 28104
http://www.andersonee.com
http://www.eicommander.com
 
.
 
 

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

I understand = that there=20 was a presentation on SAG at the meeting.  Can someone go over the=20 alternative theory with the ones of us that were not in = attendance?  It=20 looked like someone had a scanning electron microscope photo that they = were=20 showing!  Wow!  Are we getting sophisticated or what!!  = Was this=20 an explanation of the cause, or ideas for prevention, = both??

 

Bill=20 B

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