X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Thu, 19 Jan 2012 09:01:32 -0500 Message-ID: X-Original-Return-Path: Received: from snt0-omc3-s47.snt0.hotmail.com ([65.54.51.84] verified) by logan.com (CommuniGate Pro SMTP 5.4.3) with ESMTP id 5355577 for lml@lancaironline.net; Wed, 18 Jan 2012 19:30:39 -0500 Received-SPF: pass receiver=logan.com; client-ip=65.54.51.84; envelope-from=gary21sn@hotmail.com Received: from SNT112-DS1 ([65.55.90.135]) by snt0-omc3-s47.snt0.hotmail.com with Microsoft SMTPSVC(6.0.3790.4675); Wed, 18 Jan 2012 16:30:03 -0800 X-Originating-IP: [24.216.249.79] X-Originating-Email: [gary21sn@hotmail.com] X-Original-Message-ID: X-Original-Return-Path: gary21sn@hotmail.com From: "Gary Edwards" X-Original-To: "Lancair Mailing List" References: Subject: Re: Ceramic exhaust coatings X-Original-Date: Wed, 18 Jan 2012 16:30:14 -0800 In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_04DE_01CCD5FE.76721820" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: MSN 9 Seal-Send-Time: Wed, 18 Jan 2012 16:30:14 -0800 X-MimeOLE: Produced By MSN MimeOLE V10.20.0091.1100 X-OriginalArrivalTime: 19 Jan 2012 00:30:03.0203 (UTC) FILETIME=[7C35F130:01CCD641] This is a multi-part message in MIME format. ------=_NextPart_000_04DE_01CCD5FE.76721820 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Fred, Fred, Fred, Your impatience with an ignorant person such as me is readily apparent. A few responses. ...You fail to understand the thermal problem.... I'm ignorant, but not that dumb. I understand the thermal difference. = My piston tops were also coated, but not because it makes me feel good. ...The ceramic coating inside the exhaust pipe reduces the heat flow to = the metal a bit, but only a small bit. The metal still gets hot, but = its temperature is lowered slightly. Even slight lowering of = temperature helps a little bit, so it is up to you to decide if it is = worth the cost and effort. If it feels good, then do it.... So you do concur that it is of some benefit. That is what my original = post was all about. Whew! I have it in the pipes, but not because it = makes me feel good, because it works. ...Don't disparage things that feel good. That is why we fly, build = nice airplanes, and enjoy sex. Don't knock it... Where in my post did I disparage flying, building airplanes, and = especially sex? ...Come on, Gary, to you seriously consider a motor cycle spending most = of its life at low power settings to be comparable to an aircraft engine = running 50F lean of peak at 65% power? If you want to make it a good = comparison, open the throttle on your motor cycle, accelerate up to = about 90% of top speed, back off the throttle to hold this speed, and = then continue for 1000 hours. After that I would like a report... Re-read my post Fred. No where did say I was comparing a motorcycle to = the aircraft. It was a "side note" about the benefit of the exterior = chrome for that application. Please, your response was uncalled for. Not being an intellectual, as you are perceived to be from here, I base = my actions on what I see has or has not worked in the real world. = Non-stainless steel exhaust pipes are commonly utilized in experimental = aircraft, and based on successful flying years, may be a viable option = to consider. Thank you for the detailed analysis of metal content in = the latter portion of your post, although it really wasn't necessary, as = it is way beyond my interest level of the original subject at hand. This is my last post on the subject. If you feel compelled to get the = last word in, my flame suit, well, better yet, my ceramic coating is on. = Gary =20 =20 =20 ----- Original Message -----=20 From: Frederick Moreno=20 To: lml@lancaironline.net=20 Sent: Wednesday, January 18, 2012 7:34 AM Subject: [LML] Fw: Re: Ceramic exhaust coatings Gary wrote:=20 "So, all those racers out there (motorcycles, quads, drag cars, = sand rails, drag boats, snowmobiles, etc.) with heat coatings on top of = their pistons are only using it to "feel good"?" No.=20 You fail to understand the thermal problem. Ceramic coating = piston tops and cylinder head cavities has been shown to gain 1-2% more = horsepower at full power. I had my pistons and cylinder heads coated = for this reason, and because it made me feel good. =20 But it works on pistons because the thermal event lasts through = the power stroke only, about 180 degrees of rotation, or about 12-15 = milliseconds. The peak heating only occurs for about half of this when = the pressures and temperatures are highest. This is when most of the = power is made, and avoiding a bit of heat loss for a few milliseconds is = worthwhile. =20 Here is the difference between pistons and exhaust pipes. In = case of the piston, the thermal "wave" from the transient heating only = penetrates a few mils into the ceramic coating during the event. Then = the gas temperature falls dramatically, falls some more during the = exhaust stroke, and then there is a blast of cold air and evaporating = avgas taken in and compressed. The top few mills of ceramic coating are = cooled, a reduced amount of heat reaches the piston or head metal, and = the cycle continues.=20 Contrast this very rapid transient piston heating and cooling = with the exhaust pipe. Blast of hot gas, then slowing of the hot gas, = then some oscillations of hot gas back and forth in the pipe, and then = another blast of hot gas. A thermocouple buried in this rapidly = changing flow can not respond fast enough to report instantaneously, and = displays an "average" temperature which we interpret as the EGT. So = does the inside of the exhaust pipe.=20 With no cooling event occurring, the thermal coating inside the = pipe soaks up energy, temperature rises and stays high, and the = interface between ceramic and metal gets hot. Then the metal gets hot = and it stays hot. Everything gets red hot. This is not aluminum piston = country.=20 The ceramic coating inside the exhaust pipe reduces the heat = flow to the metal a bit, but only a small bit. The metal still gets = hot, but its temperature is lowered slightly. Even slight lowering of = temperature helps a little bit, so it is up to you to decide if it is = worth the cost and effort. If it feels good, then do it. =20 Don't disparage things that feel good. That is why we fly, = build nice airplanes, and enjoy sex. Don't knock it.=20 Gary also wrote: "On a side note, I know it sure keeps my chrome = motorcycle pipes from turning brown or blue. Oh, and they have not = shown symptoms of failure after years of use. Read below." Come on, Gary, to you seriously consider a motor cycle spending = most of its life at low power settings to be comparable to an aircraft = engine running 50F lean of peak at 65% power? If you want to make it a = good comparison, open the throttle on your motor cycle, accelerate up to = about 90% of top speed, back off the throttle to hold this speed, and = then continue for 1000 hours. After that I would like a report on your = chrome exhaust pipes. Then we have something to compare and discuss = objectively because only then will the operating conditions and duration = be approximately the same. ...Don't do it. It will droop off due to gravity having = absolutely no creep strength, and will drop in a heap in a few hours. = And it will rust to dust in a few cycles.... ...Mild steel has no capability in this operating regime. Gary wrote further: "Why is it then that there are hundreds, no = thousands, of experimentals out there (several at this airport) with = steel [my emphasis added] exhaust systems that have been flying for = years, decades, with no problems or symptoms that you describe?" I am sorry if the context of my comment in italics above evaded = you. The question I was responding to was about using mild steel for = aircraft exhaust pipes. Pursuant to earlier emails discussing I noted = that even stainless steel had low creep strength at the higher = temperatures of interest. Mild steel has virtually no creep resistance = or oxidation resistance at the same temperatures. Build mild steel = headers for your airplane and when they get hot, they will get soft, = creep, and deform. I will leave it to you to look up the creep strength = and oxidation rates of mild steel in the temperature range of interest = for this discussion, namely 1200-1500F.=20 As to your comment about experimental (aircraft ) operating for = years with no problems, let me again clarify since it appears my earlier = text was unclear in conveying its message. I was referring to mild = steel (considered to be 1020, 1030, etc. ) while aircraft exhaust pipes = are all made with a steel alloy normally referred to as STAINLESS = steel, usually 321 stainless, an austenitic alloy with a mix of = properties making it attractive for exhaust pipes on airplanes. Unlike = mild steel which is almost entirely iron (Fe) with a bit of carbon and = low quantities of other alloying agents, 321 stainless steel has the = following alloying agents:=20 Fe, <0.08% C, 17-19% Cr, 9-12% Ni, <2% Mn, <1% Si, 0.3-0.7% Ti, = <0.045% P, <0.03% S Translation: lots of nickel and chromium and = important additions of titanium. What this means is summarized as = follows:=20 "Grades 321 and 347 are the basic austenitic 18/8 steel (Grade = 304) stabilised by Titanium (321) or Niobium (347) additions. These = grades are used because they are not sensitive to intergranular = corrosion after heating within the carbide precipitation range of = 425-850=B0C. Grade 321 is the grade of choice for applications in the = temperature range of up to about 900=B0C, combining high strength, = resistance to scaling and phase stability with resistance to subsequent = aqueous corrosion." See = http://www.azom.com/article.aspx?ArticleID=3D967 for more insights.=20 Mild steel it ain't.=20 I hope this helps your understanding.=20 Fred Moreno =20 =20 =20 ------=_NextPart_000_04DE_01CCD5FE.76721820 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Fred, Fred, Fred,
 
Your impatience with an ignorant person such as me is readily=20 apparent.
 
A few responses.
 
...You fail to understand the thermal problem....
 
I'm ignorant, but not that dumb.  I understand the = thermal=20 difference.  My piston tops were also coated, but not because it = makes me=20 feel good.
 
 
...The ceramic coating inside the exhaust pipe reduces the heat = flow to=20 the metal a bit, but only a small bit.  The metal still gets hot, = but its=20 temperature is lowered slightly.  Even slight lowering of = temperature=20 helps a little bit, so it is up to you to decide if it is worth the cost = and=20 effort.  If it feels good, then do it....
 
So you do concur that it is of some benefit.  That is what my = original=20 post was all about.  Whew!  I have it in the pipes, but = not=20 because it makes me feel good, because it works.
 
 
...Don't  disparage things that feel good.  That = is why=20 we fly, build nice airplanes, and enjoy sex.  Don't knock = it...
 
Where in my post did I disparage flying, building = airplanes,=20 and especially sex?
 
 
...Come on, Gary, to you seriously consider a motor cycle=20 spending most of its life at low power settings to be comparable to = an=20 aircraft engine running 50F lean of peak at 65% power?  If you want = to make=20 it a good comparison, open the throttle on your motor cycle, accelerate = up to=20 about 90% of top speed, back off the throttle to hold this speed, and = then=20 continue for 1000  hours.  After that I would like a=20 report...
 
Re-read my post Fred.  No where did say I was comparing a = motorcycle=20 to the aircraft.  It was a "side note" about the benefit of the = exterior=20 chrome for that application.  Please, your response was = uncalled=20 for.
 
 
Not being an intellectual, as you are perceived to be from = here,=20 I base my actions on what I see has or has not worked in the real=20 world.  Non-stainless steel exhaust pipes are commonly = utilized in=20 experimental aircraft, and based on successful flying years, may be a = viable=20 option to consider.  Thank you for the detailed analysis = of metal=20 content in the latter portion of your post, although it really wasn't = necessary,=20 as it is way beyond my interest level of the original subject at = hand.
 
This is my last post on the subject.  If you feel compelled to = get the=20 last word in, my flame suit, well, better yet, my ceramic coating is=20 on. 
 
Gary     
 
  
 
 
 
 
 
 
----- Original Message -----
From: Frederick Moreno =
Sent: Wednesday, January 18, = 2012 7:34=20 AM
Subject: [LML] Fw: Re: Ceramic = exhaust=20 coatings

Gary wrote:
 
"So, all those racers out there (motorcycles, quads, drag = cars,=20 sand rails, drag boats, snowmobiles, etc.) with heat = coatings on=20 top of their pistons are only using it to "feel = good"?"
 
No.
 
You fail to understand the thermal problem.  Ceramic = coating=20 piston tops and cylinder head cavities has been shown to gain = 1-2% more=20 horsepower at full power.   I  had = my pistons and=20 cylinder heads coated for this reason, and because it made me = feel=20 good. 
 
But it works on pistons because the thermal event lasts = through the=20 power stroke only, about 180 degrees of rotation, or about 12-15 = milliseconds.  The peak heating only occurs for=20 about half of this when the pressures and temperatures are=20 highest.  This is when most of the power is made, and = avoiding=20 a bit of heat loss for a few milliseconds is worthwhile.  =
 
Here is the difference between pistons and exhaust = pipes.  In=20 case of the piston, the thermal "wave" from the transient  = heating=20 only penetrates a few mils into the ceramic coating during the=20 event.  Then the gas temperature falls dramatically, falls = some=20 more during the exhaust stroke, and then there is a blast of = cold air=20 and evaporating avgas taken in and compressed.  The top few = mills=20 of ceramic coating are cooled, a reduced amount = of heat=20 reaches the piston or head metal, and the cycle continues. =
 
Contrast this very rapid transient piston heating and = cooling with=20 the exhaust pipe.  Blast of hot gas, then slowing of the = hot gas,=20 then some oscillations of hot gas back and forth in the pipe, = and then=20 another blast of hot gas.  A thermocouple buried in this = rapidly=20 changing flow can not respond fast enough to report = instantaneously, and=20 displays an "average" temperature which we interpret as the = EGT. =20 So does the inside of the exhaust pipe.
 
With no cooling event occurring, the thermal coating inside = the=20 pipe soaks up energy, temperature rises and stays high, and the=20 interface between ceramic and metal gets hot.  Then the = metal gets=20 hot and it stays hot.  Everything gets red hot. This is not = aluminum piston country.
 
The ceramic coating inside the exhaust pipe reduces the = heat flow=20 to the metal a bit, but only a small bit.  The metal still = gets=20 hot, but its temperature is lowered slightly.  Even = slight=20 lowering of temperature helps a little bit, so it is up to you = to decide=20 if it is worth the cost and effort.  If it feels good, then = do=20 it. 
 
Don't  disparage things that feel good.  = That is why=20 we fly, build nice airplanes, and enjoy sex.  Don't knock = it.=20
 
Gary also wrote: "On a side note, I know it sure keeps my = chrome=20 motorcycle pipes from turning brown or blue.  Oh, and they = have not=20 shown symptoms of failure after years of use.  Read = below."
 
Come on, Gary, to you seriously consider a motor cycle=20 spending most of its life at low power settings to be = comparable to=20 an aircraft engine running 50F lean of peak at 65% power?  = If you=20 want to make it a good comparison, open the throttle on your = motor=20 cycle, accelerate up to about 90% of top speed, back off the = throttle to=20 hold this speed, and then continue for 1000  hours.  = After=20 that I would like a report on your chrome exhaust = pipes.  =20 Then we have something to compare and discuss objectively = because only=20 then will the operating conditions and duration be approximately = the=20 same.
 
...Don't do it.  It will droop off due to=20 gravity having absolutely no creep strength, and will drop = in a=20 heap in a few hours.  And it will rust to dust in a few=20 cycles....
...Mild steel has no capability in this operating=20 regime.
 
Gary wrote further: "Why is it then that there are = hundreds, no=20 thousands, of experimentals out there (several at this airport) = with=20 steel [my emphasis added] exhaust systems that = have=20 been flying for years, decades, with no problems or = symptoms that=20 you describe?"
 
I am sorry if the context of my comment in italics above = evaded=20 you.  The question I was responding to was about using = mild=20 steel for aircraft exhaust pipes.  Pursuant to = earlier=20 emails discussing I noted that even stainless = steel had=20 low creep strength at the higher temperatures of interest.  = Mild steel has virtually no creep resistance or = oxidation resistance at the same temperatures.  Build = mild=20 steel headers for your airplane and when they get hot, = they=20 will get soft, creep, and deform.  I will leave it to you = to look=20 up the creep strength and oxidation rates of mild steel in the=20 temperature range of interest for this discussion, namely = 1200-1500F.=20
 
As  to your comment about experimental (aircraft ) = operating=20 for years with no problems, let me again clarify since it = appears=20 my earlier text was unclear in conveying its message.  I = was=20 referring to mild steel (considered to be 1020, = 1030,=20 etc. ) while aircraft exhaust pipes are all made with a = steel alloy=20 normally referred to as  STAINLESS steel, = usually=20 321 stainless, an austenitic alloy with a mix of properties = making=20 it attractive for exhaust pipes on airplanes.  Unlike = mild=20 steel which is almost entirely iron (Fe) with a = bit of=20 carbon and low quantities of other alloying agents,=20 321 stainless steel has the following = alloying=20 agents:

Fe, <0.08% C, 17-19% Cr, 9-12% Ni, <2% Mn, <1% Si, = 0.3-0.7%=20 Ti, <0.045% P, <0.03% S   Translation: lots of = nickel=20 and chromium and important additions of titanium.   = What this=20 means is summarized as follows:

"Grades 321 and 347 are the basic austenitic 18/8 steel = (Grade 304)=20 stabilised by Titanium (321) or Niobium (347) additions. These = grades=20 are used because they are not sensitive to=20 intergranular corrosion after heating within the carbide = precipitation range of 425-850=B0C. Grade 321 is the = grade of=20 choice for applications in the temperature range of up to about = 900=B0C,=20 combining high strength, resistance to scaling and phase = stability with resistance to subsequent aqueous=20 corrosion."  See  http://www.azom= .com/article.aspx?ArticleID=3D967 for=20 more insights.

Mild steel it ain't.

I hope this helps your understanding.

Fred Moreno

 
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