X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from poplet2.per.eftel.com ([203.24.100.45] verified) by logan.com (CommuniGate Pro SMTP 5.3.5) with ESMTP id 4219260 for flyrotary@lancaironline.net; Mon, 12 Apr 2010 20:33:08 -0400 Received-SPF: none receiver=logan.com; client-ip=203.24.100.45; envelope-from=lendich@aanet.com.au Received: from sv1-1.aanet.com.au (mail.aanet.com.au [203.24.100.34]) by poplet2.per.eftel.com (Postfix) with ESMTP id EB0B317381C for ; Tue, 13 Apr 2010 08:32:31 +0800 (WST) Received: from ownerf1fc517b8 (203.171.92.134.static.rev.aanet.com.au [203.171.92.134]) by sv1-1.aanet.com.au (Postfix) with SMTP id 5D125BEC053 for ; Tue, 13 Apr 2010 08:32:30 +0800 (WST) Message-ID: <1A1F4646C5E1448693FBA512815C6108@ownerf1fc517b8> From: "George Lendich" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Mistral Muffler Date: Tue, 13 Apr 2010 10:32:33 +1000 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0035_01CADAF4.A06ACE30" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.5843 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579 X-Antivirus: avast! (VPS 100412-2, 04/12/2010), Outbound message X-Antivirus-Status: Clean This is a multi-part message in MIME format. ------=_NextPart_000_0035_01CADAF4.A06ACE30 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Lynn, Very interesting, I hadn't seen this design before, I would consider it = simpler to manufacture than the first, therefore the latest before the = accident. I do like the design because of the simplicity - but there are = things I would change. Correct me if I'm wrong, but it appears that their mixing (cold air with = exhaust ) within the muffler. I could be wrong here as I can't see down = the cold air tube and there doesn't appear to be any/many air outlets = for cooling within the outer jacket. I would only cool using the outer = jacket. Secondly there is no tube from the inner exhaust housing feeding into = the main exhaust pipe. Of course there doesn't have to be, but to enable = maximum cooling air to evacuate (and mix with the exhaust within the = exhaust pipe), a low pressure area has to be created - it's what's = called exhaust augmentation in some designs, however in this design it's = probably more like cold air augmentation, whereas the exhaust is sucking = in the cold air. Thirdly the use of cones at the ends would help break up the sound = waves - however it introduces complexity and cost. Overall not a bad design at all, I wonder if the welds at the manifold = broke. In this design there is the opportunity to reinforce those joints = with some flanges. Easy enough to do and the work is hidden. I wish I'd seen this design before I did mine. there are a couple of = ideas I would consider using. George ( down under) Ernest,=20 =20 Copy you on that! What material type and thickness was the Mistral = muffler? Anyone know what their design was like? I know that something = fatigued and plugged the flow, but I never saw a drawing of their = muffler or had anyone explain how the failure actually occurred. It = could have been a baffle plate that was not well supported on all sides. = I don't see how that could happen to my muffler as the tube is welded = to both end plates and the exhaust gasses don't strike the tube directly = but swirl around it. Yes, a piece may fatigue over time and crack off, = but I can't imagine how it could plug up the exhaust path. But I guess = anything is possible if Murphy has his way. I'll keep a close eye on it = though. With a little finessing, I'm pretty sure I can get my little = inspection camera up the tailpipe. If that fails, I can remove one of = the O2 sensors and stick the camera through the hole for a peek inside. = =20 Mark =20 =20 Here is one version of the Mistral muffler. Said to be the failed = version. Well thought out. Superb exicution. Note that there appears to = be a slip join in the main body between the flanges. The whole muffler = is encased in a cooling sleeve with a big blast tube on one end and a = coaxial exhaust areounf the down pipe.=20 =20 My vote for the failure point is the flat disc closing the end of the = perf tube.=20 =20 Nothing flat survives the pounding. If its flat it dies. Round, = conical or spherical, yes. Flat no. =20 Lynn E. Hanover=20 -------------------------------------------------------------------------= ----- -- Homepage: http://www.flyrotary.com/ Archive and UnSub: = http://mail.lancaironline.net:81/lists/flyrotary/List.html ------=_NextPart_000_0035_01CADAF4.A06ACE30 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
 Lynn,
Very interesting, I hadn't seen this = design before,=20 I would consider it simpler to manufacture than the first, = therefore  the=20 latest before the accident. I do like the design because of the = simplicity - but=20 there are things I would change.
Correct me if I'm wrong, but it appears = that their=20 mixing (cold air with exhaust ) within the muffler. I could = be wrong=20 here as I can't see down the cold air tube and there doesn't appear to = be=20 any/many air outlets for cooling within the outer jacket. I would only = cool=20 using the outer jacket.
Secondly there is no tube from the inner exhaust housing feeding = into the=20 main exhaust pipe. Of course there doesn't have to be, but to enable = maximum=20 cooling air to evacuate (and mix with the exhaust within the exhaust = pipe), a=20 low pressure area has to be created  - = it's what's=20 called exhaust augmentation in some designs, however in this design it's = probably more like cold air augmentation, whereas the exhaust is sucking = in the=20 cold air.
Thirdly the use of cones  at the = ends=20 would  help break up the sound waves - however it introduces = complexity and=20 cost.
 
Overall not a bad design at all, I = wonder if the=20 welds at the manifold broke. In this design there is the opportunity to=20 reinforce those joints with some flanges. Easy enough to do and the work = is=20 hidden.
I wish I'd seen this design before I = did mine.=20 there are a couple of ideas I would consider using.
George ( down under)
Ernest,=20
 
Copy you on that!  What material type and thickness = was the=20 Mistral muffler?  Anyone know what their design was like?  I = know=20 that something fatigued and plugged the flow, but I never saw a = drawing of=20 their muffler or had anyone explain how the failure actually = occurred. =20 It could have been a baffle plate that was not well supported on all=20 sides.  I don't see how that could happen to my muffler as the = tube is=20 welded to both end plates and the exhaust gasses don't strike the tube = directly but swirl around it.  Yes, a piece may fatigue over time = and=20 crack off, but I can't imagine how it could plug up the exhaust = path. =20 But I guess anything is possible if Murphy has his way.  I'll = keep a=20 close eye on it though.  With a little finessing, I'm pretty sure = I can=20 get my little inspection camera up the tailpipe.  If that fails, = I can=20 remove one of the O2 sensors and stick the camera through the hole for = a peek=20 inside. 
 
Mark 
 
Here is one = version of=20 the Mistral muffler. Said to be the failed version. Well thought out. = Superb=20 exicution. Note that there appears to be a slip join in the main body = between=20 the flanges.  The whole muffler is encased in a cooling sleeve = with a big=20 blast tube on one end and a coaxial exhaust areounf the down pipe.=20
 
My vote for the failure point is the flat disc closing = the end=20 of the perf tube.
 
Nothing flat survives the pounding. If = its=20 flat it dies. Round, conical or spherical, yes. Flat = no.
 
Lynn E.=20 Hanover=20

--
Homepage:  http://www.flyrotary.com/
Archive and=20 UnSub:  =20 = http://mail.lancaironline.net:81/lists/flyrotary/List.html
------=_NextPart_000_0035_01CADAF4.A06ACE30--