X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from m12.lax.untd.com ([64.136.30.75] verified) by logan.com (CommuniGate Pro SMTP 5.0.8) with SMTP id 999868 for flyrotary@lancaironline.net; Mon, 27 Feb 2006 11:28:11 -0500 Received-SPF: pass receiver=logan.com; client-ip=64.136.30.75; envelope-from=alwick@juno.com Received: from m12.lax.untd.com (localhost [127.0.0.1]) by m12.lax.untd.com with SMTP id AABCAGLB4ALB6AU2 for (sender ); Mon, 27 Feb 2006 08:26:34 -0800 (PST) Received: (from alwick@juno.com) by m12.lax.untd.com (jqueuemail) id LH8UC3P5; Mon, 27 Feb 2006 08:26:15 PST To: flyrotary@lancaironline.net Date: Mon, 27 Feb 2006 08:23:39 -0800 Subject: Re: [FlyRotary] Exhaust Blowout Message-ID: <20060227.082608.3968.2.alwick@juno.com> X-Mailer: Juno 5.0.33 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary=--__JNP_000_15e1.6baf.5ee5 X-Juno-Line-Breaks: 8-6,10-12,17-18,22-31,33,37-38,45-46,48-62,63-32767 From: al p wick X-ContentStamp: 20:10:101566732 X-MAIL-INFO:296a5f8b6a1eea6b1ec727c76e9ecffa634aae8aeb6e9aca1a7ac373b35bdedb1bcaea9393bf02ee8f8f4bbf43a73e1fe39b4b3b9b836b7b0a479bd7a3276ebfd7470ad707d7022f2a1bfe8f7f4b6f4b67bf2b83deba2b3e43372ae7ce4e5a33ba876e9fef07ef5e072a1abb77139e7edf1a X-UNTD-OriginStamp: L941HVjjYzDhN3itp//mkDGnGSARpCqIz0zJiw1KdmBI1IiL7IMVQw== X-UNTD-Peer-Info: 127.0.0.1|localhost|m12.lax.untd.com|alwick@juno.com This message is in MIME format. Since your mail reader does not understand this format, some or all of this message may not be legible. ----__JNP_000_15e1.6baf.5ee5 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit I'd be real quick to duplicate someone's successful exhaust design. Keeps the risk items to minimum. This failure could have easily occurred in first flight. PRETEND IT DID. You would have no prop remaining. Weld tab on your tail pipe, safety wire to aircraft. Control the failure modes. I'd give strong consideration to eliminating the figure 8 welds at muffler. I would have tail pipe be a slip fit at that point. So your tail pipe floats. That would require safety wire and clamp on tail pipe to prevent it from departing plane, but would eliminate mechanical moment on those welds. I'm not all that familiar with rotary characteristics. Puzzled why tail pipe is such large diameter (2 pipes seam welded together). I would think that exhaust pulse at any one moment is no greater than a single tube diameter. Maybe someone can explain to me. -al wick Artificial intelligence in cockpit, Cozy IV powered by stock Subaru 2.5 N9032U 200+ hours on engine/airframe from Portland, Oregon Prop construct, Subaru install, Risk assessment, Glass panel design info: http://www.maddyhome.com/canardpages/pages/alwick/index.html On Sun, 26 Feb 2006 23:09:32 -0800 "Joe Hull" writes: I’m still struggling with tuning my rotary/microtech. I spent an hour or so running it yesterday and ended up a little closer on the tuning front but also ended up with a blown out exhaust/muffler. It’s come apart at a bunch of places – not the welds but the Inconel itself next to the welds. The exhaust pipe coming out of the “tangential tube” is/was in the profile of an “8” without the connection in the center. An engineer friend of mine who looked it over said it makes sense - after the fact - that the exhaust pulses were causing the tube to flex at the center joint. It appears to have started at the outboard end and went all the way to the center tube and then, perhaps from vibration, cracked out the pipes except for about ˝” from the center connection. The main manifold – runners and the tangential tube – are all sound with no signs of stress. So, be careful out there! Pics attached. Thanx, Joe Hull Cozy Mk-IV #991 (Done Building! In Phase1 Flight Test - 0 hrs flown) Redmond (Seattle), Washington -al wick Artificial intelligence in cockpit, Cozy IV powered by stock Subaru 2.5 N9032U 200+ hours on engine/airframe from Portland, Oregon Prop construct, Subaru install, Risk assessment, Glass panel design info: http://www.maddyhome.com/canardpages/pages/alwick/index.html ----__JNP_000_15e1.6baf.5ee5 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable
I'd be real quick to duplicate someone's successful exhaust = design.=20 Keeps the risk items to minimum. This failure could have easily occurred in= =20 first flight. PRETEND IT DID. You would have no prop remaining. Weld tab on= your=20 tail pipe, safety wire to aircraft. Control the failure modes.
 
 
I'd give strong consideration to eliminating the figure 8 welds at = muffler.=20 I would have tail pipe be a slip fit at that point. So your tail pipe = floats.=20 That would require safety wire and clamp on tail pipe to prevent it from=20 departing plane, but would eliminate mechanical moment on those welds.
 
I'm not all that familiar with rotary characteristics. Puzzled why = tail=20 pipe is such large diameter (2 pipes seam welded together). I would think = that=20 exhaust pulse at any one moment is no greater than a single tube diameter. = Maybe=20 someone can explain to me.
 

-al wick
Artificial intelligence in cockpit, Cozy IV powered by= =20 stock Subaru 2.5
N9032U 200+ hours on engine/airframe from Portland,=20 Oregon
Prop construct, Subaru install, Risk assessment, Glass panel = design=20 info:
http:= //www.maddyhome.com/canardpages/pages/alwick/index.html
 
On Sun, 26 Feb 2006 23:09:32 -0800 "Joe Hull" <joeh@pilgrimtech.com> writes:

I=92m still struggling with= tuning=20 my rotary/microtech. I spent an hour or so running it yesterday and ended= up a=20 little closer on the tuning front but also ended up with a blown out=20 exhaust/muffler. It=92s come apart at a bunch of places =96 not the welds= but the=20 Inconel itself next to the welds.

 

The exhaust pipe coming out= of the=20 =93tangential tube=94 is/was in the profile of an =938=94 without the = connection in=20 the center. An engineer friend of mine who looked it over said it makes = sense=20 - after the fact - that the exhaust pulses were causing the tube to flex = at=20 the center joint.  It appears to have started at the outboard end = and=20 went all the way to the center tube and then, perhaps from vibration, = cracked=20 out the pipes except for about =BD=94 from the center=20 connection.

 

The main manifold =96 = runners and=20 the tangential tube =96 are all sound with no signs of=20 stress.

So, be careful out=20 there!

 

Pics=20 attached.

 

Thanx,

Joe=20 Hull

Cozy Mk-IV #991 (Done = Building! In=20 Phase1 Flight Test - 0 hrs flown)

Redmond (Seattle), Washington

 

-al wick
Artificial intelligence in= =20 cockpit, Cozy IV powered by stock Subaru 2.5
N9032U 200+ hours on=20 engine/airframe from Portland, Oregon
Prop construct, Subaru install, = Risk=20 assessment, Glass panel design=20 info:
http://www.maddyhome.com/canardpages/pages/alwick/index.html
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