X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from mail-pz0-f181.google.com ([209.85.222.181] verified) by logan.com (CommuniGate Pro SMTP 5.2.16) with ESMTP id 3839113 for flyrotary@lancaironline.net; Sun, 06 Sep 2009 14:47:28 -0400 Received-SPF: pass receiver=logan.com; client-ip=209.85.222.181; envelope-from=wdleonard@gmail.com Received: by pzk11 with SMTP id 11so607056pzk.3 for ; Sun, 06 Sep 2009 11:46:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:date:message-id:subject :from:to:content-type; bh=F1S2+Q1Op+8NhnR5gc+9UQZ4o0m+KgjkCFJRPb/uHbo=; b=esckXhKF0QtFXQOYMndcKnhF0dPXQC6dVQ2yg4m8NYoz+OzKui4Qraoyc87h0DTM2m NJr8RiIVZbY8PH8Qvyv7J1fVnQjSP2MZSbsQTDyCEK+AcYKhfL59O8BVCxYxlLM+4ZMy I1PIV+iTsT4Ugo5cYbbMYIqWJcrY9m2KqI8+g= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:date:message-id:subject:from:to:content-type; b=T5XY280K0I+9XwuRb6bL00Nwk9ySGf00tVaLripxqou7imh65xi/Xll2csWaYlPKkN 8aeJM/QSaUvAFmYIpulC5FPew8DJcpTompcuE/0/NnhlNPETdYFX1GAjETaeJMu4wJPg LqV9Bbn0jS3dQYsjZ1imTHpz0eNaRoWbvt4+I= MIME-Version: 1.0 Received: by 10.140.131.2 with SMTP id e2mr3230866rvd.98.1252262813264; Sun, 06 Sep 2009 11:46:53 -0700 (PDT) Date: Sun, 6 Sep 2009 11:46:53 -0700 Message-ID: <1c23473f0909061146meb1334ei4c4d3dcea4fc8e25@mail.gmail.com> Subject: Re: [FlyRotary] Muffling/ Morroso update From: David Leonard To: Rotary motors in aircraft Content-Type: multipart/alternative; boundary=000e0cd29510266b580472ed28e8 --000e0cd29510266b580472ed28e8 Content-Type: text/plain; charset=ISO-8859-1 I have been running the Morroso for the last 20 hours or so. Not sure it is the muffler, but I have noticed a definate decrease in power. Too bad because it did a nice job on the sound and only weighed 3 lbs. I think next I will empty out the flowmaster shell and reinstall it - then live with the noise. Maybe put in some lava rocks if I get tired of the noise again. Maybe try a fishmouth. -- David Leonard Turbo Rotary RV-6 N4VY http://N4VY.RotaryRoster.net http://RotaryRoster.net On Sun, Sep 6, 2009 at 10:19 AM, Lynn Hanover wrote: > Mark/Ed/Bill, > > I was thinking along the same lines as Bill - that the DNA is more > restrictive resulting in richer mixtures at equivalent MAP. My home made > muffler was a copy of the Moroso spiral flow mufflers, but with a larger > center tube. With my home made muffler I can look all the way through it so > the DNA is clearly more restrictive. Which is why I'm surprised it didnt > work better. > > The DNA sure looks better than my home made muffler. Weld quality is great. > Time will tell how it holds up. The home made muffler was Inconel so I > expect it would be more durable in the long run. > > The point of something else in the airflow path limiting HP is a good > point. One of things I've noticed is that I reach max power long before I > reach max throttle. Since I'm making enough power for good performance I > wasnt too worried about this, but I am curious. Once I reach about 3/4 > throttle I'm maxed out - the last 1/4 doesnt do anything. > > Mike Wills > RV-4 N144MW > > The first problem to overcome when muffling a rotary, is the supersonic > shock wave leaving the engine. If you can see through the muffler from end > to end, it is probable that some part of that shock wave will exit the > muffler. In order to slow the shock wave to subsonic it is required that the > muffler provide some pressure in front of, Or, to impinge on the moving wave > to slow it down. > > The Mazda racing muffler has an empty room at the front that allows the > shock wave to expand and drop to subsonic before muffling begins. You can > see through the Mazda muffler, but they address the supersonic problem early > in the process. They used to use lava rocks for the media, This stuff would > be turned to dust and expelled during the year, and need to be replaced. > > The center tube was perfed as was the front bulkhead. So pressure from the > front chamber could see the center tube cross section > and the perfed bulkhead area. So in that regard the muffler was ineffective > if the front chaomber failed to drop the shock wave to subsonic. However it > did, and could hold the strongest Rotary to 105 dB at 50 feet. (Full > throttle at best power RPM) Probably well above 9,000 RPM. > > So to muffle you drop the velocity, using volume changes. By cooling the > flow, by impinging on the flow with gasses collected in the front of the > muffler and reintroduced near the end of the muffler, by using the flow to > impinge on itself with splitters or divided flow tricks and reflectors. By > absorbing the highest pressure peaks in some form of replaceable media. By > absorbing the most offensive frequencies in tuned cavities. > > Once the supersonic problem is delt with, conventional car mufflers are > effective. > > My first muffler attempt started with the center tube being from a house > jack strut. About 1/8 wall probably 1010 steel. Large diameter holes in the > first 5 inches to help replicate the Mazda cavity muffler. Then a bulkhead > with 1/4" holes. Then a space of about 4" with no holes. Then thousands (it > seemed like) of 1/8" holes in the rest of the tube length. I worked pretty > well and then melted the center tube near the front. There was no media > involved. About 30" overall. > > The rotary is slightly more tolorant of back pressure than is suspected, > and this may be used to impinge > on fuffling flow. At the exhause flange, there is a negative pressure well > below ambient. A leak here draws cold air into the system and unburned fuel > ignites with a popping sound, like a 2 cycle scooter off the power. > > Perf tube mufflers take off the peaks and then impinge on the flow. So they > may affect tuning every where, and then change as the media melts into > little balls or is hammered to dust and leaves the muffler. > > It seemed to me that the Spintech was close to the best for this > application, and would like to have seen that run to destruction. > > Just my opinion, I could be completly wrong. > > Lynn E. Hanover > --000e0cd29510266b580472ed28e8 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
I have been running the Morroso for the last 20 hours or so.=A0 Not su= re it is the muffler, but I have noticed a definate decrease in power.=A0 T= oo bad because it did a nice job on the sound and only weighed 3 lbs.=A0
=A0
I think next I will empty out the flowmaster shell and reinstall it - = then live with the noise.=A0 Maybe put in some lava rocks if I get tired of= the noise again.=A0 Maybe try a fishmouth.
=A0
--
David Leonard

Turbo Rotary RV-6 N4VY
http://N4VY.RotaryRoster.net
http://RotaryRoster.net


On Sun, Sep 6, 2009 at 10:19 AM, Lynn Hanover <lehanover@gmail.= com> wrote:
Mark/Ed/Bill,
=A0
I was thinking along the same lines as= Bill - that the DNA is more restrictive resulting in richer mixtures at eq= uivalent MAP. My home made muffler was a copy of the Moroso spiral flow muf= flers, but with a larger center tube. With my home made muffler I can look = all the way through it so the DNA is clearly more restrictive. Which is why= I'm surprised it didnt work better.
=A0
The DNA sure looks better than my home= made muffler. Weld quality is great. Time will tell how it holds up. The h= ome made muffler was Inconel so I expect it would be more durable in the lo= ng run.
=A0
The point of something else in the air= flow path limiting HP is a good point. One of things I've noticed is th= at I reach max power long before I reach max throttle. Since I'm making= enough power for good performance I wasnt too worried about this, but I am= curious. Once I reach about 3/4 throttle I'm maxed out - the last 1/4 = doesnt do anything.
=A0
Mike Wills
RV-4 N144MW
=A0
The first problem to overcome when muffling a rotary, is the supersoni= c shock wave leaving the engine. If you can see through the muffler from en= d to end, it is probable that some part of that shock wave will exit the mu= ffler. In order to slow the shock wave to subsonic it is required that the = muffler provide some pressure in front of, Or, to impinge on the moving wav= e to slow it down.
=A0
The Mazda racing muffler has an empty room at the front that allows th= e shock wave to expand and drop to subsonic before muffling begins. You can= see through the Mazda muffler, but they address the supersonic problem ear= ly in the process. They used to use lava rocks for the media, This stuff wo= uld be turned to dust and expelled during the year, and need to be replaced= .
=A0
The center tube was perfed as was the front bulkhead. So pressure from= the front chamber could see the center tube cross section
and the perfed bulkhead area. So in that regard the muffler was ineffe= ctive if the front chaomber failed to drop the shock wave to subsonic. Howe= ver it did, and could hold the strongest Rotary to 105 dB at 50 feet. (Full= throttle at best power RPM) Probably well above 9,000 RPM.
=A0
So to muffle you drop the velocity, using volume changes. By cooling t= he flow, by impinging on the flow with gasses collected in the front of the= muffler and reintroduced near the end of the muffler, by using the flow to= impinge on itself with splitters or divided flow tricks and reflectors. By= absorbing the highest pressure peaks in some form of replaceable media. By= absorbing the most offensive frequencies in tuned cavities.
=A0
Once the supersonic problem is delt with, conventional car mufflers ar= e effective.
=A0
My first muffler attempt started with the center tube being from a hou= se jack strut. About 1/8 wall probably 1010 steel. Large diameter holes in = the first 5 inches to help replicate the Mazda cavity muffler. Then a bulkh= ead with 1/4" holes. Then a space of about 4" with no holes. Then= thousands (it seemed like) of 1/8" holes in the rest of the tube leng= th. I worked pretty well and then melted the center tube near the front. Th= ere was no media involved.=A0=A0About 30" overall.
=A0
The rotary is slightly more tolorant of back pressure than is suspecte= d, and this may be used to impinge
on fuffling flow. At the exhause flange, there is a negative pressure = well below ambient. A leak here draws cold air into the system and unburned= fuel ignites with a popping sound, like a 2 cycle scooter off the power.
=A0
Perf tube mufflers take off the peaks and then impinge on the flow. So= they may affect tuning every where, and then change as the media melts int= o little balls or is hammered to dust and leaves the muffler.
=A0
It seemed to me that the Spintech was close to the best for this appli= cation, and would like to have seen that run to destruction.
=A0
Just my opinion, I could be completly wrong.
=A0
Lynn E. Hanover



--000e0cd29510266b580472ed28e8--