X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from mail-ey0-f180.google.com ([209.85.215.180] verified) by logan.com (CommuniGate Pro SMTP 5.3.10) with ESMTP id 4600019 for flyrotary@lancaironline.net; Thu, 02 Dec 2010 12:24:29 -0500 Received-SPF: pass receiver=logan.com; client-ip=209.85.215.180; envelope-from=msteitle@gmail.com Received: by eyf18 with SMTP id 18so5409356eyf.25 for ; Thu, 02 Dec 2010 09:23:53 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:received:in-reply-to :references:date:message-id:subject:from:to:content-type; bh=UItcjqadLMab1qr1KLeT3B0AhI96U4pqL/wj2ss18Eg=; b=sI1aIhphxePAiqzG/MPpsg2Ihr4MAqlYbhiPFXSCXSAJrrKh8SDjujJqgn7k2VoSky rvenFl4+DdCsvahtL8yNiXP22i7BGstLG5RI+GpJze7B0UDDo+Oz2WjC+ie7UQ1XpAND Rlr5pgnA3QUMzqbMi2gofAc1Kjp/iagkdYrAE= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; b=P9K3zIyizkO7d8PZWkNOjy/QusMlO93MP+EFVxlK61PZBBtSPUMv1uqUafDGAbELgo BI8hFsdb9sltfw6ZWJcKjiuXoX2oHQaCva8z2jihkRr+zD0vBl2MRcFx5BkwtA6H81Cd 21o7guhcZ5+7S4dlh2VlFb2hbVvxId/TBBtBc= MIME-Version: 1.0 Received: by 10.213.26.15 with SMTP id b15mr1285853ebc.13.1291310631004; Thu, 02 Dec 2010 09:23:51 -0800 (PST) Received: by 10.213.34.212 with HTTP; Thu, 2 Dec 2010 09:23:50 -0800 (PST) In-Reply-To: References: Date: Thu, 2 Dec 2010 11:23:50 -0600 Message-ID: Subject: Re: [FlyRotary] Re: Reactive Muffler Design for PP was [FlyRotary] Re: Modified header Calculations From: Mark Steitle To: Rotary motors in aircraft Content-Type: multipart/alternative; boundary=0015174a050a752f63049670af9f --0015174a050a752f63049670af9f Content-Type: text/plain; charset=ISO-8859-1 Ed, It sounds like it might work, but also appears to be very restrictive. Did you make any measurements regarding flow restriction? Maybe a larger diameter main body would alleviate the back pressure to an acceptable level, maybe not. I would want to run some tests first. What do you make of this site? http://en.wikibooks.org/wiki/Acoustics/Filter_Design_and_Implementation I think we can pretty much rule out "absorptive" type mufflers for our purposes. Wasn't Tracy's early muffler a "reactive" type (Hushpower)? As I recall it was heavy, but it worked very well. Mark On Thu, Dec 2, 2010 at 10:30 AM, Ed Anderson wrote: > I agree, Finn. It probably would not take much, but I just got to the > point I was tired of messing with it and put on the HushPower II. I always > felt I was just one more step away from making it successful - but did not > take it. Just too leery of learning to weld with only one good eye ball > left {:>) > > The 5/8" SS threaded shaft ran through the middle of the tube/discs with a > jam nut on each side of each disc. The shaft/rod was not anchored > otherwise. However, I did have a squished "Fishtail" end so that the last > disc could not back out of the tube. > > Ed > > *From:* Finn Lassen > *Sent:* Thursday, December 02, 2010 10:45 AM > *To:* Rotary motors in aircraft > *Subject:* [FlyRotary] Re: Reactive Muffler Design for PP was [FlyRotary] > Re: Modified header Calculations > > Hi Ed, > > Not that I'm going to jump on this right away, but it seems that it would > be relatively easy to rosette weld the tips of the discs. Drill 1/8" (or > slightly bigger) holes through the tube at the center of each disc tip. > > But, how did you secure the 5/8" shaft itself? > > Finn > > On 12/1/2010 5:45 PM, Ed Anderson wrote: > > Mark, > > Since you have not gotten to the muffler part of your design, here are some > thoughts (Yes, I did do 6 muffler experiments - don't ask me why) > > The one design that was "almost" totally successful in achieving my goals > is attached. Hard to make out the details, but enough to give you the > general ideal. > > My objective was trying to decided how to muffler the shock wave (which > creates most of the ear problems) but let the exhaust gas flow freely. My > conclusion was that reactive design muffler was the only acceptable choice > given our constraints. > > What I came up with was the idea of stuffing (I put five but I think three > would make a considerable difference) disc with outer parts cut into blades > and bent at a 45 deg angle into a tube. Looked a bit like an old farm > windmill. > > The idea behind this approach was if you looked head on at the fan-disc - > you see basically a solid metal front. That is what the shock wave would > see and most (a lot?) of the energy would be reflected back toward the > engine (actually to the next disc in the tube). The bent blades on the > other hand would permit exhaust gas to flow with minimum restriction. > > It really did deaden the sound where folks could stand by the wing tip with > no problem hearing someone else talk. I was thrilled. It also met my > minimum restriction as I could still get my 6000 rpm static. > > Ok, what went wrong - well, not being a welder I resorted to other methods > - which ultimately failed. > > Two things occurred - > > one if the disc broke loose of the small 5/8" thread SS shaft from the Jam > nuts on each side holding the disc, well, the disc could (and did) begin to > spin inside the tube like the turbine wheel of a jet engine. This > windmilling effect acted just like a windmilling prop on the exhaust gas and > definitely impeded gas flow. So can not permit the disc to spin (the tips > polished the inside of the tube where the spun) > > Second because I donot weld, I did not secure the tips of the blades of > the disc to the sides of the tube. Well the shock wave naturally causes > those blades to flex and eventually break off. > > The SS disc were 2" in diam 1/8 thick and fit really nice inside the 2 1/4" > tubes. I cut slots in the outer part of the SS disc and then used pliers to > bend the tabs to an approx 45 deg angle (see attached Jep). > > So none of this was difficult to fabricate (tedious perhaps but not > difficult). > > I gave up on it because without welding skills I could not figure out away > to secure the tips of the blades to the tube to give them better support. > Perhaps better than disc would have been cones but couldn't find any {:>). > > So since I couldn't see any way around my lack of welding (and too cheap to > hire someone), I went the hushpower II route. > > Just thought I would throw some fuel on your fire {:>) > > FWIW > > Ed > > > > --0015174a050a752f63049670af9f Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Ed,=A0

It sounds like it might work, but also appears to= be very restrictive. =A0Did you make any measurements regarding flow restr= iction? =A0Maybe a larger diameter main body would alleviate the back press= ure to an acceptable level, maybe not. =A0I would want to run some tests fi= rst.

I= think we can pretty much rule out "absorptive" type mufflers for= our purposes. =A0Wasn't Tracy's early muffler a "reactive&quo= t; type (Hushpower)? =A0As I recall it was heavy, but it worked very well.<= /div>

Mark


O= n Thu, Dec 2, 2010 at 10:30 AM, Ed Anderson <eanderson@carolina.rr.com> wrote:
I agree, Finn.=A0 It probably would=A0 not take= =20 much, but I just got to the point I was tired of messing with it and put on= the=20 HushPower II.=A0 I always felt I was just one more step away from making it= =20 successful - but did not take it.=A0 Just too leery of learning to weld wit= h=20 only one good eye ball left {:>)
=A0
The 5/8" SS threaded shaft ran through the m= iddle of the=20 tube/discs with a jam nut on each side of each disc.=A0 The shaft/rod was n= ot=20 anchored otherwise.=A0 However, I did have a squished "Fishtail" = end so that=20 the last disc could not back out of the tube.
=A0
Ed

Sent: Thursday, December 02, 2010 10:45 AM
Subject: [FlyRotary] Re: Reactive Muffler Design for PP w= as=20 [FlyRotary] Re: Modified header Calculations

Hi Ed,

Not that I'm going to jump on this right a= way, but=20 it seems that it would be relatively easy to rosette weld the tips of the d= iscs.=20 Drill 1/8" (or slightly bigger) holes through the tube at the center o= f each=20 disc tip.

But, how did you secure the 5/8" shaft=20 itself?

Finn

On 12/1/2010 5:45 PM, Ed Anderson wrote:=20
=20
Mark,
=A0
Since you have not gotten to the muffler part o= f your=20 design, here are some thoughts (Yes, I did do 6 muffler experiments - don= 't=20 ask me why)
=A0
The one design=A0that was "almost" to= tally successful=20 in achieving my goals is attached.=A0 Hard to make out the details, but= =20 enough to give you the general ideal.
=A0
My objective was trying to decided how to muffl= er the=20 shock wave (which creates most of the ear problems) but let the exhaust g= as=20 flow freely.=A0 My conclusion was that reactive design muffler was the on= ly=20 acceptable choice given our constraints.
=A0
What I came up with was the idea of stuffing (I= =A0=20 put five but I think three would make a considerable difference) disc wit= h=20 outer parts cut into blades and bent at a 45 deg angle into a tube.=A0=20 Looked a bit like an old farm windmill.
=A0
=A0 The idea behind this approach was if you lo= oked=20 head on at the fan-disc - you see basically a solid metal front.=A0 That = is=20 what the shock wave would see and most (a lot?) of the energy would be=20 reflected back toward the engine (actually to the next disc in the=20 tube).=A0 The bent blades on the other hand would permit exhaust gas to= =20 flow with minimum restriction.
=A0
It really did deaden the sound where folks coul= d stand=20 by the wing tip with no problem hearing someone else talk.=A0I was=20 thrilled.=A0 It also met=A0 my minimum restriction as I could still get= =20 my 6000 rpm static.
=A0
Ok, what went wrong - well, not being a welder = I=20 resorted to other methods - which ultimately failed.=A0
=A0
=A0Two things occurred -
=A0
one if the disc broke loose of the small 5/8&qu= ot; thread SS=20 shaft from the Jam nuts on each side holding the disc, well, the disc cou= ld=20 (and did) begin to spin inside the tube like the turbine wheel of a jet= =20 engine.=A0This windmilling effect acted just like a windmilling prop on t= he=20 exhaust gas and definitely impeded gas flow.=A0 So can not permit the dis= c=20 to spin (the tips polished the inside of the tube where the spun)<= /div>
=A0
=A0Second because I donot weld, I did not secur= e the=20 tips of the blades of the disc to the sides of the tube.=A0 Well the shoc= k=20 wave naturally causes those blades to flex and eventually break=20 off.
=A0
The SS disc were 2" in diam 1/8 thick=A0an= d fit=20 really nice inside the 2 1/4" tubes.=A0 I cut slots in the outer par= t of=20 the SS=A0disc and then used pliers to bend the tabs to an approx 45 deg= =20 angle (see attached Jep).
=A0
So none of this was difficult to fabricate (ted= ious=20 perhaps but not difficult).
=A0
I gave up on it because without welding skills = I could=20 not figure out away to secure the tips of the blades to the tube to give = them=20 better support.=A0 Perhaps better than disc would have been cones but=20 couldn't find any {:>).
=A0
So since I couldn't see any way around my l= ack of=20 welding (and too cheap to hire someone), I went=A0 the hushpower II=20 route.
=A0
Just thought I would throw some fuel on your fi= re=20 {:>)
=A0
FWIW
=A0
Ed




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