X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from web1114.biz.mail.sk1.yahoo.com ([74.6.114.46] verified) by logan.com (CommuniGate Pro SMTP 5.3c3) with SMTP id 4015990 for flyrotary@lancaironline.net; Fri, 11 Dec 2009 16:48:44 -0500 Received-SPF: none receiver=logan.com; client-ip=74.6.114.46; envelope-from=admin@haaspowerair.com Received: (qmail 93228 invoked by uid 60001); 11 Dec 2009 21:48:08 -0000 Message-ID: <926304.92048.qm@web1114.biz.mail.sk1.yahoo.com> X-YMail-OSG: GvW8FFEVM1lUv1y_6wY3mlEmS86TES0IGZlosuTxaOxo_Pc78BUkTTzxqorHhil2oTzV6IguJGKju64c7WuI1qGfC47NzzsJoqCsLH12Jg.63QTUo5p5MUqy34HhXJKdaw3FKDmqNVjKOGjCga31w64YvZp4zd4Ck3k9bxF2kZbEggRI3RQcA_85Q9Orc5K2XWlncDbBqsoUaMUkIk_bCNhuC5t_d6wVNhCC2tYBfha6qxAGVCHH8Ofo8pYVSDk6rkVs_EjyuBtwyIb6YHSOs3Nj4TxZZTl2zj0fpkJSSAcQFtu.E_1F_UGHPzVFaTPF3oP8XPYBpWaP9EASrjFWjtrk0ozDigcc25U1gRDClHFsX5crW5e8pzukzI1pjdvLErU7Zm_gRPSiurvN58wD6s0c2U4zq1pL7YgAfueloORzGAscuEkcFB3Bw9mpUxppYHOMT12sbMETk0Ul_wBq3ctEQG1.rO6OZoQtf6Mz4TieNmcywccsiojHK6BhiO0bNyp8Jhk7myizgnuFLd7sl4r4pn0XBCvaKZA.rxvIXMA- Received: from [75.174.166.58] by web1114.biz.mail.sk1.yahoo.com via HTTP; Fri, 11 Dec 2009 13:48:07 PST X-Mailer: YahooMailClassic/9.0.19 YahooMailWebService/0.7.361.4 Date: Fri, 11 Dec 2009 13:48:07 -0800 (PST) From: stephen haas Subject: Re: [FlyRotary] Re: FW: [FlyRotary] Exhaust and Muffler designs. To: Rotary motors in aircraft In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="0-1767993856-1260568087=:92048" --0-1767993856-1260568087=:92048 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable The pic you posted clearly shows the prop extension. I originally saw the f= lange and imagined that the prop was alot closer then your actual applicati= on. I do=C2=A0love the canard and I am very close to ordering one for my ne= xt build..Not only are they fast they look KOOL !!!!!!!=C2=A0 Thanks again = for the answer to my question. =C2=A0 Tailwinds. --- On Fri, 12/11/09, Al Gietzen wrote: From: Al Gietzen Subject: [FlyRotary] Re: FW: [FlyRotary] Exhaust and Muffler designs. To: "Rotary motors in aircraft" Date: Friday, December 11, 2009, 8:27 AM Stephan; =C2=A0 Thanks. Yes, it heats the prop, but not enough to be deleterious.=C2=A0 I w= as concerned because my Catto prop has fiberglass wraps over wood.=C2=A0 Ea= rly in the testing I put thermal sensing tape on the prop blades. =C2=A0The= highest temp reached was about 130-135F, which I=E2=80=99m sure occurred d= uring full power climb. Cruise temps would be lower.=C2=A0 Catto=E2=80=99s = opinion was that it was nothing to be concerned about =E2=80=93 the strengt= h of the blade in the root area is all about the wood core. =C2=A0 The exhaust does of course deposit some stain on the prop.=C2=A0 It wipes o= ff relatively easily with Goof-Off (or similar).=C2=A0 Detergents take it o= ff, but it takes more scrubbing. =C2=A0The prop is painted with 2-stage acr= ylic, and after 170 hours there is no permanent discoloration of the clear = coat on the surface, so that tells me everything is fine.=C2=A0 There is no= w some minor discoloration of the cowl port at the exhaust exit. =C2=A0 I have a 6=E2=80=9D prop extension, so the distance from the exhaust pipe t= o the prop is about 8=E2=80=9D.=C2=A0 I chose this approach in the interest= of minimum drag. (Photo) =C2=A0 Al =C2=A0 Subject: [FlyRotary] Re: FW: [FlyRotary] Exhaust and Muffler designs. =C2=A0 Hi Al.... Very nice installation...=20 =C2=A0 One question. =C2=A0 Does the discharge of the exhaust that close to the prop transfer any heat = to it. I know the duration of the blade passing across the exhaust stream i= s very short and there is alot of air funneling around the cowl and dilutin= g the heat but.... Do you see any sign of heat ? Doe it leave=C2=A0an exhaust stain on the blade/ =C2=A0 Thanks in advance, --- On Wed, 12/9/09, Al Gietzen wrote: From: Al Gietzen Subject: [FlyRotary] FW: [FlyRotary] Exhaust and Muffler designs. To: "Rotary motors in aircraft" Date: Wednesday, December 9, 2009, 10:52 PM Phil; Here is a posting; with attachments, that I sent to the list about 6 months= ago. The inconel is .045 or .050=E2=80=9D; I=E2=80=99m not certain which.=C2=A0 = The fabricator (Mark Sadickas (sp?); referred by Dave Atkins) had the mater= ial.=C2=A0 Materials and labor came to $1950. =C2=A0 The secondary muffler is .032=E2=80=9D 321SS outside, with through-pipe and= ends of .049=E2=80=9D.=C2=A0 The outside of the secondary stays relatively= cool =E2=80=93 I learned that the O2 sensor would not get hot enough there= to give good readings, suggesting maybe about 900F. Al =C2=A0 -----Original Message----- From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Beh= alf Of Al Gietzen Sent: Sunday, June 08, 2008 12:15 PM To: Rotary motors in aircraft Subject: [FlyRotary] Exhaust and Muffler designs. =C2=A0 Exhaust and muffler design in the rotary installation is one of the more co= mplex of all the installation issues. There are, and have been so many vari= ations among the various installations that there is little statistical pro= of of anything. =C2=A0I=E2=80=99ll add a few comments and opinions that may= be relevant, and describe what I did. It may trigger some ideas for you to= think about. My system on the 20B is now approaching 100 hours =E2=80=93 n= ot a long term proof =E2=80=93 but it is still solid.=20 =C2=A0 The exhaust temps out of the port are very high, typically in the neighborh= ood of 1600F, and sometimes maybe 1700F.=C2=A0 Couple this with pressure pu= lses and vibrational loads, and corrosive environment, and you have a very = demanding situation. =C2=A0When you look at material properties to handle t= his, things narrow down pretty rapidly, particularly if you also want light= weight as we do in aviation.=C2=A0 Stainless steels, like 321, can handle = the temps and be a workable exhaust =E2=80=93 but, design for low stress le= vels then becomes a must, because SS are subject to =E2=80=98stress corrosi= on=E2=80=99 at these temps.=C2=A0 Combine the high temperatures and vibrati= onal stress and you get inter-granular corrosion which weakens the material= and it eventually falls apart. =C2=A0 On way to alleviate that is to use inconel.=C2=A0 It gives you higher tempe= rature capability and corrosion resistance.=C2=A0 And it gives you higher c= ost.=C2=A0 But is it worth it to reduce your risk a forced landing in an un= friendly place?=C2=A0 Compared to the total cost of your airplane it=E2=80= =99s a small amount.=C2=A0 Maybe cut cost somewhere where it is less critic= al to safety.=20 =C2=A0 Another thing to consider is that the more quickly you can expand the exhau= st gas, the more quickly you can deal with lower temperatures.=C2=A0 Charle= s Law =E2=80=93 temp (degree K) goes down in direct proportion to increased= volume.=C2=A0 This becomes more complex in an exhaust system because of ot= her factors, but it still works in your favor. =C2=A0The gas will expand do= wn a constant diameter pipe, but expanding into a BIG pipe can make a signi= ficant drop. =C2=A0 =C2=A0 That can be one of the advantages of the tangential muffler/manifold, or th= e design that Neil presented. =C2=A0The amount of the temp drop of course d= epends on the pressure in that bigger can. These designs have their own pos= sible failure modes associated with welded joints and thermal stresses, but= at least there is nothing there that is going to plug up the flow downstre= am.=C2=A0 The skill of the welder and the post-weld heat treatment are impo= rtant factors. =C2=A0 These units are generally bolted directly to the engine via the short heade= r pipes, so vibration loads are a factor. Ideally you=E2=80=99d like to hav= e stress (and thermal expansion) de-coupling between the engine and the muf= fler/manifold, but since the engine can move relative to it=E2=80=99s mount= you either have to accommodate significant movement, or support it to the = engine by some other means then the header pipes. =C2=A0 And then there is the matter of the exit pipe(s) and secondary mufflers. Th= ose have to be supported as well =E2=80=93 an unsupported length of pipe ex= tending from the muffler is an ideal candidate for some vibrational resonan= ce which will fail the system somewhere. And the further away from the engi= ne centerline, the greater the loads.=20 =C2=A0 My exhaust system is shown in the first attached photo. This is in a pusher= configuration. =C2=A0It is an inconel tangential manifold/muffler supporte= d to the engine by short inconel header pipes which are welded to a heavy R= B steel flange. It has a convex =E2=80=98head=E2=80=99 at the front, and a = conical outlet to the exit pipe.=C2=A0 It has internal vanes welded at an a= ngle on the inside surface opposite the exit from the headers (you can see = the welds on the outside) to help break up the pulses and direct the exhaus= t toward the exit. They also prevent possible =E2=80=9Cswirl-flow choking= =E2=80=9D which could increase back pressure.=C2=A0 There are =E2=80=98stra= ightening=E2=80=99 vanes in the conical exit section. =C2=A0 The exit pipe is clamped (custom heavy SS clamp) to the inlet pipe of the s= econdary muffler (I=E2=80=99ll call it a resonator). =C2=A0The resonator is= also of my design and is made of 321 SS.=C2=A0 It is basically a straight = through 2 =C2=BE=E2=80=9D pipe that is drilled full of =C2=BC=E2=80=9D hole= s (about 100), contained within outer 5=E2=80=9D dia. pipe. =C2=A0The inner= pipe has an orifice plate at the center which has a 1 5/8=E2=80=9D opening= .=C2=A0 This orifice produces some restriction to the flow through the reso= nator to force some of it outward through the holes, and back through the h= oles to exit. =C2=A0The purpose of the resonator is to knock down the press= ure peaks a bit more. =C2=A0Measurements on the dyno showed that resonator = knocked another 8 db off the sound level and had no noticeable effect on th= e HP. =C2=A0 The plug in the resonator closes a port originally intended for the O2 sens= or. But it didn=E2=80=99t work well in that location because the temperatur= e was too low (interesting, huh). I had to move it to the inlet pipe. =C2=A0 Last but not least, there is a SS support at the end which clamps solidly t= o the redrive. The clamp is designed to be rigid laterally, but to also be = an effective heat choke.=C2=A0 This supports the resonator, and reduces the= likelihood of any resonance vibration in the system. =C2=A0 I originally thought that the resonator internals may not last more than 50= hours, but at 95 hours they are still solid. Which brings up another point= .=C2=A0 It is easily inspected. I can see those internals from the exit end= , and I can stick a screwdriver or ratchet handle or whatever; in there and= bang around to be sure things are sound. =C2=A0I inspect all the welds in = the exhaust system every time I remove the cowl, or at least every 10 hours= or so.=C2=A0 Make your system inspectable, and keep an eye on it. =C2=A0 I wouldn=E2=80=99t call it =E2=80=9Cquiet=E2=80=9D, but I=E2=80=99ve had pe= ople say they like the way it sounds. Time will tell its reliability. =C2=A0 Best, =C2=A0 Al Gietzen =C2=A0 =C2=A0 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 If you g= o through the archives, you'll find lots of examples of failed muffler designs.=C2=A0 Many by your's truly.=C2=A0 I think I've trie= d every concoction known to man and the Swiss.=C2=A0 They all worked...=C2=A0 for a= while.=C2=A0=20 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 My best = overall design (see attached) is a 2" tube, full of holes inside a 5" tube.=C2=A0 All made of 16ga SS, all welded together.=C2=A0 Nee= dless to say, the flange is more like 3/16" - 1/4" SS.=C2=A0 The inside end of the 2= " tube is welded to the end cap of the 5" tube.=C2=A0 That blocks off the one end = of the 2" tube and secures it from movement.=C2=A0 The exhaust end of the 2" tube = is welded through a 2" hole in the other 5" end cap.=C2=A0 Rather than drillin= g the 2" tube full of round holes, we cut slots with a saw.=C2=A0 Then take a big= flat blade screwdriver, stick it in the slot and bend it over.=C2=A0 This create= s an oblong hole.=C2=A0 (Much easier than drilling into SS.=C2=A0 This is what w= ill go on the Volmer. =C2=A0 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 The soun= d is quite acceptable, it fits inside the cowl and Jim M.'s version lasted the life of the aircraft... 600+ hours. =C2=A0 Neil =C2=A0 PS: Are you considering Rough River? =C2=A0 =C2=A0 =C2=A0 -----Original Message----- From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Al Wick Sent: Saturday, June 07, 2008 4:57 PM To: Rotary motors in aircraft Subject: [FlyRotary] Re: Mistral Crash Analysis =C2=A0 C'mon guys. You do this every time there's a crash. Instantly go into=20 rationalization mode. It's unhealthy. Greatly increases risk builders won't= =20 take action. Increases risk you won't research it thoroughly. =C2=A0 A healthy response would be:" Here's another example of how our engines=20 produce unusually destructive exhaust temperature and pulses. We have a ric= h =C2=A0 history of broken exhaust components. We need to be very thorough when=20 designing and building exhaust." =C2=A0 I designed my own muffler. It had two inlets, two outlets. So if (when) my= =20 muffler failed, it could never block both pipes. I also put loose safety=20 wire around my pipes, because on a pusher loosing pipe wipes out prop. So= =20 basically, I assume stuff will=C2=A0 fail, then design it to control the wa= y it=20 fails. I've heard of rotary guys doing same type of thing. This is a good= =20 time to share those key items. =C2=A0 On your car, they deliberately design products to fail a certain way. They= =20 will make a component weak, so it fails first. They do that with wheels and= =20 hubs. So when the muffler fails, little pieces come apart, not big sections= ? =C2=A0 You guys do a great job of sharing successes, design and construction=20 details. This is another opportunity. =C2=A0 -al wick =C2=A0 =C2=A0 =C2=A0 =C2=A0 ).=C2=A0 Bu= t, I=20 serious doubt it will effect many who have researched the rotary and come t= o =C2=A0 understand its benefits - as for the rest, who cares {:>) > =C2=A0 =C2=A0 I'm certain it was a relief to Mistral that the culprit was not one = of=20 their engine components. =C2=A0 =C2=A0 =C2=A0 =C2=A0 Whew! a close one for sure. =C2=A0 =C2=A0 =C2=A0 =C2=A0 Hi Ed, =C2=A0 =C2=A0 =C2=A0 =C2=A0 Unfortunately, I bet the majority of people will only hear "Mistral= =20 rotary", "lost power", and "crash"=C2=A0 :-( =C2=A0 =C2=A0 =C2=A0 =C2=A0 Rusty (RV-3 taking forever.) =C2=A0 ____________________________________________________________ Orlando Vacations - Click Here! http://thirdpartyoffers.juno.com/TGL2141/fc/Ioyw6i3nK7u59LkagfZ5IcEgGqYcvPR= C wA85GgQITbFK9vE7wPGKFP/ =C2=A0 -- Homepage:=C2=A0 http://www.flyrotary.com/ Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html -----Inline Attachment Follows----- -- Homepage:=C2=A0 http://www.flyrotary.com/ Archive and UnSub:=C2=A0=C2=A0=C2=A0http://mail.lancaironline.net:81/lists/= flyrotary/List.html =C2=A0 -----Inline Attachment Follows----- -- Homepage:=C2=A0 http://www.flyrotary.com/ Archive and UnSub:=C2=A0=C2=A0=C2=A0http://mail.lancaironline.net:81/lists/= flyrotary/List.html --0-1767993856-1260568087=:92048 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: quoted-printable
The pic you posted clearly shows the pro= p extension. I originally saw the flange and imagined that the prop was alo= t closer then your actual application. I do love the canard and I am v= ery close to ordering one for my next build..Not only are they fast they lo= ok KOOL !!!!!!!  Thanks again for the answer to my question.
 
Tailwinds.

--- On Fri, 12/11/09, Al Gietzen <ALVenture= s@cox.net> wrote:

From: Al Gietzen <ALVentures@cox.net>
Su= bject: [FlyRotary] Re: FW: [FlyRotary] Exhaust and Muffler designs.
To: = "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Date: Fr= iday, December 11, 2009, 8:27 AM

Stephan;

 

Thanks. Yes, it hea= ts the prop, but not enough to be deleterious.  I was concerned becaus= e my Catto prop has fiberglass wraps over wood.  Early in the testing = I put thermal sensing tape on the prop blades.  The highest temp reach= ed was about 130-135F, which I=E2=80=99m sure occurred during full power cl= imb. Cruise temps would be lower.  Catto=E2=80=99s opinion was that it= was nothing to be concerned about =E2=80=93 the strength of the blade in t= he root area is all about the wood core.

 

The exhaust does of= course deposit some stain on the prop.  It wipes off relatively easil= y with Goof-Off (or similar).  Detergents take it off, but it takes mo= re scrubbing.  The prop is painted with 2-stage acrylic, and after 170= hours there is no permanent discoloration of the clear coat on the surface= , so that tells me everything is fine.  There is now some minor discol= oration of the cowl port at the exhaust exit.

 

I have a 6=E2=80=9D= prop extension, so the distance from the exhaust pipe to the prop is about= 8=E2=80=9D.  I chose this approach in the interest of minimum drag. (= Photo)

 

Al

 

Subject: [FlyRotary] Re: FW: [FlyRotary] Exhau= st and Muffler designs.

 

 
-----Inline Attachment Follows-----

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

Hi Al.... Very nice installation...

<= /DIV>

 

One question.

 

Does the discharge of the exhaust that close to the prop = transfer any heat to it. I know the duration of the blade passing across th= e exhaust stream is very short and there is alot of air funneling around th= e cowl and diluting the heat but....

Do you see any sign of heat ?

Doe it leave an exhaust stain on the blade/

 

Thanks in advance,



--- On Wed, = 12/9/09, Al Gietzen <ALVentures@cox.net> wrote:


From: Al Gietzen <AL= Ventures@cox.net>
Subject: [FlyRotary] FW: [FlyRotary] Exhaust and Mu= ffler designs.
To: "Rotary motors in aircraft" <flyrotary@lancaironli= ne.net>
Date: Wednesday, December 9, 2009, 10:52 PM

Phil;=

Here is a posting; = with attachments, that I sent to the list about 6 months ago.=

The inconel is .045= or .050=E2=80=9D; I=E2=80=99m not certain which.  The fabricator (Mar= k Sadickas (sp?); referred by Dave Atkins) had the material.  Material= s and labor came to $1950.

 

The secondary muffl= er is .032=E2=80=9D 321SS outside, with through-pipe and ends of .049=E2=80= =9D.  The outside of the secondary stays relatively cool =E2=80=93 I l= earned that the O2 sensor would not get hot enough there to give good readi= ngs, suggesting maybe about 900F.

Al

 

-----Original Message-----
From: Rotary motors in aircraft [mailto:flyr= otary@lancaironline.net] On Behalf Of = Al Gietzen
Sent:<= /B> Sunday, June 08, 2008 = 12:15 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Exhaust and Muffler designs.=

 

Exhaust and muffler design in the rotary i= nstallation is one of the more complex of all the installation issues. Ther= e are, and have been so many variations among the various installations tha= t there is little statistical proof of anything.  I=E2=80=99ll add a f= ew comments and opinions that may be relevant, and describe what I did. It = may trigger some ideas for you to think about. My system on the 20B is now = approaching 100 hours =E2=80=93 not a long term proof =E2=80=93 but it is s= till solid.

 

The exhaust temps out of the port are very= high, typically in the neighborhood of 1600F, and sometimes maybe 1700F.&n= bsp; Couple this with pressure pulses and vibrational loads, and corrosive = environment, and you have a very demanding situation.  When you look a= t material properties to handle this, things narrow down pretty rapidly, pa= rticularly if you also want light weight as we do in aviation.  Stainl= ess steels, like 321, can handle the temps and be a workable exhaust =E2=80= =93 but, design for low stress levels then becomes a must, because SS are s= ubject to =E2=80=98stress corrosion=E2=80=99 at these temps.  Combine = the high temperatures and vibrational stress and you get inter-granular cor= rosion which weakens the material and it eventually falls apart.

 

On way to alleviate that is to use inconel= .  It gives you higher temperature capability and corrosion resistance= .  And it gives you higher cost.  But is it worth it to reduce yo= ur risk a forced landing in an unfriendly place?  Compared to the tota= l cost of your airplane it=E2=80=99s a small amount.  Maybe cut cost s= omewhere where it is less critical to safety.

 

Another thing to consider is that the more= quickly you can expand the exhaust gas, the more quickly you can deal with= lower temperatures.  Charles Law =E2=80=93 temp (degree K) goes down = in direct proportion to increased volume.  This becomes more complex i= n an exhaust system because of other factors, but it still works in your fa= vor.  The gas will expand down a constant diameter pipe, but expanding= into a BIG pipe can make a significant drop.  

 

That can be one of the advantages of the t= angential muffler/manifold, or the design that Neil presented.  The am= ount of the temp drop of course depends on the pressure in that bigger can.= These designs have their own possible failure modes associated with welded= joints and thermal stresses, but at least there is nothing there that is g= oing to plug up the flow downstream.  The skill of the welder and the = post-weld heat treatment are important factors.

 

These units are generally bolted directly = to the engine via the short header pipes, so vibration loads are a factor. = Ideally you=E2=80=99d like to have stress (and thermal expansion) de-coupli= ng between the engine and the muffler/manifold, but since the engine can mo= ve relative to it=E2=80=99s mount you either have to accommodate significan= t movement, or support it to the engine by some other means then the header= pipes.

 

And then there is the matter of the exit p= ipe(s) and secondary mufflers. Those have to be supported as well =E2=80=93= an unsupported length of pipe extending from the muffler is an ideal candi= date for some vibrational resonance which will fail the system somewhere. A= nd the further away from the engine centerline, the greater the loads.

 

My exhaust system is shown in the first at= tached photo. This is in a pusher configuration.  It is an inconel tan= gential manifold/muffler supported to the engine by short inconel header pi= pes which are welded to a heavy RB steel flange. It has a convex =E2=80=98h= ead=E2=80=99 at the front, and a conical outlet to the exit pipe.  It = has internal vanes welded at an angle on the inside surface opposite the ex= it from the headers (you can see the welds on the outside) to help break up= the pulses and direct the exhaust toward the exit. They also prevent possi= ble =E2=80=9Cswirl-flow choking=E2=80=9D which could increase back pressure= .  There are =E2=80=98straightening=E2=80=99 vanes in the conical exit= section.

 

The exit pipe is clamped (custom heavy SS = clamp) to the inlet pipe of the secondary muffler (I=E2=80=99ll call it a r= esonator).  The resonator is also of my design and is made of 321 SS.&= nbsp; It is basically a straight through 2 =C2=BE=E2=80=9D pipe that is dri= lled full of =C2=BC=E2=80=9D holes (about 100), contained within outer 5=E2= =80=9D dia. pipe.  The inner pipe has an orifice plate at the center w= hich has a 1 5/8=E2=80=9D opening.  This orifice produces some restric= tion to the flow through the resonator to force some of it outward through = the holes, and back through the holes to exit.  The purpose of the res= onator is to knock down the pressure peaks a bit more.  Measurements o= n the dyno showed that resonator knocked another 8 db off the sound level a= nd had no noticeable effect on the HP.

 

The plug in the resonator closes a port or= iginally intended for the O2 sensor. But it didn=E2=80=99t work well in tha= t location because the temperature was too low (interesting, huh). I had to= move it to the inlet pipe.

 

Last but not least, there is a SS support = at the end which clamps solidly to the redrive. The clamp is designed to be= rigid laterally, but to also be an effective heat choke.  This suppor= ts the resonator, and reduces the likelihood of any resonance vibration in = the system.

 

I originally thought that the resonator in= ternals may not last more than 50 hours, but at 95 hours they are still sol= id. Which brings up another point.  It is easily inspected. I can see = those internals from the exit end, and I can stick a screwdriver or ratchet= handle or whatever; in there and bang around to be sure things are sound. =  I inspect all the welds in the exhaust system every time I remove the= cowl, or at least every 10 hours or so.  Make your system inspectable= , and keep an eye on it.

 

I wouldn=E2=80=99t call it =E2=80=9Cquiet= =E2=80=9D, but I=E2=80=99ve had people say they like the way it sounds. Tim= e will tell its reliability.

 

Best,

 

Al Gietzen

 

 

       &n= bsp;    If you go through the archives, you'll find lots of = examples of

failed muffler designs.  Many by your's= truly.  I think I've tried every

concoction known to man and the Swiss. = They all worked...  for a while. 

       &n= bsp;    My best overall design (see attached) is a 2" tube, = full of holes

inside a 5" tube.  All made of 16ga SS,= all welded together.  Needless to

say, the flange is more like 3/16" - 1/4" SS= .  The inside end of the 2" tube

is welded to the end cap of the 5" tube.&nbs= p; That blocks off the one end of the

2" tube and secures it from movement.  = The exhaust end of the 2" tube is

welded through a 2" hole in the other 5" end= cap.  Rather than drilling the

2" tube full of round holes, we cut slots wi= th a saw.  Then take a big flat

blade screwdriver, stick it in the slot and = bend it over.  This creates an

oblong hole.  (Much easier than drillin= g into SS.  This is what will go on

the Volmer.

 

       &n= bsp;    The sound is quite acceptable, it fits inside the co= wl and Jim M.'s

version lasted the life of the aircraft... 6= 00+ hours.

 

Neil

 

PS: Are you considering Rough = River?

 

 

 

-----Original Message-----

From: Rotary motors in aircraft [mailto:flyr= otary@lancaironline.net] On

Behalf Of Al Wick

Sent: Saturday, June 07, 2008 = 4:57 PM

To: Rotary motors in aircraft<= /DIV>

Subject: [FlyRotary] Re: Mistral Crash Analy= sis

 

C'mon guys. You do this every time there's a= crash. Instantly go into

rationalization mode. It's unhealthy. Greatl= y increases risk builders won't

take action. Increases risk you won't resear= ch it thoroughly.

 

A healthy response would be:" Here's another= example of how our engines

produce unusually destructive exhaust temper= ature and pulses. We have a rich

 

history of broken exhaust components. We nee= d to be very thorough when

designing and building exhaust."

 

I designed my own muffler. It had two inlets= , two outlets. So if (when) my

muffler failed, it could never block both pi= pes. I also put loose safety

wire around my pipes, because on a pusher lo= osing pipe wipes out prop. So

basically, I assume stuff will  fail, t= hen design it to control the way it

fails. I've heard of rotary guys doing same = type of thing. This is a good

time to share those key items.=

 

On your car, they deliberately design produc= ts to fail a certain way. They

will make a component weak, so it fails firs= t. They do that with wheels and

hubs. So when the muffler fails, little piec= es come apart, not big sections?

 

You guys do a great job of sharing successes= , design and construction

details. This is another opportunity.=

 

-al wick

 

 

 

 

<No doubt you are on the money, Rusty.&nb= sp; When folks are already predisposed

to bad mouth the rotary - this will only be = more ammunition.  "See! even

with umpteen million dollars you can't get o= ne to fly"  {:>).  But, I

serious doubt it will effect many who have r= esearched the rotary and come to

 

understand its benefits - as for the rest, w= ho cares {:>)

>

 

  I'm certain it was a relief to Mistra= l that the culprit was not one of

their engine components.

 

 

 

  Whew! a close one for sure.

 

 

 

  Hi Ed,

 

 

 

  Unfortunately, I bet the majority of = people will only hear "Mistral

rotary", "lost power", and "crash"  :-(=

 

 

 

  Rusty (RV-3 taking forever.)

 

____________________________________________= ________________

Orlando Vacations - Click Here= !

http://thirdpartyoffers.juno.com/TGL2141/fc/= Ioyw6i3nK7u59LkagfZ5IcEgGqYcvPRC

wA85GgQITbFK9vE7wPGKFP/

 

--

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