X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from cdptpa-omtalb.mail.rr.com ([75.180.132.121] verified) by logan.com (CommuniGate Pro SMTP 5.2.11) with ESMTP id 3416305 for flyrotary@lancaironline.net; Thu, 08 Jan 2009 07:49:38 -0500 Received-SPF: pass receiver=logan.com; client-ip=75.180.132.121; envelope-from=eanderson@carolina.rr.com Received: from computername ([75.191.186.236]) by cdptpa-omta02.mail.rr.com with ESMTP id <20090108124900.JKBV73.cdptpa-omta02.mail.rr.com@computername> for ; Thu, 8 Jan 2009 12:49:00 +0000 From: "Ed Anderson" To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Re: FAW and the Phonoic gap [FlyRotary] Re: Muffler design (was 20B isssues . . ) Date: Thu, 8 Jan 2009 07:49:10 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0018_01C97165.97D45380" X-Mailer: Microsoft Office Outlook, Build 11.0.5510 In-Reply-To: Thread-Index: AclxTUWMb7BzF4/fSC+bOpU5or2ZvQAQgl+Q X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579 Message-Id: <20090108124900.JKBV73.cdptpa-omta02.mail.rr.com@computername> This is a multi-part message in MIME format. ------=_NextPart_000_0018_01C97165.97D45380 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Actually, Excel sort of choke on it {:>) Ed Ed Anderson Rv-6A N494BW Rotary Powered Matthews, NC eanderson@carolina.rr.com http://www.andersonee.com http://members.cox.net/rogersda/rotary/configs.htm#N494BW http://www.dmack.net/mazda/index.html _____ From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Bob Perkinson Sent: Wednesday, January 07, 2009 11:54 PM To: Rotary motors in aircraft Subject: [FlyRotary] Re: FAW and the Phonoic gap [FlyRotary] Re: Muffler design (was 20B isssues . . ) Ed, You ought a be able to load that into Excel and crank out muffler dimensions for any airplane {:>) That is what it does ant it??? All this is well over my head... Bob. -------------- Original message from "Ed Anderson" : -------------- > Ernest, keep in mind that the results you get with your sound recording may > not be indicative of what real exhaust pulse would give you. The reason > -the exhaust pulse is a Finite Amplitude Wave - and they do behave > differently in reflecting and refracting than standard sound waves. > > The math is not too intimidating {:>) > > http://www.wikiwaves.org/index.php/Finite_Amplitude_Wave_Theory > > > > Ed Anderson > > Rv-6A N494BW Rotary Powered > > Matthews, NC > > eanderson@carolina.rr.com > > http://www.andersonee.com > > http://members.cox.net/rogersda/rotary/configs.htm#N494BW > > http://www.dmack.net/mazda/index.html > > -----Original Message----- > From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On > Behalf Of Ernest Christley > Sent: Wednesday, January 07, 2009 4:07 PM > To: Rotary motors in aircraft > Subject: [FlyRotary] Re: Muffler design (was 20B isssues . . ) > > Tracy Crook wrote: > > Agreed, this is definitely a new concept and I hope it works. > > > > The only thing that bothers me is that, as you pointed out, the > > bandwidth needed for attenuation is about 0 to 12 Khz. That > > represents MANY octaves even if we bump the lower limit to a realistic > > number ( only a closed pipe will work at zero :-). This bandwidth is > > mutually exclusive with the term "tuned". And if by tuned they mean > > low pass, then it is not a new concept since that is covered by > > conventional mufflers. There may be something to this new concept but > > until this contradiction is explained, I would hesitate to start > > cutting parts. > The first parts I'm going to cut are wood sides and PVC pipe baffles. > That'll be good enough to experiment with. I've got a sound sample of a > frequency sweep. I can build a test muffler, play the frequency sweep > in one end, and record it on the other. Displaying both samples in a > sound editor will tell me what, if any, frequencies are attenuated, and > by how much. Losses in the playback speakers and microphone can be > documented by running a test without the intervening muffler. I may > have to spend money on good speakers and a good microphone (Oh, > bummer!). If that shows promise, I replace the PVC with stainless > tubes. If that works, I replace the wood with stainless sheet. > > Which frequencies need to be attenuated? Remember that Monty Roberts > did some work a while back showing a sonagram of a rotary recording? > The sound energies are much higher around 6 and 12kHz. With that in > mind, look at the graphs on the top of page 4 of this report > http://web.mit.edu/course/3/3.042/team1_08f/documents/complete-phononic-band > gap.pdf > > It shows very significant attenuation in frequencies from 4 to 8kHz and > then 10 to 14kHz. This is with 13mm cylinders set in a 30mm square > array. Hollow cylinders showed similar efficacy. Close enough to 1/8" > pipe (mcmaster-carr part# 44635K422 ... cheap!) to make a prototype > almost mandatory. So, my current plan of action is to produce some > sonagrams of rotary exhaust noise, and verify the target frequencies for > attenuation. With the experimental jig, optimize for bandgaps around > those frequencies while using the smallest filling fraction possible. > At that point, I will build a matching prototype. Two sections of steal > sheet, match drilled with 1/2" holes (or whatever size was found to be > optimum). Fill the holes with 3" sections of tube. A bunch of welding > later, a 8.5" wide muffler with a .500 filling fraction will render > about the same flow area as a 4" diameter exhaust pipe. > > -- > Homepage: http://www.flyrotary.com/ > Archive and UnSub: > http://mail.lancaironline.net:81/lists/flyrotary/List.html > > __________ Information from ESET NOD32 Antivirus, version of virus signature > database 3267 (20080714) __________ > > The message was checked by ESET NOD32 Antivirus. > > http://www.eset.com > > > > __________ Information from ESET NOD32 Antivirus, version of virus signature > database 3267 (20080714) __________ > > The message was checked by ESET NOD32 Antivirus. > > http://www.eset.com > > > > -- > Homepage: http://www.flyrotary.com/ > Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html __________ Information from ESET NOD32 Antivirus, version of virus signature database 3267 (20080714) __________ The message was checked by ESET NOD32 Antivirus. http://www.eset.com ------=_NextPart_000_0018_01C97165.97D45380 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Actually, Excel sort of choke on it {:>)

 

Ed

 

Ed Anderson

Rv-6A N494BW Rotary = Powered

Matthews, NC

eanderson@carolina.rr.com=

http://www.andersonee.com

http://members.cox.net/rogersda/rotary/configs.htm#N494BW

http://www.dmack.net/mazda/index.html<= font size=3D2 face=3DArial>

From: = Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Bob Perkinson
Sent: Wednesday, January = 07, 2009 11:54 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: = FAW and the Phonoic gap [FlyRotary] Re: Muffler design (was 20B isssues . . = )

 

Ed,
You ought a be able to load that into Excel and crank out muffler = dimensions for any airplane {:>) That is what it does ant it???
All this is well over my head...
Bob.

-------------- Original message from "Ed Anderson" <eanderson@carolina.rr.com>: --------------


> Ernest, keep in mind that the results you get with your sound = recording may
> not be indicative of what real exhaust pulse would give you. The = reason
> -the exhaust pulse is a Finite Amplitude Wave - and they do behave =
> differently in reflecting and refracting than standard sound waves. =
>
> The math is not too intimidating {:>)
>
> http://www.wikiwaves.org/index.php/Finite_Amplitude_Wave_Theory =
>
>
>
> Ed Anderson
>
> Rv-6A N494BW Rotary Powered
>
> Matthews, NC
>
> eanderson@carolina.rr.com
>
> http://www.andersonee.com
>
> http://members.cox.net/rogersda/rotary/configs.htm#N494BW
>
> http://www.dmack.net/mazda/index.html
>
> -----Original Message-----
> From: Rotary motors in = aircraft [mailto:flyrotary@lancaironline.net] On
> Behalf Of Ernest Christley
> Sent: Wednesday, January 07, 2009 4:07 PM
> To: Rotary motors in = aircraft
> Subject: [FlyRotary] Re: Muffler design (was 20B isssues . . )
>
> Tracy Crook wrote:
> > Agreed, this is definitely a new concept and I hope it works. =
> >
> > The only thing that bothers me is that, as you pointed out, = the
> > bandwidth needed for attenuation is about 0 to 12 Khz. That =
> > represents MANY octaves even if we bump the lower limit to a realistic
> > number ( only a closed pipe will work at zero :-). This = bandwidth is
> > mutually exclusive with the term "tuned". And if by = tuned they mean
> > low pass, then it is not a new concept since that is covered = by
> > conventional mufflers. There may be something to this new = concept but
> > until this contradiction is explained, I would hesitate to = start
> > cutting parts.
> The first parts I'm going to cut are wood sides and PVC pipe = baffles.
> That'll be good enough to experiment with. I've got a sound sample = of a
> frequency sweep. I can build a test muffler, play the frequency = sweep
> in one end, and record it on the other. Displaying both samples in = a
> sound editor will tell me what, if any, frequencies are attenuated, = and
> by how much. Losses in the playback speakers and microphone can be =
> documented by running a test without the intervening muffler. I may =
> have to spend money on good speakers and a good microphone (Oh, =
> bummer!). If that shows promise, I replace the PVC with stainless =
> tubes. If that works, I replace the wood with stainless sheet.
>
> Which frequencies need to be attenuated? Remember that Monty = Roberts
> did some work a while back showing a sonagram of a rotary = recording?
> The sound energies are much higher around 6 and 12kHz. With that in =
> mind, look at the graphs on the top of page 4 of this report
> = http://web.mit.edu/course/3/3.042/team1_08f/documents/complete-phononic-b= and
> gap.pdf
>
> It shows very significant attenuation in frequencies from 4 to 8kHz = and
> then 10 to 14kHz. This is with 13mm cylinders set in a 30mm square =
> array. Hollow cylinders showed similar efficacy. Close enough to = 1/8"
> pipe (mcmaster-carr part# 44635K422 ... cheap!) to make a prototype =
> almost mandatory. So, my current plan of action is to produce some =
> sonagrams of rotary exhaust noise, and verify the target = frequencies for
> attenuation. With the experimental jig, optimize for bandgaps = around
> those frequencies while using the smallest filling fraction = possible.
> At that point, I will build a matching prototype. Two sections of = steal
> sheet, match drilled with 1/2" holes (or whatever size was = found to be
> optimum). Fill the holes with 3" sections of tube. A bunch of = welding
> later, a 8.5" wide muffler with a .500 filling fraction will = render
> about the same flow area as a 4" diameter exhaust pipe.
>
> --
> Homepage: http://www.flyrotary.com/
> Archive and UnSub:
> http://mail.lancaironline.net:81/lists/flyrotary/List.html
>
> __________ Information from ESET NOD32 Antivirus, version of virus signature
> database 3267 (20080714) __________
>
> The message was checked by ESET NOD32 Antivirus.
>
> http://www.eset.com
>
>
>
> __________ Information from ESET NOD32 Antivirus, version of virus signature
> database 3267 (20080714) __________
>
> The message was checked by ESET NOD32 Antivirus.
>
> http://www.eset.com
>
>
>
> --
> Homepage: http://www.flyrotary.com/
> Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html =



__________ Information from ESET NOD32 Antivirus, version of virus = signature database 3267 (20080714) __________

The message was checked by ESET NOD32 Antivirus.

http://www.eset.com

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