X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fed1rmmtao106.cox.net ([68.230.241.40] verified) by logan.com (CommuniGate Pro SMTP 5.3c2) with ESMTP id 3976974 for flyrotary@lancaironline.net; Sun, 15 Nov 2009 12:23:29 -0500 Received-SPF: none receiver=logan.com; client-ip=68.230.241.40; envelope-from=rv-4mike@cox.net Received: from fed1rmimpo02.cox.net ([70.169.32.72]) by fed1rmmtao106.cox.net (InterMail vM.8.00.01.00 201-2244-105-20090324) with ESMTP id <20091115172255.YQCF21192.fed1rmmtao106.cox.net@fed1rmimpo02.cox.net> for ; Sun, 15 Nov 2009 12:22:55 -0500 Received: from wills ([68.105.88.66]) by fed1rmimpo02.cox.net with bizsmtp id 5VNt1d0051RtBmC04VNvgG; Sun, 15 Nov 2009 12:22:55 -0500 X-VR-Score: 0.00 X-Authority-Analysis: v=1.0 c=1 a=qq9DRYpwRrkA:10 a=ayC55rCoAAAA:8 a=5mjRlV6LAAAA:8 a=7g1VtSJxAAAA:8 a=Ia-xEzejAAAA:8 a=dAmBKRgsrcm3Mji1KZ0A:9 a=j2NV0b6481EOfZXW_P8A:7 a=2GxERWWk3IX2B_SzQCAzebqdRmQA:4 a=RRkQmeXyBBsA:10 a=54jd_EiB-BMA:10 a=JATu0hzrejUA:10 a=dHuparDFRF4A:10 a=pGLkceISAAAA:8 a=d_ybYVMely5iwES-ccwA:9 a=-ly-fAE094wXZwQGcHIA:7 a=OyzaV6i6berFQbpIVrfobdNNWMYA:4 a=MSl-tDqOz04A:10 a=EzXvWhQp4_cA:10 X-CM-Score: 0.00 Message-ID: From: "Mike Wills" To: "Rotary motors in aircraft" References: Date: Sun, 15 Nov 2009 09:22:54 -0800 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0026_01CA65D5.36042080" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.5843 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579 Subject: Re: [FlyRotary] Re: Phononic bandgap muffler This is a multi-part message in MIME format. ------=_NextPart_000_0026_01CA65D5.36042080 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable For the time being I've decided to deal with it by using a better = headset and making the rest of the world live with it. But I'm anxiously = waiting for the time when somebody takes all of the theoretical stuff, = builds a real muffler, and bolts it onto a screaming rotary to test it = against a known benchmark. My plate is full just getting my Phase 1 = testing done and I dont want to sidetrack that with a bunch of = testing/experimenting. But I'd be willing to provide my DNA muffler as = the benchmark if someone is willing to step up and do this testing. Off topic. Did a little data gathering yesterday to verify performance = of my airspeed/static system. Flew the 4 leg course described by Doug = Grey in a recent Kitplanes article and plugged the numbers into the = spreadsheet provided in that article. Looks like my airspeed indicator = and static system are performing well, at least at the 75% cruise = condition. At 8500' and full throttle I'm getting 191 MPH TAS. This = lines up pretty well with Van's book number for a 160HP Lyc and = definitely exceeds the performance of my old RV-6A. Mike Wills RV-4 N144MW ----- Original Message -----=20 From: Mark Steitle=20 To: Rotary motors in aircraft=20 Sent: Sunday, November 15, 2009 5:46 AM Subject: [Norton AntiSpam] [FlyRotary] Re: Phononic bandgap muffler Ernest,=20 This is very interesting and applicable to every rotary installation. = Sooner or later everyone must deal with the exhaust noise one way or = another. For me, I'm waiting to hear more (no pun intended) about your = experiments. Mark S. On Sat, Nov 14, 2009 at 11:37 PM, Ernest Christley = wrote: Here's a question for you audiophiles on the list. How much effort = is 10dB of muffling worth? I've expanded on my experiments with phononic bandgap filters, and I = think I've fairly conclusively demonstrated up to 15dB of attenutation = in the frequency ranges between 8kHz and 12kHz. I used the run-up video = that Mike Wills provided for us a few weeks back (thanks Mike), and I = was a little more methodical than last time. For those that don't remember, a phononic bandgap filter is created = by geometric arrangement of dissimillar materials, with the goal of = filtering specific vibration frequencies. It appears that 1/2" diameter = tubes, arranged in a grid with 1" centers does a nice job of attenuating = frequencies in the 8kH to 12kHz range.=20 I set up my simulated muffler...a wooden shell with PVC filter = elements. I stuck a couple speakers in the inlet side, and a = microphone on the outlet side. In this setup, there is going to be all = sorts of losses from the conversion from an electronic signal to sound = in the speaker, then conversion of sound to an electronics signal in the = microphone. Comparing the original to the recorded muffled sound, which = I did in the first experiment, is not valid. What I did this time instead, is to compare several recordings. = Each with one less row of filter elements than the last, until I was = measuring an empty box. The empty box measurement is the control that = lets me know if I'm doing anything with the array of tubes. What I = found was that each row of tubes provide a significant attenuation in = the frequencies between 8kHz and 12kHz. The ones that give us the = weed-wacker sound. I determined this by taking a time sample across = each of the 5 recordings and having Audacity plot the spectrum. I have an xcf file created by The Gimp ( a free image editing = software). The xcf format allows you to keep an image in layers. Each = of the plots is in a separate layer, and by playing with the opacity = individual layers, you can easily see where the attenuation occurs. The = file is 465kB so I can't post it to the list, but if anyone is = interested, I'll be happy to send it direct. I'll do a writeup with = links to the audio files "real soon now".=20 I have attached a flatten image showing the 0 row run, against the 4 = row run. The 0 run is the lighter purple shade. There are some some = frequencies where the 4 row would be louder....around 4kHz and 7kHz, = but I think the attenuation of those frequencies around 10kHz would be = most beneficial. --=20 Ernest Christley, President Ernest@TechnicalTakedown.com TechnicalTakedown, LLC www.TechnicalTakedown.com 101 Steep Bank Dr. Cary, NC 27518 (919) 741-9397 -- Homepage: http://www.flyrotary.com/ Archive and UnSub: = http://mail.lancaironline.net:81/lists/flyrotary/List.html ------=_NextPart_000_0026_01CA65D5.36042080 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
For the time being I've decided to deal = with it by=20 using a better headset and making the rest of the world live with it. = But I'm=20 anxiously waiting for the time when somebody takes all of the = theoretical stuff,=20 builds a real muffler, and bolts it onto a screaming rotary to test it = against a=20 known benchmark. My plate is full just getting my Phase 1 testing done = and I=20 dont want to sidetrack that with a bunch of testing/experimenting. But = I'd be=20 willing to provide my DNA muffler as the benchmark if someone is willing = to step=20 up and do this testing.
 
Off topic. Did a little data gathering = yesterday to=20 verify performance of my airspeed/static system. Flew the 4 leg course = described=20 by Doug Grey in a recent Kitplanes article and plugged the numbers into = the=20 spreadsheet provided in that article. Looks like my airspeed = indicator and=20 static system are performing well, at least at the 75% cruise condition. = At=20 8500' and full throttle I'm getting 191 MPH TAS. This lines up pretty = well with=20 Van's book number for a 160HP Lyc and definitely exceeds the performance = of my=20 old RV-6A.
 
Mike Wills
RV-4 N144MW
----- Original Message -----
From:=20 Mark = Steitle=20
Sent: Sunday, November 15, 2009 = 5:46=20 AM
Subject: [Norton AntiSpam] = [FlyRotary]=20 Re: Phononic bandgap muffler

Ernest,
 
This is very interesting and applicable to every rotary=20 installation.  Sooner or later everyone must deal with the = exhaust noise=20 one way or another.  For me, I'm waiting to hear more (no pun = intended)=20 about your experiments.
 
Mark S.

On Sat, Nov 14, 2009 at 11:37 PM, Ernest = Christley=20 <echristley@nc.rr.com> = wrote:
Here's=20 a question for you audiophiles on the list.  How much effort is = 10dB of=20 muffling worth?

I've expanded on my experiments with phononic = bandgap=20 filters, and I think I've fairly conclusively demonstrated up to = 15dB of=20 attenutation in the frequency ranges between 8kHz and 12kHz.  I = used=20 the run-up video that Mike Wills provided for us a few weeks back = (thanks=20 Mike), and I was a little more methodical than last time.

For = those=20 that don't remember, a phononic bandgap filter is created by = geometric=20 arrangement of dissimillar materials, with the goal of filtering = specific=20 vibration frequencies.  It appears that 1/2" diameter tubes, = arranged=20 in a grid with 1" centers does a nice job of attenuating frequencies = in the=20 8kH to 12kHz range.
I set up my simulated muffler...a wooden = shell with=20 PVC filter elements.   I stuck a couple speakers in the inlet = side, and=20 a microphone on the outlet side.  In this setup, there is going = to be=20 all sorts of losses from the conversion from an electronic signal to = sound=20 in the speaker, then conversion of sound to an electronics signal in = the=20 microphone.  Comparing the original to the recorded muffled = sound,=20 which I did in the first experiment, is not valid.

What I did = this=20 time instead, is to compare several recordings.  Each with one = less row=20 of filter elements than the last, until I was measuring an empty = box.=20  The empty box measurement is the control that lets me know if = I'm=20 doing anything with the array of tubes.  What I found was that = each row=20 of tubes provide a significant attenuation in the frequencies = between 8kHz=20 and 12kHz.  The ones that give us the weed-wacker sound. =  I=20 determined this by taking a time sample across each of the 5 = recordings and=20 having Audacity plot the spectrum.

I have an xcf file created = by The=20 Gimp ( a free image editing software).  The xcf format allows = you to=20 keep an image in layers.  Each of the plots is in a separate = layer, and=20 by playing with the opacity individual layers, you can easily see = where the=20 attenuation occurs.  The file is 465kB so I can't post it to = the list,=20 but if anyone is interested, I'll be happy to send it direct. =  I'll do=20 a writeup with links to the audio files "real soon now".
I have = attached=20 a flatten image showing the 0 row run, against the 4 row run. =  The 0=20 run is the lighter purple shade.  There are some some = frequencies where=20 the  4 row would be louder....around  4kHz and 7kHz, but I = think=20 the attenuation of those frequencies around 10kHz would be most=20 beneficial.

--
Ernest Christley,=20 President
Ernest@TechnicalTakedown.com

TechnicalTakedown,=20 LLC
www.TechnicalTakedown.com
101 Steep Bank = Dr.
Cary,=20 NC  27518
(919) 741-9397


--
Homepage:  http://www.flyrotary.com/
Archive and UnSub: =   http://mail.lancaironline.net:81/lists/flyrotary/List.htm= l


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