X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from cdptpa-omtalb.mail.rr.com ([75.180.132.122] verified) by logan.com (CommuniGate Pro SMTP 5.2.14) with ESMTP id 3646489 for flyrotary@lancaironline.net; Mon, 18 May 2009 22:30:22 -0400 Received-SPF: pass receiver=logan.com; client-ip=75.180.132.122; envelope-from=echristley@nc.rr.com Received: from [192.168.0.19] (really [66.57.38.121]) by cdptpa-omta01.mail.rr.com with ESMTP id <20090519022945679.UAWU13751@cdptpa-omta01.mail.rr.com> for ; Tue, 19 May 2009 02:29:45 +0000 Message-ID: <4A1219AC.60103@nc.rr.com> Date: Mon, 18 May 2009 22:30:04 -0400 From: Ernest Christley User-Agent: Thunderbird 2.0.0.19 (X11/20090105) MIME-Version: 1.0 To: Rotary motors in aircraft Subject: Re: [FlyRotary] Re: 20b Exhaust References: In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Tracy Crook wrote: > Your mathematics are sound George and using that approach will > certainly keep back pressure to a minimum. But I think it is doomed to > be noisy. That's just my understanding about how mufflers generally > work and I could be wrong. > During a test of mufflers at a rotary fly-in some years back I was > amazed at how effective the muffler became and how small the power > loss was when we installed a 1" diameter muffler outlet pipe on the > test stand engine (13B). 1" is admittedly too small but we learn by > going to extremes sometimes. > > Tracy > Maybe there is a way to get both. This is the first results from my experiments with bandgap filters that I just did today. http://ernest.isa-geek.org/Delta/Experiments/PhononicBandgapFilter.html