X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from mx2.netapp.com ([216.240.18.37] verified) by logan.com (CommuniGate Pro SMTP 5.3.5) with ESMTPS id 4218410 for flyrotary@lancaironline.net; Mon, 12 Apr 2010 09:01:03 -0400 Received-SPF: softfail receiver=logan.com; client-ip=216.240.18.37; envelope-from=echristley@nc.rr.com X-IronPort-AV: E=Sophos;i="4.52,190,1270450800"; d="scan'208";a="343190264" Received: from smtp1.corp.netapp.com ([10.57.156.124]) by mx2-out.netapp.com with ESMTP; 12 Apr 2010 06:00:11 -0700 Received: from [10.62.16.54] (ernestc-laptop.hq.netapp.com [10.62.16.54]) by smtp1.corp.netapp.com (8.13.1/8.13.1/NTAP-1.6) with ESMTP id o3CD0Arb022986 for ; Mon, 12 Apr 2010 06:00:10 -0700 (PDT) Message-ID: <4BC31955.9080307@nc.rr.com> Date: Mon, 12 Apr 2010 09:00:05 -0400 From: Ernest Christley Reply-To: echristley@nc.rr.com User-Agent: Thunderbird 2.0.0.24 (X11/20100317) MIME-Version: 1.0 To: Rotary motors in aircraft Subject: Re: [FlyRotary] Re: Tangential muffler References: In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Mark Steitle wrote: > Kelly, > > The really nice thing about the slotted tube is that anyone with a > side grinder and a hammer could build it. I cut the outer tube with a > chop saw. Used a side grinder & die grinder for shaping the inlets, > etc. I purchased all of the materials off ebay. The muffler shop > expanded some of the misc pieces used for the joints. So, this is a > project that almost anyone could accomplish with basic tools (welding > excluded). The difficult part (for me) was deciding on the design. > > Mark Do you have a way to inspect the inner tube, Mark? A grinder will leave two fairly severe 90 degree corners on every edge of the cut slot. Compounding this is the fact that the side grinder cuts a circle. The end of each slot will be left with a knife edge profile pointing back toward the slot. This will create some mean stress risers. The expectation is that this tube is to live in an environment that has to be the closest thing to hell on Earth we could imagine (extreme heat and constant sonic blasts). I would have suggested drilling 3/16" holes and connecting them with the grinder. Unless the inside tube is fabricated different than what I understand, I can't help but to think that it will have a very short life. Cracks will start in the corners of each slot, and the tube will disintegrate. Can it be easily pulled apart so that you could run a round needle file down both sides of all the slots to round them out?