X-Virus-Scanned: clean according to Sophos on Logan.com X-SpamCatcher-Score: 2 [X] Return-Path: Received: from ispmxmta06-srv.windstream.net ([166.102.165.167] verified) by logan.com (CommuniGate Pro SMTP 5.1.8) with ESMTP id 2052260 for flyrotary@lancaironline.net; Fri, 18 May 2007 17:55:38 -0400 Received-SPF: pass receiver=logan.com; client-ip=166.102.165.167; envelope-from=montyr2157@alltel.net Received: from ispmxaamta05-gx.windstream.net ([162.40.59.162]) by ispmxmta06-srv.windstream.net with ESMTP id <20070518215459.TXJJ718.ispmxmta06-srv.windstream.net@ispmxaamta05-gx.windstream.net> for ; Fri, 18 May 2007 16:54:59 -0500 Received: from Thorstwin ([162.40.59.162]) by ispmxaamta05-gx.windstream.net with SMTP id <20070518215459.ULUM3772.ispmxaamta05-gx.windstream.net@Thorstwin> for ; Fri, 18 May 2007 16:54:59 -0500 Message-ID: <000601c79997$388d6350$6401a8c0@Thorstwin> From: "M Roberts" To: "Rotary motors in aircraft" Subject: Exhaust Ideas Date: Fri, 18 May 2007 16:55:16 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0003_01C7996D.4F689F10" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.3028 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3028 This is a multi-part message in MIME format. ------=_NextPart_000_0003_01C7996D.4F689F10 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Some work has been done to improve the retention of wood props by using = belville washers. The wood expands and contracts with moisture, = requiring periodic torquing of the bolts. Belville washers will keep the = proper tension while allowing a bit of movement from the wood. Would the same technique work to attach a header? Several hundred pounds = of pressure. High enough to keep the header where it belongs and keep = exhaust gas from blowing through, but low enough to allow some thermal = variance? Ernest, If you had a slot in the flange running horizontally or a loose = clearance hole instead of a tight clearance hole, it might work. I say = might because we are dealing with what has more friction, the washer on = the flange or the gasket on the flange.=20 The wood prop is a different load case. Involving axial loading of the = stud. The wood gets crushed by the washer when the wood swells, then = when it contracts the nut comes loose. In the header case the separate = flanges load the studs in bending, a condition which is very bad for a = fastener with threads on it in a thermally cycled, corrosive = environment. All ugly from a fatigue standpoint. I would personally not want the flange working on the gasket or the = stud. Best to put a slip joint in the header, clamp the flange and = gasket down tight and solve the problem for sure. Monty ------=_NextPart_000_0003_01C7996D.4F689F10 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Some work has=20 been done to improve the retention of wood props by using belville = washers. The=20 wood expands and contracts with moisture, requiring periodic torquing of = the=20 bolts. Belville washers will keep the proper tension while allowing a = bit of=20 movement from the wood.

Would the same technique work to attach a = header?=20 Several hundred pounds of pressure. High enough to keep the header where = it=20 belongs and keep exhaust gas from blowing through, but low enough to = allow some=20 thermal variance?
 
Ernest,
 
If you had a slot in the flange running = horizontally or a loose clearance hole instead of a tight clearance = hole, it=20 might work. I say might because we are dealing with what has more = friction, the=20 washer on the flange or the gasket on the flange.
 
The wood prop is a different load case. = Involving=20 axial loading of the stud. The wood gets crushed by the washer = when the=20 wood swells, then when it contracts the nut comes loose. In the = header case=20 the separate flanges load the studs in bending, a condition which = is very=20 bad for a fastener with threads on it in a thermally cycled, corrosive=20 environment. All ugly from a fatigue standpoint.
 
I would personally not want the flange = working on=20 the gasket or the stud. Best to put a slip joint in the header, clamp = the flange=20 and gasket down tight and solve the problem for = sure.
 
Monty
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