X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Fri, 06 Oct 2006 23:17:07 -0400 Message-ID: X-Original-Return-Path: Received: from tomts20-srv.bellnexxia.net ([209.226.175.74] verified) by logan.com (CommuniGate Pro SMTP 5.1c.5) with ESMTP id 1446034 for lml@lancaironline.net; Fri, 06 Oct 2006 10:25:21 -0400 Received-SPF: pass receiver=logan.com; client-ip=209.226.175.74; envelope-from=ian.crowe@sympatico.ca Received: from userehlq54l0us ([69.159.71.49]) by tomts20-srv.bellnexxia.net (InterMail vM.5.01.06.13 201-253-122-130-113-20050324) with SMTP id <20061006142500.TLVM16051.tomts20-srv.bellnexxia.net@userehlq54l0us> for ; Fri, 6 Oct 2006 10:25:00 -0400 X-Original-Message-ID: <001801c6e952$f183e1e0$0a02a8c0@userehlq54l0us> From: "Ian Crowe" X-Original-To: "Lancair Mailing List" Subject: Torque specs X-Original-Date: Fri, 6 Oct 2006 08:23:07 -0600 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0015_01C6E920.A6CDFAA0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2869 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.2962 This is a multi-part message in MIME format. ------=_NextPart_000_0015_01C6E920.A6CDFAA0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable In large diesel engines (3000hp) on the connecting rod bolts the bolt = stretch method is often used. This involved measuring the bolt free = length and then applying the bolt and tightening to reach a = predetermined bolt stretch. It was then pinned and that was that. = Difficult to do inside the small openings available to us on our = engines. Also the bolt head and end had a machined surface to = facilitate measurement. If you are worried about the resistance of the stop nut or self locking = nut you can always use a castellated nut and split pin or the double = lock nut method. You do have a valid point there and maybe one of our = AME correspondents can enlighten us as to what the correct practice is = in the aviation world. The important things to look at when using bolts is that the amount of = preload on the bolt will prevent the bolt being subject to reversing = stress cycles, thereby avoiding fatigue and fracture. The other = important point is that the mating surfaces being clamped must be in = full contact with each other to avoid flexing which could cause the = stress reversal. This is for tensile loading. If the bolt is in shear = then a different calculation is involved to size the bolt and the = tensile loading of the bolt is secondary to the shear resistance. = Torque is important to load the bolt and keep the surfaces firmly in = contact with each other to assist the shear resistance of the bolt. Ian B. Crowe LNC 2 C-FKRO ------=_NextPart_000_0015_01C6E920.A6CDFAA0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

In large diesel engines (3000hp) on the = connecting=20 rod bolts the bolt stretch method is often used. This = involved=20 measuring the bolt free length and then applying the bolt and tightening = to=20 reach a predetermined bolt stretch. It was then pinned and that = was=20 that. Difficult to do inside the small openings available to us on = our=20 engines. Also the bolt head and end had a machined surface to = facilitate=20 measurement.

If you are worried about the resistance = of the stop=20 nut or self locking nut you can always use a castellated nut and split = pin or=20 the double lock nut method. You do have a valid point there and = maybe one=20 of our AME correspondents can enlighten us as to what the correct = practice is in=20 the aviation world.

The important things to look at when = using bolts is=20 that the amount of preload on the bolt will prevent the bolt being = subject to=20 reversing stress cycles, thereby avoiding fatigue and fracture. = The other=20 important point is that the mating surfaces being clamped must be in = full=20 contact with each other to avoid flexing which could cause the stress=20 reversal. This is for tensile loading. If the bolt is in = shear then=20 a different calculation is involved to size the bolt and the tensile = loading of=20 the bolt is secondary to the shear resistance. Torque is important = to load=20 the bolt and keep the surfaces firmly in contact with each other = to assist=20 the shear resistance of the bolt.

Ian B. Crowe
LNC 2 = C-FKRO

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