X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from is1.mum.edu ([69.18.50.66] verified) by logan.com (CommuniGate Pro SMTP 5.1.12) with ESMTP id 2380457 for flyrotary@lancaironline.net; Wed, 10 Oct 2007 21:44:10 -0400 Received-SPF: none receiver=logan.com; client-ip=69.18.50.66; envelope-from=rob@mum.edu Received: from personnel10 ([10.10.0.196]) by is1.mum.edu (8.13.3+Sun/8.13.3) with SMTP id l9B1hZ8K012347 for ; Wed, 10 Oct 2007 20:43:35 -0500 (CDT) Message-ID: <009801c80ba8$ef1ff780$c4000a0a@personnel10> Reply-To: "Rob" From: "Rob" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Hose clamp myth busters Date: Wed, 10 Oct 2007 20:49:17 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0095_01C80B7F.06130100" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.3138 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3138 This is a multi-part message in MIME format. ------=_NextPart_000_0095_01C80B7F.06130100 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Al, Can you tell me how to properly tighten or what the torque should be on = a good quality hose clamp or a constant torque clamp? This is a question = I have never been able to find the answer. Thanks for your help. Robert Robert Bollinger FM1099 MUM Fairfield IA 52557 (641)472-7000 ex2068 (641)919-3213 cell rob@mum.edu ----- Original Message -----=20 From: Al Gietzen=20 To: Rotary motors in aircraft=20 Sent: Saturday, October 06, 2007 9:19 PM Subject: [FlyRotary] Hose clamp myth busters If those hose clamps are not constant torque clamps, please consider = upgrading them before first flight. They're available from McMaster. =20 Mark; I have no objection to the use constant torque clamps, of course. But = I will express my conclusion/opinion that this clamp thing has been over = sold. Certainly not picking on you, and I know our friend on the other = list makes a big issue of the constant torque clamp. IIRC, the main = point raised was the effect of thermal expansion, more exactly the = differential thermal expansion between the inner metal tube (aluminum in = this case) and the clamp (usually SS). Doing the math will show that = this is less than infinitesimal. The temp change of the coolant may be = about 80 C cold to hot. The clamp heats up maybe 15C less than the = aluminum. Assume a 1 =BD" diameter. So the aluminum expands about = 0.000037" on the diameter while the SS expands only 0.000012"; a huge = difference of 0.000025". I am certain that this effect on the thickness = of the elastomer hose is entirely negligible. And besides, having that = clamp just a wee smidgeon tighter when it is hot and pressurized can't = be a bad thing. Now, it is true that over time the elastomer loses some of its = elasticity, mostly over the first few months, and then very slowly over = the next few years - depending on the type of elastomer, of course. So whether they are regular good quality clamps, properly tightened = (not over-tightened), or constant torque clamps properly tightened; I'd = suggest that the important factors are: re-torque the clamps after a few = weeks or a month of use; use the widest clamp for the diameter, and = consider high quality silicone hose - although contemporary automotive = coolant hose can be expected to last 6 - 9 years. The other thing, of = course, is that on our planes we will probably change out the hoses = every second annual or so anyway. One more thing. Consider putting a Schroeder valve on the system = somewhere so you can easily pressure test the system before you fly (or = before you start your engine), and maybe at annual time. It is so much = easier to deal with any leak while things are cool and on the ground. Sorry; did I go on too longJ? Al G ------=_NextPart_000_0095_01C80B7F.06130100 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Al,
Can you tell me how to properly tighten = or what the=20 torque should be on a good quality hose clamp or a constant torque = clamp? This=20 is a question I have never been able to find the answer. Thanks for your = help.
Robert
 
Robert Bollinger
FM1099 = MUM
Fairfield IA=20 52557
(641)472-7000 ex2068
(641)919-3213 cell
rob@mum.edu
 
----- Original Message -----
From:=20 Al = Gietzen=20
Sent: Saturday, October 06, = 2007 9:19=20 PM
Subject: [FlyRotary] Hose clamp = myth=20 busters

If those hose clamps are not = constant=20 torque clamps, please consider upgrading them before first = flight. =20 They're available from McMaster. 

 

Mark;

 

I have no = objection=20 to the use constant torque clamps, of course.  But I will express = my=20 conclusion/opinion that this clamp thing has been over sold. =  Certainly=20 not picking on you, and I know our friend on the other list makes a = big issue=20 of the constant torque clamp.  IIRC, the main point raised was = the effect=20 of thermal expansion, more exactly the differential thermal expansion = between=20 the inner metal tube (aluminum in this case) and the clamp (usually = SS).=20  Doing the math will show that this is less than = infinitesimal.  The=20 temp change of the coolant may be about 80 C cold to hot.  The = clamp=20 heats up maybe 15C less than the aluminum. Assume a 1 =BD=94 = diameter.  So=20 the aluminum expands about 0.000037=94 on the diameter while the SS = expands only=20 0.000012=94; a huge difference of 0.000025=94.  I am certain that = this effect=20 on the thickness of the elastomer hose is entirely negligible. And = besides,=20 having that clamp just a wee smidgeon tighter when it is hot and = pressurized=20 can=92t be a bad thing.

 

Now, it = is true=20 that over time the elastomer loses some of its elasticity, mostly over = the=20 first few months, and then very slowly over the next few years =96 = depending on=20 the type of elastomer, of course.

 

So = whether they are=20 regular good quality clamps, properly tightened (not over-tightened), = or=20 constant torque clamps properly tightened; I=92d suggest that the = important=20 factors are: re-torque the clamps after a few weeks or a month of use; = use the=20 widest clamp for the diameter, and consider high quality silicone hose = =96=20 although contemporary automotive coolant hose can be expected to last = 6 =96 9=20 years.  The other thing, of course, is that on our planes we will = probably change out the hoses every second annual or so=20 anyway.

 

One more=20 thing.  Consider putting a Schroeder valve on the system = somewhere so you=20 can easily pressure test the system before you fly (or before you = start your=20 engine), and maybe at annual time.  It is so much easier to deal = with any=20 leak while things are cool and on the ground.

 

Sorry; = did I go on=20 too longJ?

 

Al=20 G

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