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Message-ID: <5cf132c0710070433i694466dcjb1ac53bcded86ccb@mail.gmail.com>
Date: Sun, 7 Oct 2007 06:33:40 -0500
From: "Mark Steitle" <msteitle@gmail.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Hose clamp myth busters
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Al,
Thanks for the analysis.  I always wondered why cars, which use the "old
fashion" clamps, don't blow hoses left and right.  I guess I'm just a belt
and suspenders kind of guy.  I like the fact that they adjust to the
expansion.

Mark S.
(I used "Wiggins" couplings)


On 10/6/07, Al Gietzen <ALVentures@cox.net> wrote:
>
>   If those hose clamps are not constant torque clamps, please consider
> upgrading them before first flight.  They're available from McMaster.
>
>
>
> 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 so=
ld.
>  Certainly not picking on you, and I know our friend on the other list ma=
kes
> a big issue of the constant torque clamp.  IIRC, the main point raised wa=
s
> the effect of thermal expansion, more exactly the differential thermal
> expansion between the inner metal tube (aluminum in this case) and the cl=
amp
> (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 entire=
ly
> negligible. And besides, having that clamp just a wee smidgeon tighter wh=
en
> 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 =96 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 sugges=
t
> 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 =96 although contemporary automotive coolant hose c=
an be
> expected to last 6 =96 9 years.  The other thing, of course, is that on o=
ur
> 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
>

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<div>Al, </div>
<div>Thanks for the analysis.&nbsp; I always wondered why cars, which use t=
he &quot;old fashion&quot; clamps, don&#39;t blow hoses left and right.&nbs=
p; I guess I&#39;m just a belt and suspenders kind of guy.&nbsp; I like the=
 fact that they adjust to the expansion.&nbsp;=20
</div>
<div>&nbsp;</div>
<div>Mark S. </div>
<div>(I used &quot;Wiggins&quot; couplings)<br><br>&nbsp;</div>
<div><span class=3D"gmail_quote">On 10/6/07, <b class=3D"gmail_sendername">=
Al Gietzen</b> &lt;<a href=3D"mailto:ALVentures@cox.net">ALVentures@cox.net=
</a>&gt; wrote:</span>
<blockquote class=3D"gmail_quote" style=3D"PADDING-LEFT: 1ex; MARGIN: 0px 0=
px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">
<div lang=3D"EN-US" vlink=3D"blue" link=3D"blue">
<div>
<div>
<p style=3D"MARGIN-LEFT: 0.5in"><font face=3D"Times New Roman" size=3D"3"><=
span style=3D"FONT-SIZE: 12pt">If those hose clamps are not constant torque=
 clamps, please consider upgrading them before first flight.&nbsp; They&#39=
;re available from McMaster.&nbsp;=20
</span></font></p></div>
<div>
<p style=3D"MARGIN-LEFT: 0.5in"><font face=3D"Times New Roman" size=3D"3"><=
span style=3D"FONT-SIZE: 12pt">&nbsp;</span></font></p></div>
<p><font face=3D"Times New Roman" color=3D"blue" size=3D"3"><span style=3D"=
FONT-SIZE: 12pt; COLOR: blue">Mark;</span></font></p>
<p><font face=3D"Verdana" color=3D"blue" size=3D"2"><span style=3D"FONT-SIZ=
E: 11pt; COLOR: blue; FONT-FAMILY: Verdana">&nbsp;</span></font></p>
<p><font face=3D"Verdana" color=3D"blue" size=3D"2"><span style=3D"FONT-SIZ=
E: 11pt; COLOR: blue; FONT-FAMILY: Verdana">I have no objection to the use =
constant torque clamps, of course.&nbsp; But I will express my conclusion/o=
pinion that this clamp thing has been over sold. &nbsp;Certainly not pickin=
g on you, and I know our friend on the other list makes a big issue of the =
constant torque clamp.&nbsp; 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). &n=
bsp;Doing the math will show that this is less than infinitesimal.&nbsp; Th=
e temp change of the coolant may be about 80 C cold to hot.&nbsp; The clamp=
 heats up maybe 15C less than the aluminum. Assume a 1 =BD" diameter.&nbsp;=
 So the aluminum expands about=20
0.000037" on the diameter while the SS expands only 0.000012"; a huge diffe=
rence of 0.000025".&nbsp; 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 t=
hing.
</span></font></p>
<p><font face=3D"Verdana" color=3D"blue" size=3D"2"><span style=3D"FONT-SIZ=
E: 11pt; COLOR: blue; FONT-FAMILY: Verdana">&nbsp;</span></font></p>
<p><font face=3D"Verdana" color=3D"blue" size=3D"2"><span style=3D"FONT-SIZ=
E: 11pt; COLOR: blue; FONT-FAMILY: Verdana">Now, it is true that over time =
the elastomer loses some of its elasticity, mostly over the first few month=
s, and then very slowly over the next few years =96 depending on the type o=
f elastomer, of course.
</span></font></p>
<p><font face=3D"Verdana" color=3D"blue" size=3D"2"><span style=3D"FONT-SIZ=
E: 11pt; COLOR: blue; FONT-FAMILY: Verdana">&nbsp;</span></font></p>
<p><font face=3D"Verdana" color=3D"blue" size=3D"2"><span style=3D"FONT-SIZ=
E: 11pt; COLOR: blue; FONT-FAMILY: Verdana">So whether they are regular goo=
d quality clamps, properly tightened (not over-tightened), or constant torq=
ue clamps properly tightened; I'd suggest that the important factors are: r=
e-torque the clamps after a few weeks or a month of use; use the widest cla=
mp for the diameter, and consider high quality silicone hose =96 although c=
ontemporary automotive coolant hose can be expected to last 6 =96 9 years.&=
nbsp; The other thing, of course, is that on our planes we will probably ch=
ange out the hoses every second annual or so anyway.
</span></font></p>
<p><font face=3D"Verdana" color=3D"blue" size=3D"2"><span style=3D"FONT-SIZ=
E: 11pt; COLOR: blue; FONT-FAMILY: Verdana">&nbsp;</span></font></p>
<p><font face=3D"Verdana" color=3D"blue" size=3D"2"><span style=3D"FONT-SIZ=
E: 11pt; COLOR: blue; FONT-FAMILY: Verdana">One more thing.&nbsp; Consider =
putting a Schroeder valve on the system somewhere so you can easily pressur=
e test the system before you fly (or before you start your engine), and may=
be at annual time. &nbsp;It is so much easier to deal with any leak while t=
hings are cool and on the ground.
</span></font></p>
<p><font face=3D"Verdana" color=3D"blue" size=3D"2"><span style=3D"FONT-SIZ=
E: 11pt; COLOR: blue; FONT-FAMILY: Verdana">&nbsp;</span></font></p>
<p><font face=3D"Verdana" color=3D"blue" size=3D"2"><span style=3D"FONT-SIZ=
E: 11pt; COLOR: blue; FONT-FAMILY: Verdana">Sorry; did I go on too long</sp=
an></font><font face=3D"Wingdings" color=3D"blue" size=3D"2"><span style=3D=
"FONT-SIZE: 11pt; COLOR: blue; FONT-FAMILY: Wingdings">
J</span></font><font face=3D"Verdana" color=3D"blue" size=3D"2"><span style=
=3D"FONT-SIZE: 11pt; COLOR: blue; FONT-FAMILY: Verdana">?</span></font></p>
<p><font face=3D"Verdana" color=3D"blue" size=3D"2"><span style=3D"FONT-SIZ=
E: 11pt; COLOR: blue; FONT-FAMILY: Verdana">&nbsp;</span></font></p>
<p><font face=3D"Verdana" color=3D"blue" size=3D"2"><span style=3D"FONT-SIZ=
E: 11pt; COLOR: blue; FONT-FAMILY: Verdana">Al G</span></font></p></div></d=
iv></blockquote></div><br>

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