X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from nf-out-0910.google.com ([64.233.182.186] verified) by logan.com (CommuniGate Pro SMTP 5.1.12) with ESMTP id 2374427 for flyrotary@lancaironline.net; Sun, 07 Oct 2007 21:52:43 -0400 Received-SPF: pass receiver=logan.com; client-ip=64.233.182.186; envelope-from=rotary.thjakits@gmail.com Received: by nf-out-0910.google.com with SMTP id 30so802886nfu for ; Sun, 07 Oct 2007 18:52:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=beta; h=domainkey-signature:received:received:message-id:date:from:to:subject:in-reply-to:mime-version:content-type:references; bh=srsXhR8n1zfCEFRPDZKuBzO3QrSbNhSpssQQPCxVQm4=; b=A/dMT5QYiwjg4kYbjQ0PThDKQy0HI1sWtNzYwsg0MAmBCCUWL5yNkFZR5+gniCN2aN/9tOTpsNIstXlLINke14btcP5w/kkKLAsmAQ1z1tJpQj+9i9Qu67iDTdMUydXk7JYKMxRT/71V/RJvaGGnlIyjwy+R4AzY0RUGPqlACTw= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta; h=received:message-id:date:from:to:subject:in-reply-to:mime-version:content-type:references; b=goxNjndc20/ZxQWpY5vkfBaQpEXIJPDBL50LJbRXV2rkF+I+Y74soPlpBr7BghGGeMwTldev0F3OTVGysiztgYVQNZ+bMROkO+V+zfO8dzbCY6rLg+Ac4VKNzdYVd/T6eA77+DnKel8BgtusFyALLby/5tSCgtrbj2wb7ICsnYI= Received: by 10.78.170.6 with SMTP id s6mr48074hue.1191808325065; Sun, 07 Oct 2007 18:52:05 -0700 (PDT) Received: by 10.78.163.19 with HTTP; Sun, 7 Oct 2007 18:52:05 -0700 (PDT) Message-ID: <63163d560710071852u5376b41er349f6e4b581ef35d@mail.gmail.com> Date: Sun, 7 Oct 2007 20:52:05 -0500 From: "Thomas Jakits" To: "Rotary motors in aircraft" Subject: Re: [FlyRotary] Re: Hose clamp myth busters In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_34919_15569855.1191808325053" References: ------=_Part_34919_15569855.1191808325053 Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline 2nd Al's motion, I fly helicopters for a living (the certificated versions ....) The last one has some of the hydraulics system (low pressure to/from the cooler) and the turbine oil to cooler hoses clamped with 2 regular clamps o= n each end. Though the hoses are capped off with a metalcap that has to prong= s that go under the clamps, just to hold the cap on the hose end. Constant pressure is good, but good regular clamps will do fine. You can safety wire them too, allthough the ones on the helo are not. Then, I have to do a daily pre-flight inspection that includes to grap and pull the hoses somewhat. Short work of makeing sure the clamps are not loose, too. If you do not or cannot preflight the engine like that before every flight, safetywire will give you some peace of mind.. Wiggins is the "smoothest" custom touch though! Max points for coolness too= . Sometimes cool is nice, even if you need "people in the know" to appreciate details like "Wiggins" Cheers, TJ On 10/7/07, Mark Steitle wrote: > > 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 bel= t > 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 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 = 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 t= o > > 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 whil= e > > 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 enti= rely > > 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 =96 depending on the type of elastomer, of course. > > > > > > > > So whether they are regular good quality clamps, properly tightened (no= t > > over-tightened), or constant torque clamps properly tightened; I'd sugg= est > > 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= can be > > expected to last 6 =96 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 long J? > > > > > > > > Al G > > > > ------=_Part_34919_15569855.1191808325053 Content-Type: text/html; charset=WINDOWS-1252 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline
2nd Al's motion,
 
I fly helicopters for a living (the certificated versions ....)
The last one has some of the hydraulics system (low pressure to/from t= he cooler) and the turbine oil to cooler hoses clamped with 2 regular clamp= s on each end. Though the hoses are capped off with a metalcap that has to = prongs that go under the clamps, just to hold the cap on the hose end.
Constant pressure is good, but good regular clamps will do fine. You c= an safety wire them too, allthough the ones on the helo are not.
Then, I have to do a daily pre-flight inspection that includes to grap= and pull the hoses somewhat. Short work of makeing sure the clamps are not= loose, too.
 
If you do not or cannot preflight the engine like that before every fl= ight, safetywire will give you some peace of mind..
 
Wiggins is the "smoothest" custom touch though! Max points f= or coolness too.
 
Sometimes cool is nice, even if you need "people in the know"= ; to appreciate details like "Wiggins"
 
Cheers,
 
TJ

 
On 10/7/07, = Mark Steitle <msteitle@gmail.c= om> wrote:
Al,
Thanks for the analysis.  I always wondered why cars, which use t= he "old fashion" clamps, don't blow hoses left and right.&nbs= p; I guess I'm just a belt and suspenders kind of guy.  I like the= fact that they adjust to the expansion. =20
 
Mark S.
(I used "Wiggins" couplings)

 
On 10/6/07, = Al Gietzen <ALVentures@cox.net= > wrote: =20

<= span style=3D"FONT-SIZE: 12pt">If those hose clamps are not constant torque= clamps, please consider upgrading them before first flight.  They'= ;re available from McMaster. =20

<= span style=3D"FONT-SIZE: 12pt"> 

Mark;

 

I have no objection to the use = constant torque clamps, of course.  But I will express my conclusion/o= pinion that this clamp thing has been over sold.  Certainly not pickin= g 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). &n= bsp;Doing the math will show that this is less than infinitesimal.  Th= e 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.&= nbsp; So the aluminum expands about=20 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 t= he thickness of the elastomer hose is entirely negligible. And besides, hav= ing that clamp just a wee smidgeon tighter when it is hot and pressurized c= an't be a bad thing.=20

 

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.=20

 

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 ar= e: 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 althou= gh contemporary automotive coolant hose can be expected to last 6 =96 9 yea= rs.  The other thing, of course, is that on our planes we will probabl= y change out the hoses every second annual or so anyway.=20

 

One more thing.  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.  It is so much easier to deal with any leak while t= hings are cool and on the ground.=20

 

Sorry; did I go on too long J?

 

Al G



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