X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from nz-out-0506.google.com ([64.233.162.226] verified) by logan.com (CommuniGate Pro SMTP 5.1.12) with ESMTP id 2377350 for flyrotary@lancaironline.net; Tue, 09 Oct 2007 10:38:39 -0400 Received-SPF: pass receiver=logan.com; client-ip=64.233.162.226; envelope-from=rwstracy@gmail.com Received: by nz-out-0506.google.com with SMTP id n29so865841nzf for ; Tue, 09 Oct 2007 07:38:00 -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:sender:to:subject:in-reply-to:mime-version:content-type:references:x-google-sender-auth; bh=L9N1qjXrpSzyELbkHyKyEKqaazMNQAM92p1xrEUTQNE=; b=uLXvBVHByfJrKiv1/xQ7XHEtBd85aJWogR7ntalbbaDpL7WB8a6zjo1vsW15a/OF+vEui/ax7iVoQBTdJyDK2+GvLedSi6qDncXz8nZC5nSWbbWYldZf4jOZpP7lrJx24J0fz4RPM7rwLoSyWF0ZWDmPZrF/3vIQjaKnPWI6UwY= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta; h=received:message-id:date:from:sender:to:subject:in-reply-to:mime-version:content-type:references:x-google-sender-auth; b=s3gB4CPY0LO3B4rqt/r4MQrUn0i+I6dmYo5btPDEe6S3z0CuoNASaSlcz4U2WmOdWJ4qXf23XavjCt29VJCvQAw1pNNn9arFC/8BwFlB4f7OdPn1+Na11zHfczfd0Non7sveJdw5IZyJKM/QBaXNYnkblT+fXIq2OACEkPLZWNU= Received: by 10.142.12.14 with SMTP id 14mr2468384wfl.1191940679460; Tue, 09 Oct 2007 07:37:59 -0700 (PDT) Received: by 10.143.28.1 with HTTP; Tue, 9 Oct 2007 07:37:59 -0700 (PDT) Message-ID: <1b4b137c0710090737w3ef10c12n8a65b1d2b8a55446@mail.gmail.com> Date: Tue, 9 Oct 2007 10:37:59 -0400 From: "Tracy Crook" Sender: rwstracy@gmail.com 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_4989_10537009.1191940679418" References: X-Google-Sender-Auth: c16129d855954f07 ------=_Part_4989_10537009.1191940679418 Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline Am I the only fan of Gates 'Power Grip' hose clamps? They are heat shrinkable sleeves made for this application. They have everything I like in a hose clamp except one (they are not reusable) (OK, maybe two, every hose size needs a different clamp part number and size) They are the lightest, have constant grip force, most evenly distributed clamping force of all types, widest grip area, low in cost (if constant hos= e removal not required) and can be used in tight places where there is no wa= y to get a tool on them to tighten (I have a few of those). They NEVER loose= n and require no checking or safety wiring. I know of no failures of these clamps. These properties make them the clamp of choice for me. Only place I don't use them is on oil lines but of course I use no clamps at all there (Aeroquip push on connectors and hose) On an airplane, I have as much use for those heavy spring loaded constant force hose clamps as I do a bumper jack. If I was a semi truck driver, the= y are the only thing I'd use. Tracy (starving - Laura on 8 day trip to Hawaii) On 10/7/07, Thomas Jakits wrote: > > 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= on > each end. Though the hoses are capped off with a metalcap that has to pro= ngs > 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 an= d > 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 "ol= d > > fashion" clamps, don't blow hoses left and right. I guess I'm just a b= elt > > 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 conside= r > > > upgrading them before first flight. They're available from McMaster. > > > > > > > > > > > > Mark; > > > > > > > > > > > > I have no objection to the use constant torque clamps, of course. Bu= t > > > I will express my conclusion/opinion that this clamp thing has been o= ver > > > sold. Certainly not picking on you, and I know our friend on the oth= er 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 th= ermal > > > expansion between the inner metal tube (aluminum in this case) and th= e 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 smidge= on > > > 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 ov= er 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 > > > 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 c= onsider > > > high quality silicone hose =96 although contemporary automotive coola= nt hose > > > can be expected to last 6 =96 9 years. The other thing, of course, i= s 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 mu= ch > > > 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_4989_10537009.1191940679418 Content-Type: text/html; charset=WINDOWS-1252 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline
Am I the only fan of Gates 'Power Grip' hose clamps?  The= y are heat shrinkable sleeves made for this application.
 
They have everything I like in a hose clamp except one  (they are= not reusable) (OK, maybe two, every hose size needs a different clamp part= number and size)
 
They are the  lightest, have constant grip force, most evenl= y distributed clamping force of all types, widest grip area, low in cost (i= f constant hose removal not required)  and can be used in tight places= where there is no way to get a tool on them to tighten (I have a few of th= ose).  They NEVER loosen and require no checking or safety wiring= .  I know of no failures of these clamps.    These prop= erties make them the clamp of choice for me. 
 
 Only place I don't use them is on oil lines but of course I = use no clamps at all there (Aeroquip push on connectors and hose)
 
On an airplane, I have as much use for those heavy spring loaded const= ant force hose clamps as I do a bumper jack.  If I was a semi truck&nb= sp;driver, they are the only thing I'd use.
 
Tracy  (starving - Laura on 8 day trip to Hawaii)


 
On 10/7/07, = Thomas Jakits <rotary.t= hjakits@gmail.com> wrote:
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.=20
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:=20
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



=

------=_Part_4989_10537009.1191940679418--