X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from imo-d05.mx.aol.com ([205.188.157.37] verified) by logan.com (CommuniGate Pro SMTP 5.1.12) with ESMTP id 2377516 for flyrotary@lancaironline.net; Tue, 09 Oct 2007 11:28:55 -0400 Received-SPF: pass receiver=logan.com; client-ip=205.188.157.37; envelope-from=WRJJRS@aol.com Received: from WRJJRS@aol.com by imo-d05.mx.aol.com (mail_out_v38_r9.3.) id q.bff.22fb0a44 (60465) for ; Tue, 9 Oct 2007 11:27:53 -0400 (EDT) Received: from FWM-M13 (fwm-m13.webmail.aol.com [64.12.168.77]) by ciaaol-m01.mx.aol.com (v119.11) with ESMTP id MAILCIAAOLM012-ec31470b9df82fa; Tue, 09 Oct 2007 11:27:52 -0400 References: To: flyrotary@lancaironline.net Subject: Re: [FlyRotary] Re: Hose clamp myth busters Date: Tue, 09 Oct 2007 11:27:52 -0400 In-Reply-To: X-MB-Message-Source: WebUI MIME-Version: 1.0 From: wrjjrs@aol.com X-MB-Message-Type: User Content-Type: multipart/alternative; boundary="--------MB_8C9D8A017ADB7AC_F30_B139_FWM-M13.sysops.aol.com" X-Mailer: AOL WebMail 31361-STANDARD Received: from 65.161.241.3 by FWM-M13.sysops.aol.com (64.12.168.77) with HTTP (WebMailUI); Tue, 09 Oct 2007 11:27:52 -0400 Message-Id: <8C9D8A017ADB7AC-F30-5827@FWM-M13.sysops.aol.com> X-AOL-IP: 64.12.168.77 X-Spam-Flag: NO ----------MB_8C9D8A017ADB7AC_F30_B139_FWM-M13.sysops.aol.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Tracy, These are a modern and viable clamp system. I would be concerned abou= t the maximum allowable in service temperature is for rotary use. A standard= worm type clamp is safe and reasonably light. (lighter than AN and stainles= s braided at least) The other thing I would be concerned about is the tempta= tion to use a marginal size fit (operator error to be sure) on=C2=A0the next= size smaller tube.=C2=A0Used properly they do work great. Bill Jepson=C2=A0 -----Original Message----- From: Tracy Crook To: Rotary motors in aircraft Sent: Tue, 9 Oct 2007 7:37 am Subject: [FlyRotary] Re: Hose clamp myth busters Am I the only fan of Gates 'Power Grip' hose clamps?=C2=A0 They are heat shr= inkable sleeves made for this application. =C2=A0 They have everything I like in a hose clamp except one=C2=A0 (they are not r= eusable) (OK, maybe two, every hose size needs a different clamp part number= and size) =C2=A0 They are the=C2=A0=C2=A0lightest, have constant grip force, most evenly dist= ributed clamping force of all types, widest grip area, low in cost (if const= ant hose removal not required)=C2=A0 and can be used in tight places where t= here is no way to get a tool on them to tighten (I have a few of those).=C2= =A0=C2=A0They NEVER loosen and require no checking or safety wiring.=C2=A0 I= know of no failures of these clamps.=C2=A0=C2=A0=C2=A0 These properties mak= e them the clamp of choice for me.=C2=A0=20 =C2=A0 =C2=A0Only place I don't use them is on oil lines but of course I use no cla= mps at all there (Aeroquip push on connectors and hose) =C2=A0 On an airplane, I have as much use for those heavy spring loaded constant fo= rce hose clamps as I do a bumper jack.=C2=A0 If I was a semi truck=C2=A0driv= er, they are the only thing I'd use. =C2=A0 Tracy=C2=A0 (starving - Laura on 8 day trip to Hawaii) =C2=A0 On 10/7/07, Thomas Jakits wrote:=20 2nd Al's motion, =C2=A0 I fly helicopters for a living (the certificated versions ....) The last one has some of the hydraulics system (low pressure to/from the coo= ler) and the turbine oil to cooler hoses clamped with 2 regular clamps on ea= ch end. Though the hoses are capped off with a metalcap that has to prongs t= hat 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 can saf= ety wire them too, allthough the ones on the helo are not.=20 Then, I have to do a daily pre-flight inspection that includes to grap and p= ull the hoses somewhat. Short work of makeing sure the clamps are not loose,= too. =C2=A0 If you do not or cannot preflight the engine like that before every flight,=20= safetywire will give you some peace of mind.. =C2=A0 Wiggins is the "smoothest" custom touch though! Max points for coolness too. =C2=A0 Sometimes cool is nice, even if you need "people in the know" to appreciate=20= details like "Wiggins" =C2=A0 Cheers, =C2=A0 TJ =C2=A0 On 10/7/07, Mark Steitle wrote:=20 Al,=20 Thanks for the analysis.=C2=A0 I always wondered why cars, which use the "ol= d fashion" clamps, don't blow hoses left and right.=C2=A0 I guess I'm just a= belt and suspenders kind of guy.=C2=A0 I like the fact that they adjust to=20= the expansion.=C2=A0=20 =C2=A0 Mark S.=20 (I used "Wiggins" couplings) =C2=A0 On 10/6/07, Al Gietzen wrote:=20 If those hose clamps are not constant torque clamps, please consider upgradi= ng them before first flight.=C2=A0 They're available from McMaster.=C2=A0=20 =C2=A0 Mark; =C2=A0 I have no objection to the use constant torque clamps, of course.=C2=A0 But=20= I will express my conclusion/opinion that this clamp thing has been over sol= d. =C2=A0Certainly not picking on you, and I know our friend on the other li= st makes a big issue of the constant torque clamp.=C2=A0 IIRC, the main poin= t raised was the effect of thermal expansion, more exactly the differential=20= thermal expansion between the inner metal tube (aluminum in this case) and t= he clamp (usually SS). =C2=A0Doing the math will show that this is less than= infinitesimal.=C2=A0 The temp change of the coolant may be about 80 C cold=20= to hot.=C2=A0 The clamp heats up maybe 15C less than the aluminum. Assume a=20= 1 =C2=BD" diameter.=C2=A0 So the aluminum expands about 0.000037" on the dia= meter while the SS expands only 0.000012"; a huge difference of 0.000025".= =C2=A0 I am certain that this effect on the thickness of the elastomer hose=20= is entirely negligible. And besides, having that clamp just a wee smidgeon t= ighter when it is hot and pressurized can't be a bad thing.=20 =C2=A0 Now, it is true that over time the elastomer loses some of its elasticity, m= ostly over the first few months, and then very slowly over the next few year= s =E2=80=93 depending on the type of elastomer, of course.=20 =C2=A0 So whether they are regular good quality clamps, properly tightened (not ove= r-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 mont= h of use; use the widest clamp for the diameter, and consider high quality s= ilicone hose =E2=80=93 although contemporary automotive coolant hose can be=20= expected to last 6 =E2=80=93 9 years.=C2=A0 The other thing, of course, is t= hat on our planes we will probably change out the hoses every second annual=20= or so anyway.=20 =C2=A0 One more thing.=C2=A0 Consider putting a Schroeder valve on the system somew= here so you can easily pressure test the system before you fly (or before yo= u start your engine), and maybe at annual time. =C2=A0It is so much easier t= o deal with any leak while things are cool and on the ground.=20 =C2=A0 Sorry; did I go on too long J? =C2=A0 Al G ________________________________________________________________________ Email and AIM finally together. You've gotta check out free AOL Mail! - http= ://mail.aol.com ----------MB_8C9D8A017ADB7AC_F30_B139_FWM-M13.sysops.aol.com Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset="utf-8" Tracy, These are a modern and viable clamp system. I would be concerned= about the maximum allowable in service temperature is for rotary use. A sta= ndard worm type clamp is safe and reasonably light. (lighter than AN and sta= inless braided at least) The other thing I would be concerned about is the t= emptation to use a marginal size fit (operator error to be sure) on the= next size smaller tube. Used properly they do work great.
Bill Jepson 


-----Original Message-----
From: Tracy Crook <tracy@rotaryaviation.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Tue, 9 Oct 2007 7:37 am
Subject: [FlyRotary] Re: Hose clamp myth busters

Am I the only fan of Gates 'Power Grip' hose clamps?  They are hea= t shrinkable sleeves made for this application.
 
They have everything I like in a hose clamp except one  (they are=20= not reusable) (OK, maybe two, every hose size needs a different clamp part n= umber 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=20= constant hose removal not required)  and can be used in tight places wh= ere there is no way to get a tool on them to tighten (I have a few of those)= .  They NEVER loosen and require no checking or safety wiring.&nbs= p; 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 n= o clamps at all there (Aeroquip push on connectors and hose)
 
On an airplane, I have as much use for those heavy spring loaded consta= nt force hose clamps as I do a bumper jack.  If I was a semi truck = ;driver, they are the only thing I'd use.
 
Tracy  (starving - Laura on 8 day trip to Hawaii)


 
On 10/7/07, Thoma= s Jakits <rotary.thjakit= s@gmail.com> wrote:=20
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 th= e cooler) and the turbine oil to cooler hoses clamped with 2 regular clamps=20= 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 ca= n 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=20= and pull the hoses somewhat. Short work of makeing sure the clamps are not l= oose, too.
 
If you do not or cannot preflight the engine like that before every fli= ght, 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 apprec= iate details like "Wiggins"
 
Cheers,
 
TJ

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

 
On 10/6/07, Al Gi= etzen <ALVentures@cox.net&g= t; wrote:
If those hose clamps are not constant torque c= lamps, please consider upgrading them before first flight.  They're ava= ilable from McMaster. 
 
Mark;
 
I have no objection to the use consta= nt torque clamps, of course.  But I will express my conclusion/opinion=20= 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=20= torque clamp.  IIRC, the main point raised was the effect of thermal ex= pansion, more exactly the differential thermal expansion between the inner m= etal tube (aluminum in this case) and the clamp (usually SS).  Doing th= e 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 mayb= e 15C less than the aluminum. Assume a 1 =C2=BD" diameter.  So the alum= inum expands about 0.000037" on the diameter while the SS expands only 0.000= 012"; a huge difference of 0.000025".  I am certain that this effect on= the thickness of the elastomer hose is entirely negligible. And besides, ha= ving that clamp just a wee smidgeon tighter when it is hot and pressurized c= an't be a bad thing.
 
Now, it is true that over time the el= astomer loses some of its elasticity, mostly over the first few months, and=20= then very slowly over the next few years =E2=80=93 depending on the type of=20= elastomer, of course.
 
So whether they are regular good qual= ity clamps, properly tightened (not over-tightened), or constant torque clam= ps 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 th= e diameter, and consider high quality silicone hose =E2=80=93 although conte= mporary automotive coolant hose can be expected to last 6 =E2=80=93 9 years.=   The other thing, of course, is that on our planes we will probably ch= ange out the hoses every second annual or so anyway.
 
One more thing.  Consider puttin= g a Schroeder valve on the system somewhere so you can easily pressure test=20= the system before you fly (or before you start your engine), and maybe at an= nual 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



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