X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [66.219.56.248] (HELO qnsi-xch.qnsi.net) by logan.com (CommuniGate Pro SMTP 5.1.12) with ESMTP id 2390504 for flyrotary@lancaironline.net; Tue, 16 Oct 2007 17:55:53 -0400 Received-SPF: none receiver=logan.com; client-ip=66.219.56.248; envelope-from=bhughes@qnsi.net Content-class: urn:content-classes:message Return-Receipt-To: "Bobby J. Hughes" MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----_=_NextPart_001_01C81048.1903F0BC" Disposition-Notification-To: "Bobby J. Hughes" X-MimeOLE: Produced By Microsoft Exchange V6.5.6944.0 Subject: RE: [FlyRotary] Re: Hose clamp myth busters Date: Tue, 16 Oct 2007 16:58:46 -0600 Message-ID: X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: [FlyRotary] Re: Hose clamp myth busters Thread-Index: AcgKivFK6xj6Gx5rQKCP9Cs8mLnWjQFvOIzA From: "Bobby J. Hughes" To: "Rotary motors in aircraft" This is a multi-part message in MIME format. ------_=_NextPart_001_01C81048.1903F0BC Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Tracy, =20 Will the Power Grip clamps work with barbed fittings or just the smooth = bead fittings? =20 Bobby (ordering more stuff) ________________________________ From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On = Behalf Of Tracy Crook Sent: Tuesday, October 09, 2007 8:38 AM To: Rotary motors in aircraft Subject: [FlyRotary] Re: Hose clamp myth busters Am I the only fan of Gates 'Power Grip' hose clamps? They are heat = shrinkable sleeves made for this application. =20 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) =20 They are the lightest, have constant grip force, most evenly = distributed clamping force of all types, widest grip area, low in cost = (if 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 = those). They NEVER loosen 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. =20 =20 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) =20 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, they are the only thing I'd use. =20 Tracy (starving - Laura on 8 day trip to Hawaii) =20 On 10/7/07, Thomas Jakits wrote:=20 2nd Al's motion, =20 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 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 = can safety 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 pull the hoses somewhat. Short work of makeing sure the clamps are = not loose, too. =20 If you do not or cannot preflight the engine like that before every = flight, safetywire will give you some peace of mind.. =20 Wiggins is the "smoothest" custom touch though! Max points for coolness = too. =20 Sometimes cool is nice, even if you need "people in the know" to = appreciate details like "Wiggins" =20 Cheers, =20 TJ =09 =20 On 10/7/07, Mark Steitle wrote:=20 Al,=20 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. =20 =20 Mark S.=20 (I used "Wiggins" couplings) =09 =20 =09 On 10/6/07, Al Gietzen wrote:=20 If those hose clamps are not constant torque clamps, please consider = upgrading them before first flight. They're available from McMaster. =20 =20 Mark; =20 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.=20 =20 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.=20 =20 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.=20 =20 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.=20 =20 Sorry; did I go on too long :-)? =20 Al G ------_=_NextPart_001_01C81048.1903F0BC Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Tracy,
 
Will the Power Grip clamps work with barbed = fittings or=20 just the smooth bead fittings?
 
Bobby
(ordering more stuff)

From: Rotary motors in aircraft=20 [mailto:flyrotary@lancaironline.net] On Behalf Of Tracy=20 Crook
Sent: Tuesday, October 09, 2007 8:38 AM
To: = Rotary=20 motors in aircraft
Subject: [FlyRotary] Re: Hose clamp myth=20 busters

Am I the only fan of Gates 'Power Grip' hose clamps?  They are = heat=20 shrinkable sleeves made for this application.
 
They have everything I like in a hose clamp except one  (they = are not=20 reusable) (OK, maybe two, every hose size needs a different clamp part = number=20 and size)
 
They are the  lightest, have constant grip force, most = evenly=20 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 where=20 there is no way to get a tool on them to tighten (I have a few of=20 those).  They NEVER loosen and require no checking or safety=20 wiring.  I know of no failures of these clamps.    = These=20 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=20 clamps at all there (Aeroquip push on connectors and hose)
 
On an airplane, I have as much use for those heavy spring loaded = constant=20 force hose clamps as I do a bumper jack.  If I was a semi=20 truck driver, they are the only thing I'd use.
 
Tracy  (starving - Laura on 8 day trip to Hawaii)


 
On 10/7/07, Thomas=20 Jakits <rotary.thjakits@gmail.com&g= t;=20 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 the=20 cooler) and the turbine oil to cooler hoses clamped with 2 regular = clamps on=20 each end. Though the hoses are capped off with a metalcap that has to = prongs=20 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=20 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=20 loose, too.
 
If you do not or cannot preflight the engine like that before = every=20 flight, safetywire will give you some peace of mind..
 
Wiggins is the "smoothest" custom touch though! Max points for = coolness=20 too.
 
Sometimes cool is nice, even if you need "people in the know" to=20 appreciate details like "Wiggins"
 
Cheers,
 
TJ

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

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

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

 

Mark;

 

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

 

So = whether they=20 are regular good quality clamps, properly tightened (not = over-tightened),=20 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=20 of use; use the widest clamp for the diameter, and consider high = quality=20 silicone hose =96 although contemporary automotive coolant hose = can be=20 expected to last 6 =96 9 years.  The other thing, of course, = is that on=20 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=20 you can easily pressure test the system before you fly (or before = you=20 start your engine), and maybe at annual time.  It is so much = easier=20 to deal with any leak while things are cool and on the ground.=20

 

Sorry; did I go=20 on too long=20 J?

 

Al=20 = G




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