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Insulator in durable gas tight compression

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nuckolls.bob(at)aeroelect
Guest

Posted: Mon Mar 04, 2019 7:24 am Post subject: Insulator in durable gas tight compression

At 02:28 AM 3/4/2019, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: Jan de Jong <jan_de_jong(at)casema.nl>

 Is there any example in acceptable practices where

 an insulating layer (some laminate?) is part of the

 stack of metal layers that is compressed to ensure

 a durable gas tight low resistance electrical

 connection between the metal layers? 	


   Not aware of a joining technology

   that uses any form of insulation to

   augment integrity of the finished

   joint. Gas-tight implies metal-to-

   metal free of voids. Insulation

   or any other material outside the

   joint might be useful for protecting

   the edges of the joint . . . like

   solder over the 'western union'

   splice or heat-shrink over

   any other form of joining.



   There are dozens of insulation-

   displacement technologies wherein the

   conductors push the insulation aside

   during application . . . but it's

   not clear that insulation surrounding

   the finished joint is an integral

   component of the design's service

   life. 



 



 



 

   Bob . . .

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nuckolls.bob(at)aeroelect
Guest

Posted: Tue Mar 05, 2019 6:35 am Post subject: Insulator in durable gas tight compression

At 11:48 AM 3/4/2019, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: Dick Tasker <dick(at)thetaskerfamily.com>



 I believe you are asking is it okay to use some sort of laminate in the stack-up of layers wherein the goal is to have something to mount the connection to and insulate it from your airplane sheet metal and that will not affect the "gas-tightness" of the connection.



 If that is the question, I believe that the answer would be that there are very few materials that would allow that.Â  Ceramic would work, but that is hared to work with.Â  Any plastic type material probably is too soft to not allow some relaxation over time of the joint. 	


   Great catch Dick . . . I had a totally

   different image for his question!



   Yes, the way to achieve the ultimate

   gas-tight connection between two

   conductors is to mash them together

   with enough force that the two metals

   deform to conform with each other.



   Obviously, limits to force that can be

   applied are influenced by the relative

   hardness of materials involved in the

   force column. Too hard won't mash; too soft

   (like an intermediate layer of non-conductor)

   and the important materials (conductors) don't

   mash and retain their intimate contact over

   time.



   One or more OBAM aircraft feature composite

   firewall structures. To install a high

   integrity firewall ground . . .



  https://tinyurl.com/y4x3k24g



 

   . . . we included a stack of washers(4)

   from which the installer might craft a

   HARD spacer between the forward and

   aft bus bars. This feature prevented

   crushing the firewall composite matrix

   such that gas-tight integrity of the

   electrical connections was compromised.



   Having said that, one might appropriately

   question the design of Carling switches

   (and others) that place insulating

   materials in the force-column that joins

   electrical conductors of their products.



  https://tinyurl.com/8cm52v



   This is one (of no doubt many) instances

   where the designers have selected their

   non-conducting housing materials carefully

   to minimize effects on manufactured

   joints in the conductor pathways.



   Ideal? Perhaps not. Failure proof? We

   seen some failures . . . precipitated

   by heating events OUTSIDE the force

   column that degraded the plastic

   and destroyed integrity of the

   otherwise dependable joints.

   Hundreds of thousands of these

   switches have met design goals in

   tens of thousands of TC aircraft

   for decades.



   So the short answer is, yeah you can

   do it . . . others have done it . . .

   but with well considered properties

   of materials.



  



 

   Bob . . .

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