---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Tue 03/05/19: 1 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:35 AM - Re: Insulator in durable gas tight compression (Robert L. Nuckolls, III) ________________________________ Message 1 _____________________________________ Time: 06:35:37 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Insulator in durable gas tight compression At 11:48 AM 3/4/2019, you wrote: >Tasker > >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.=C2 Ceramic would >work, but that is hared to work with.=C2 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 . . . ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message aeroelectric-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/AeroElectric-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/aeroelectric-list Browse Digests http://www.matronics.com/digest/aeroelectric-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.