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Date:         Wed, 10 Jun 2009 13:44:48 -0400
Reply-To:     VW Doka <vw.doka@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         VW Doka <vw.doka@GMAIL.COM>
Subject:      Re: Correct use of Dielectric grease?
Comments: To: Jonathan Farrugia <jfarrugi@umich.edu>
In-Reply-To:  <Pine.LNX.4.64.0906101256450.17312@goldenaxe.gpcc.itd.umich.edu>
Content-Type: text/plain; charset=ISO-8859-1

Good explantion.... but "springyness"?

IIRC, quite a few Japanese cars came with gobs of grease (a brown/orange color) in the light sockets for the tail lights and turn signals. I've seen this on a few other mfgs. as well.

It's a nice add-on for those pesky, love to rust, front turn signal sockets on the Vanagons.

Cheers,

Jeff

On Wed, Jun 10, 2009 at 1:22 PM, Jonathan Farrugia<jfarrugi@umich.edu> wrote: > dielectric grease is used in layman's terms to prevent dielectric > corrosion.  that is corrosion between two dissimilar metals that have > different voltages of reduction (that is a physic/chemistry term).  when > dissimilar metals have different reduction voltages one can oxidize the > other, oxidation is what is commonly referred to as corrosion.  in > addition to oxidation by other metals oxidation can occur from other > atomic elements such as chlorine as is the case with salt compounds. > > if oxygen is excluded from the metals by the use of a coating whether that > be paint or grease no oxidation can occur.  that is why dielectric grease > is used. > > okay onto the part of the question that asked about electrical connections > being hindered by the grease.  all electrical connections rely on physical > contact ie pressure to work.  the 'best' electrical connection in simple > terms could be thought of as a bolted connection.  that connection type > gives very high pressures, most hight voltage stuff is of the bolted > connection type.  a bolted connection is not always practical in economic > or physical terms.  another method of electrical connection is a spring > type connection. > > if you have ever been in a circuit breaker box that doesn't use screw and > the breakers just pop in it is because a spring finger type connection > system is being used.  push type connectors used in the vanagon system are > of the same spring design.  lets take the case of a normal 1/4" male and > female blade connector.  the male part is of a fixed dimension.  the > female part is constructed from a spring type material.  when you push the > two together the female part made of spring material expands over the male > blade.  the connection here is made metal to metal with the pressure > provided by the spring.  the spring is the sole clamping force for this > connection.  if you have adequate force by design at your connection it > will be strong enough to displace any grease and the metal to metal > connection will be made. > > spring connectors are subject to problems when exposed to high heat.  this > is why it is bad to reuse connections that have been overheated > electrically.  the heating changes the springyness of the connector and > thus the clamping force of the connection is reduced.  this often can lead > to a poor/loose connection and arcing at the connection site. > > those are my thoughts for what they are worth please take them as a > starting point for your further research. > > jonathan >


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