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spade lug failure.

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sarg314(at)comcast.net
Guest

Posted: Fri Aug 31, 2007 4:48 pm Post subject: spade lug failure.

I have been wiring my plane using some high quality (well, at least 

they're expensive - $0.65 each) T&B insulated fast-on type connectors 

and an Ideal crimping tool (not expensive as crimpers go - about $50).  

A couple days ago I found a #22 ground wire that simply didn't conduct.  

I removed it from the plane and sliced away insulation near each end to 

expose the wire just before the connectors  and determined which one 

wasn't conducting.  It looked fine.  The wires were just visible 

sticking out of the spade lug end and I could touch them directly with 

my continuity tester, but they weren't connected to the rest of the wire. 



Using a dremel tool, I removed the plastic covering and part of the 

crimp.  A little bit of the insulation extended into the part of the 

barrel that crimps the copper wire.  Apparently what happened was that 

the act of crimping it cut thru the wire, but NOT thru the insulation.  

The connector was held on by the insulation. That tefzel is pretty tough 

stuff.



I made a new wire and got things working, but I have to wonder if more 

of my wires aren't in the same or nearly the same condition.  Am I doing 

something wrong here or was this probably just a  1 in a 1000 fluke?  Do 

I need to check the connections that seem to be working?  If so, how?

--

Tom Sargent, RV-6A

Electrical system

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sarg314(at)comcast.net
Guest

Posted: Sun Sep 09, 2007 2:09 pm Post subject: spade lug failure.

I didn't get any responses to this, but I found an explanation for it 

that I thought I should post.  After carefully examining the bad female 

lug, I noticed that it was of a different design than all the others.  

It had had the same plastic insulating shrowd on it, but the metal 

connector itself was different.  I could not find one like it in all my 

parts bins.   I was also unable to duplicate the problem by crimping a 

dozen test connectors trying to make every mistake I could think of.



So, I'm concluding that it was one of a different design that the 

manufacturer or seller (Allied Electronics) got into the wrong parts bag 

by mistake.  It is probably designed for a different crimping tool and 

the one I have crimped it differently and caused bad results.  I have 

yet to check all the connectors in the plane to verify that there were 

no others like it that got installed.  But I think my crimper is OK and 

my connectors are OK too.  Testing of the electrical system is going well.



sarg314 wrote:



 	  Quote: 	
		   



 Using a dremel tool, I removed the plastic covering and part of the 

 crimp.  A little bit of the insulation extended into the part of the 

 barrel that crimps the copper wire.  Apparently what happened was that 

 the act of crimping it cut thru the wire, but NOT thru the 

 insulation.  The connector was held on by the insulation. That tefzel 

 is pretty tough stuff.

 -- 

 Tom Sargent, RV-6A


	


--

Tom Sargent, RV-6A, electrical system

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nuckolls.bob(at)cox.net
Guest

Posted: Mon Sep 10, 2007 6:44 am Post subject: spade lug failure.

At 05:44 PM 8/31/2007 -0700, you wrote:



 	  Quote: 	
		  



I have been wiring my plane using some high quality (well, at least 

they're expensive - $0.65 each) T&B insulated fast-on type connectors and 

an Ideal crimping tool (not expensive as crimpers go - about $50).

A couple days ago I found a #22 ground wire that simply didn't conduct.

I removed it from the plane and sliced away insulation near each end to 

expose the wire just before the connectors  and determined which one 

wasn't conducting.  It looked fine.  The wires were just visible sticking 

out of the spade lug end and I could touch them directly with my 

continuity tester, but they weren't connected to the rest of the wire.

Using a dremel tool, I removed the plastic covering and part of the 

crimp.  A little bit of the insulation extended into the part of the 

barrel that crimps the copper wire.  Apparently what happened was that the 

act of crimping it cut thru the wire, but NOT thru the insulation.

The connector was held on by the insulation. That tefzel is pretty tough 

stuff.



I made a new wire and got things working, but I have to wonder if more of 

my wires aren't in the same or nearly the same condition.  Am I doing 

something wrong here or was this probably just a  1 in a 1000 fluke?  Do I 

need to check the connections that seem to be working?  If so, how?


	


     Good question. What you're experiencing is a demonstration

     of the fact that there is a menage a trois to be

     crafted between wires, terminals and tools that apply them.

     Some time ago I crafted some articles on terminal and tool

     performance. I'll suggest you review:



http://www.aeroelectric.com/articles/terminal.pdf



http://www.aeroelectric.com/articles/CrimpTools/crimptools.html



http://www.aeroelectric.com/articles/rules/review.html



    Your reported experience does raise some questions. I'd

    do a pull-test on a terminal crimped to a wire. When

    it fails, there should be a clean break between the loose

    strands and where the closed barrel turns them into

    a solid mass. You should not pull any strands out of

    the crimp.



    I did some tests on AMP tools putting AMP terminals

    on 22AWG Tefzel a few years ago and found that you could

    put a terminal on an UNSTRIPPED wire. When you think

    about the pressure (tens of thousands of PSI) it takes

    to bring the copper barrel into intimate contact with

    the copper strands, there's no way some layer of plastic

    is going to figure in a discontinuity. The plastic

    extrudes out of the joint like toothpaste.



    Having offered all this, I'll have to confess that

    what you've stated does give rise to some concerns.

    If one terminal was found to be insufficiently installed

    by ACCIDENT, what might you find if other terminals

    were investigated deliberately. I wish I could give

    you some warm fuzzies about this . . .



    Bob . . .

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