Re: Alternatives to those pre insulated *** joints

Dave Plowman (News) wrote:

In article <5kJUi.880$FQ2.322@xxxxxxxxxxxxxxxxxxxx>,
Chris Whelan <cawhelan@xxxxxxxxxxxx> wrote:
I've probably looked inside more crimped connections in order to
check that they had been made properly than the total number of
connections of all types that you have ever made in your life.

Your reply suggests not. A properly crimped terminal is shaped round
the conductor. I've got many crimp tools for various uses and they
generally all work the same - they have heart shaped jaws which are
designed to pinch the originally round terminal back on itself pulling
in the sides etc. A pre-insulated type simply flattens the lot.

Dave, this reply suggests that you do not know how a properly crimped
connection is formed. Google for "cold-welded crimp".

I don't need to.

You do if you want to understand why a statement like "A properly crimped
terminal is shaped round the conductor" is absolute rubbish.

BTW - you have no idea how many I've made or examined.

No, I don't. You did say earlier that your use of them was confined to
an amateur basis however. Mine is most definitely not.

On an amateur basis as far as cars are concerned. Like you.

Indeed. However, as I stated earlier, the environment I was working in was
very similar to that fond in a car WRT vibration, termination strain and
contamination.

As I said elsewhere in this thread, I worked in the electrical
industry. I have used huge numbers of methods of connection including
crimped and soldered joints in cable sizes ranging from 0.32mm2 to
300mm2.

Which cables use soldered on terminals these days?

Where did I mention soldered *terminals"?

The OP was asking a question that could be answered by suggesting
soldered *joints*.

The principle is the same, I'm afraid. I've never seen a car loom made
with *one* cable to another which means to me it's not ideal for repair
work either. Although of course anything can 'work' including twisted
wires insulated by sellotape.

Are you saying you have never seen a car loom which has in-line soldered or
crimped connections done by the manufacturer?

If so, this suggests that you have not looked at the wiring of many cars...


I spent a large amount of that time designing and building bespoke
control panels for my employer. Part of my job was, in consultation
with others, to specify a standard for external contractors to use
when supplying equipment that needed a control panel, and to check
compliance with that standard. We specified pre-insulated A-MP crimps
(now sold by Tyco) for everything that needed a lug or in-line
connection, and insulated bootlace ferrules for everything else.
Those of us who did this had a combined experience in the electrical
field of perhaps 60 or more years. We never had cause to doubt our
decisions...

So you're simply backing up what I said - you use proper crimps for
the job. I sincerely hope you've never specified these universal
pre-insulated types. The only equipment I've them used on was poorly
made US stuff where I'd guess they were converted for UK use on a
small scale.

I did indeed specify pre-insulated crimps; I just said so in the
paragraph above you are replying to!

Crimped joints and lugs were invented and patented by an American
company; Aircraft and Marine Products. (A-MP.)

Their products, including the pre-insulated ones, carry MIL
certification amongst other things, so I'm sure they will be entirely
capable of satisfactorily joining the OP's car radio connector!

Do they ever specify a pre-insulated connector which 'suits' a variety of
cable sizes? Like the sort most would use for car repairs? I somehow doubt
*that* meets MIL specs.

Go browse the RS website. Search for MIL crimp. You will find that many Tyco
pre-insulated, *multi-sized* Tyco crimp products do indeed meet a MIL
specification.

I can guarantee that you will not pull off a properly made crimp of
any type that has been applied to A-MP standards. The cable will
break first!

You seem to be deliberately moving the goalposts. *I'm* the one saying
that a properly made crimp is the ideal. But that I've seen plenty of
pre-insulated types that simply pull off the cable despite being
apparently made with the correct crimping tool. And that if you
examine the business part by removing the insulation you'll see why -
they are not properly crimped when the smallest cable they say can be
used is. If the cable is the maximum size the results are better.

I have never questioned the suitability of crimped connections for use
in the automobile industry; in fact I've championed it on usenet. I
merely pointed out that for some reason, they are seen as unsuitable in
the motor trade. This is what I said earlier in my reply to the OP:

"For some reason, the motor trade favour soldered joints insulated with
heat shrink sleeving.

What the motor repair trade for whatever reason 'favour' should be of
little interest here - given their near universal appalling standards of
electrical work. Have you ever examined any?

Lots. Some good, some bad. Just like all work I look at done by the motor
trade...

This is out of step with the rest of the electrical world, where
soldered joints are considered at best a bodge, at worst a breaker of
regulations.

Whichever method you use, if done properly it will be reliable."

I have never, ever seen a pre-insulated crimp joint that I have crimped,
or any done by an electrical tradesman, fail where the wire can be
pulled out.

I'll ask you again to try my test using red pre-insulated terminals and
0.25mm² flex using your favourite correct crimping tool. Remove the
insulation and apply a steady pull between terminal and cable. See where
it gives. Do the same a couple of times.

I've used exactly those terminals, with exactly that sized flex, perfectly
satisfactorily on many, many occasions. It's a common cable size for
industrial sensors, of which I've wired more than I like to remember.

If a terminal is fitted to the correct size wire, with the proper tooling,
it can't pull out. It is cold welded to the terminal. That is the principle
of crimp tooling.

That's not to say that I haven't seen it happen where amateurs have
attempted such a joint without the correct skills or tooling. That
doesn't make the crimp joints faulty...

With a quality ratchet crimp tool it shouldn't be possible to get it
wrong. But it happens all too frequently with these universal
pre-insulated types.

It may have happened to you. I've used them for something like 40 years, and
it hasn't to me...

Chris

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