From: Duncan Wood on
On Sun, 29 Jul 2007 09:40:32 +0100, Dave Plowman (News)
<dave(a)davenoise.co.uk> wrote:

> In article <op.tv6thdkeyuobwl(a)lucy.gnerwifi.train>,
> Duncan Wood <newsto(a)dmx512.co.uk> wrote:
>> > Indeed. A properly designed terminal crimped properly with a proper
>> > tool is ideal. Those red blue and yellow devices satisfy non of those.
>
>> Well the CEGB used to happily use AMP CertiGrips. PIDGs aren't unusual
>> either. Of course if you're buying cheap nasty ones then you'll get
>> what > you paid for.
>
> On what type of cable? I stated earlier they work ok on solid core or
> stranded mains cable - just not on flexibles as used on cars.
>

Flexible fine stranded cable

> I'd really suggest you make a few trial ones on car cables of various
> sizes then cut off the insulation and look at the result. A good crimp
> grips the cable all the way round - which requires a 'heart' shaped crimp
> formed by the tool. These are simply flattened.
>

Use the right tool then. If it's simply flattened then you're using some
piece of junk you got for �15. & use the right size, the blue ones are for
2.5mm2, not 1mm2 etc. Personally I tend to use the uninsulated ones as
they're a factor of 20 cheaper.

> The other thing is I dislike the look of them. They look like the bodge
> they are. The proper connectors as used by the makers of looms are easily
> available by mail order as are decent crimp tools. While I can accept a
> one off use by an amateur of these easily available crimps there's no
> excuse for pros using them.
>

From: Conor on
Chris Whelan wrote:

> When the solder lug is fitted, or a soldered joint is made, solder creeps up
> the cable by capillary action. This turns a flexible cable into a solid
> one. If subjected to frequent movement or vibration, the *cable* will
> break, usually at the point where the solder has stopped flowing into the
> cable. The industrial situation I was quoting would not be found in the car
> world.
>
Ahh...that explains it. I've never come across it but in the videogame
and automotive market, I guess I won't.


From: moray on
>> Well if they make that bad a connection, then why do the big car
>> manufacturer's recommend them for wiring repairs, and use them when
>> contructing looms?
>
> The answer is they don't use them when making looms. Nor have I seen any
> of them recommend them for repairs. Looms don't usually need any repairs -
> and a maker would recommend replacement if accident damaged.

How do you think they join several wires together in wiring looms?
Manufacturer's generally recommend looms be repaired in service, due to the
uneconomical cost of replacing complete looms, although the germans hate
repaired looms, and will always advise complete replacement.

>> The main thing is to use the right one for the given wiring size (far
>> too many people just use blue crimps, when they should really be using
>> red ones), and to use a good pair of crimping pliers.
>
> There is no right *one* - they all cover a range of cable sizes which is
> the main problem.

But if you use the correct size that covers the wire you're joining, then it
will provide a satisfactory crimp.

>> They're a far better option than using uninsulated crimps, where you're
>> effectively putting an extra connection into the wiring loom, which is
>> likely to cause far more problems than a fully sealed crimp connection.
>> Plus, they don't take up that much room.
>
> I'm not quite sure what you mean. A proper uninsulated terminal designed
> for flex is the correct way - and the same as the makers use. You can
> examine the quality of the crimp too - something impossible with the
> insulated type unless you remove the insulation. And if you do you'll see
> what a mess they are.

By using the 1/4" connectors that you've suggested, you've just put an extra
joint into the loom. Not only that, but it's not a fully sealed connection.
On a vehicle interior, it'll be fine, but on the exterior, water will get
in. And if water can get in, it will corrode. On a power wire, it'll take a
long time for the corrosion to become bad enough to cause problems, but on a
sensor or CAN wire, it doesn't take much corrosion to cause problems.
Also, if you join say 6 wires by putting in 1/4" terminals, one 1/4"
terminal will take up the equivalent room of about 6 (probably more) wires,
so instead of having a loom 6 wires big, you've got one equivalent to about
36 wires big. Off course you can stagger the connections, but they'll still
take up alot of room, which is usually at a premium on modern vehicles,
meaning you'll struggle to get trim panels back in place.
The heat shrink butts don't add that much to the size of the loom in
comparison, and only take up slightly more room than a soldered connection
with heatshrink over it.

>> I've fitted hundreds of the above mentioned crimps, and have never had
>> any fail. I'll admit I've not crimped some correctly, that's why I
>> always try pulling them apart before shrinking them to check they're
>> crimped correctly.
>
> Oh they may well 'work' for a time. But nothing like as long as a properly
> made crimp will. And there's no need to try pulling a proper crimp apart -
> you can see if it's properly made.

Well considering we've got several recovery lorries that had the original
rear light looms (which lasted about 18months) repaired with heatshrink
butts, and they're still working perfectly 4 years later, in what's about
the worst enviroment for wiring on vehicles (fully exposed to road spray,
with minimal support), you can't really say they're not upto the job.


From: Dave Plowman (News) on
In article <op.tv72xrsfyuobwl(a)lucy>,
Duncan Wood <newsto(a)dmx512.co.uk> wrote:
> > I'd really suggest you make a few trial ones on car cables of various
> > sizes then cut off the insulation and look at the result. A good crimp
> > grips the cable all the way round - which requires a 'heart' shaped
> > crimp formed by the tool. These are simply flattened.
> >

> Use the right tool then. If it's simply flattened then you're using some
> piece of junk you got for �15. & use the right size, the blue ones are
> for 2.5mm2, not 1mm2 etc. Personally I tend to use the uninsulated
> ones as they're a factor of 20 cheaper.

All the pro crimp tools for RG&B pre-insulated terminals simply flatten
the terminal - regardless of the pretty pattern they leave on the
insulation. I'd suggest you actually examine the terminal crimp by
removing the insulation.

Red pre-insulated are said to be suitable for 0.65 - 1.5mm� cable
Blue 1.5 - 2.5mm�
Yellow 3 - 6 mm�

BTW - I don't use junk crimping tools. They are pointless. The one I have
for *proper* car terminals cost over 70 quid. Pre-insulated terminal
crimpers - even decent ones - tend to be considerably cheaper due to
economies of scale. The most expensive crimping tool I have for specialist
small terminals cost over 200 quid.

--
*Horn broken. - Watch for finger.

Dave Plowman dave(a)davenoise.co.uk London SW
To e-mail, change noise into sound.
From: PC Paul on
Dave Plowman (News) wrote:
> In article <op.tv72xrsfyuobwl(a)lucy>,
> Duncan Wood <newsto(a)dmx512.co.uk> wrote:
>>> I'd really suggest you make a few trial ones on car cables of various
>>> sizes then cut off the insulation and look at the result. A good crimp
>>> grips the cable all the way round - which requires a 'heart' shaped
>>> crimp formed by the tool. These are simply flattened.
>>>
>
>> Use the right tool then. If it's simply flattened then you're using some
>> piece of junk you got for �15. & use the right size, the blue ones are
>> for 2.5mm2, not 1mm2 etc. Personally I tend to use the uninsulated
>> ones as they're a factor of 20 cheaper.
>
> All the pro crimp tools for RG&B pre-insulated terminals simply flatten
> the terminal - regardless of the pretty pattern they leave on the
> insulation. I'd suggest you actually examine the terminal crimp by
> removing the insulation.
>

http://www.molex.com/tnotes/crimp.html

No way can a 'flattening' crimp tool achieve a good crimp - the best you
can hope for is a crimp that you can't just pull off with your fingers...

The other problem with the preinsulated types is that you can't see the
actual crimp - I've seen many joints where the only electrical contact
is where the connector has just about been squeezed so hard it pierces
the insulation that it's crimped onto.


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