"DoN. Nichols" wrote:

According to Joseph Gwinn :
In article ,
(DoN. Nichols) wrote:

[ ... ]

And for the larger terminals -- 8 through 2 Ga, and 1/0 through
4/0 -- I have an electrically powered hydraulic system.

I had to attach two terminals to #6 stranded wire many years ago, in the
late 1960s. There wasn't space for a mechanical (sidebolt) terminal,
and I didn't have a crimper, so I bought the crimp terminals (which were
made of copper) and simply soldered them to the wire with a torch and
plumbers solder and flux, wiped the flux off with a paper towel, and
insulated the barrel with heavy heat-shrink tubing.

That can work -- but it can be a bad choice if the terminal is
subjected to vibration. The solder wicks up to the insulation and stops
right there, and any flex from the vibration is concentrated in that one
spot -- resulting in eventual failure at that point.

The crimped terminals leave a bit more length of solder-free
wire, so the flex occurs over a longer stretch, and the wire lasts
longer.

And the *good* crimped terminals -- the pre-insulated ones with
a P.I.D.G. crimper will collapse the rear of the insulation sleeve to
grip the insulation, thus reducing the flex at the terminal. In
particular, the AMP terminals for the P.I.D.G. (Pre Insulated Diamond
Grip) have a sleeve of metal shim stock around the terminal barrel and
inside the insulation, with the last bit folded back to the edge points
towards the terminal. This bites into the insulation to grip it more
firmly than possible by just collapsing the plastic insulation to form a
grip.

This is why these terminals are particularly preferred for
aircraft applications -- when it is quite awkward if certain electrical
connections fail while you are aloft -- and they *never* seem to fail
on the ground. :-)

Enjoy,
DoN.

--
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In my experience, the biggest problem with failure of crimped terminals
is that the installer did not use a proper crimping device, or the unit
was not calibrated with a go no go gauge. The cheap stamped out
crimping might be ok for household use but they spring and don't do a
secure crimp. A good T & B forged crimping tool is a lot better way to
go than the stamped ones if you can find one used in good shape. The
best crimpers are the ones that have a racheting system that will not
release until the proper pressure is put on the crimped terminal, but
these crimping tools must be checked periodicly with a go no/go gauge.
Overcrimping is as bad as under crimped terminal. Overcrimping cuts the
wire and although the terminal looks like a good crimp a number of wires
are cut and the terminal is held on mostly by the insulation. On the
high end crimping tools, there are identification marks that are on the
crimper that leave the same mark on the crimped terminal so the
inspector can tell if the terminal was crimped with the right tool.


John