Re: solder vs crimp Re: MOT supply construction question

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>




> Original poster: "Jonathan Peakall by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <jpeakall-at-madlabs.info>
>
> Jim,
>
> I have seen this debate  before, but it seems as if the discussion centers
> on solder VS crimping. What are the drawbacks of crimping AND soldering? I
> have seen solder only connections "eject" the wire, I have seen many crimp
> connectors "lose" the wire, but I have never seen a crimp and solder joint
> fail for any reason other than extreme mechanical damage or heat, which
> would have ruined things regardless of the nature of their connection.
>
> Anyway, is there a failure mode that occurs only (or more often) when
> soldered and crimped?

I suppose there are.... although they may not be applicable here..
1) The solder is stiffer than the wire and/or the fillet itself makes a
stress concentration leading to breakage at the edge of the solder.
2) Damage from overheating especially if the thing is relatively massive,
and you don't have suitable soldering gear (of course, the transformer
itself has the winding soldered to the lug, usually...)
3) for temperature cycling.. anything where there's a coefficient of
expansion mismatch you can get little stress cracks leading to increased
thermal and electrical resistance, which aggravates the CTE problem. (This
is the aluminum house wire problem...)

True enough, if you do both, you'll not see the failures due to poor
implemention of one or the other (bad solder or bad crimping)... The real
question is whether it's a bandaid for non-optimum technique or a real
redundancy thing.  Since both techniques, applied properly, are very
reliable, one shouldn't need to do both on the same connection.

To a large degree, I think it's more a matter of craftsmanship than the
inherent quality of the method.  For what it's worth, I am a sloppy
craftsman, so I solder AND crimp, or just do one, and accept failures..
(Alligator clips, masking tape, and twisted wires, or just use air as
insulation and keep the twisted wire connections apart from each other...)

I'll also comment that the technique they teach in "spaceflight qualified"
soldering school is very different than the technique I (and most engineers
I know) use as a hardware hacker.  This is why they don't let me actually
build (or even touch) the flight hardware I design.



>
> ----- Original Message -----
> From: "Tesla list" <tesla-at-pupman-dot-com>
> To: <tesla-at-pupman-dot-com>
> Sent: Saturday, October 12, 2002 11:00 AM
> Subject: solder vs crimp Re: MOT supply construction question
>
>
> > Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> <jimlux-at-earthlink-dot-net>
> >
> > A couple