[DMCForum] Walt...
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[DMCForum] Walt...



...First off I consider you a good example of self learning. I been
watching and I see your A/C knowledge has come a long way. Plus you
strive to know the finer points. Good for you.

Next, auto-darkening helmets are like everything else: ya gets what
ya pay for. Some claim the time it takes for the slower ones will
cause an accumulated build up of eye damage over many strikes in a day
but the jury is still out on that. Just to be safe get a good one, at
least as fast as 1/25,000th of a second, 1/50,000th is even better.
The Hornel Speedglass is a top notch example. Consider a helmet with 
a variable shade if you do more than one process.

Some helmets are solar powered but mine uses 2 AAAs and has auto
shutoff, some have all those features. GTAW is a clean process due to
the lack of smoke and the concentrated arc radiation is more intense
than it appears. Just cuz there is no splatter doesn't mean you can
TIG is shirt sleeves and forget your exposed skin. This goes for your
neck and arms. Protect them or you'll get a radiation burn over time.
It's like a sunburn for lack of a better description.

I long ago told you how I did the fan fail thing. I'd post it here
but I tend to be as long winded as you are. Due to my combined
experience in engineering and aviation I have an interest in failure
analysis and it always amuses me when people say something is
just "bad" and don't use it. They never say why it's bad or how it
fails. There is always both an indentifiable root cause for failure
and particular failure mode. Define those and you can engineer a
solution.

In the Fan Fail Module it's a simple question of insufficient
ampacity. The sensing portion of the module is not an issue, it sees
peanuts for current. It's the power paths of this inductive device
that fail and those paths can be strengthened in several ways. I
chose to Tig silver plated copper braid in there as I have a 50 amp
torch but one can also beef them up using soldering techniques. For
the less technically inclined the best method is replacement with
something  designed to resolve the issue. For example, John Hervey's
gadgets are a good choice. The Zilla thing is nice too but way
overpriced for someone who can mod the original.

After moding mine I placed it on an electronic load and programed a
5,000 count cycle at 50 amps while measuring the load paths in two
places with thermocouples. Yeah, I know that's a tad anal but it's
why I have complete faith in it. So far so good, two years later it
was working fine.

Of course, a current path is only as strong as it's weakest link and
there are other weaknesses (socket contacts, splices, ect) in the car
we all know about. Much of the electrical stuff in my car was
replaced with higher quality components where I felt it was needed
for reliabilty. As you know, there are several areas of the
electrical system that can benefit from redesign. Some require
attention for safety reasons, the overcurrent protection scheme used
in the D is enough to give even a first year EE student the heebee-
geebees.




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