[Vwdiesel] Broken Bleeder Valves

James Hansen jhsg at sk.sympatico.ca
Thu Mar 13 10:44:52 EST 2003

Roger sez:

> The stitch welder attachment is just a half wave diode, so gives
> you a 60Hz AC ripple current with every other cycle filtered
> out.  Bascially lets you run a higher voltage for a stable arc
> but cuts the current in half for less heat.  That coupled with
> the very small rods that you need to use with the unit allows you
> to run an AC buzz box on thinner sheet metal.  I recently sold
> the one that I got with my arc welder after I got a MIG.

Oh, so this is a unit on an A/C stick welder?  I get it now.  It would be
MUCH easier to start the arc repeatedly with higher voltage.  Huh, never
seen one here, too many migs for a looong time I guess.

What I was referring to was a feature on some mig welders that allow you to
stitch or skip weld using a timer to control on-off times, instead of using
your trigger finger.  You basically point where you want to start, pull the
trigger, and just keep moving as if you were continuously welding, but the
fire starts and stops, letting you do very good low distortion work on thin
panels. You can do the same yourself with trigger modulation, but the
temptaion to prolong the weld times and get distortion is removed.

Yeah, I just had a look at Eastwood, i see what you are taking about now.  I
had some of these little rods for welding light panels with a/c stick.  Man
you had to be fast.  I can see where the stitch feature would be nice.   How
did it compare to the mig you have now Roger?  I could see some advantages
with the stick welder, being less prep required, rust and paint not as much
of an issue.

Oh yeah, Nate- your prep time is greater with a mig, particularly with gas
sheild.  It does not tolerate weld impurities as well.  This can be
alleviated some by the sheild gas you use, and the filler wire used, but
still is an issue.  If you weld  old rusty iron, d/c stick is still
preferred.  It can certainly be done, but there is some technique that takes
some experience to get on to.

Oh- there is a product called FLAMEX that is a blend of gasses, mostly
propane, that runs hot enough to gas weld with.  You buy it for similar
costs to propane, but it is a tad hotter, and cuts better too, so I'm told.
As I said, I will ditch the acetylene next time the contract is done, and
get propane, or flamex.  I can't bear the though of not being able to gas
weld.  There is a purpose for it which is hard to replace at times, but for
the fiddly little stuff, I guess I still have a jeweler's acetylene setup
and the little bottles. The big tip is pretty hot.
I was told once that propane flame is too oxidizing- or too clean burning to
weld properly. Acetylene is very rich in carbon, even with a neutral flame
there is excess carbon that prevents surface oxidation and slag formation
allowing the steel being joined to flow together.  Flamex has other carbon
sources in it to make it hotter, and more carbon.

On a sidebar, mostly for Harmon, there is a huge diference between a carbide
miner's lamp or a bicycle lamp that dribbles a drop of water every now and
again, to make enough acetylene to support a candle's amount of fire, and an
acetylene generator sufficient to power a torch.  Almost every local town
had a blacksmith at one time.  There are also stories associated with each
town's blacksmith, and usually at least one of these stories relates to how
the shop was levelled by the blacksmith's acetylene generator either
leaking, over-generating to the point of overpressure explosion, etc. You
can buy acetylene in relatively safe tanks in stable form.  This is a
definite advantage.  Discovering the vagaries of acetylene generation would
best be left to someone else.  the level of technology hasn't changed
terribly much from years ago to now.  Controlled dribbling of water on
calcium carbide.  TOo much water, gives too much acetylene, in a brass tank,
mixed with O2.... hmm, you see the result? Happened LOTS in the days it was
the only way to have acetylene.  I have been told a lot of these stories,
being a blacksmith and all.

 Mark, you know at what pressure it does spontaneously oxidize whan mixed
with O2?  I would assume it would have some to do with the percentage...  I
never did subscribe to the 15psi or boom theory either, it makes little
sense, but in the presence of O2, now that I can buy.
However, anyone not running flashback arrestors on their hoses is using a
bomb.  When you first light up, if there is a small leak somewhere, and the
hoses have O2 in them from sitting, it can explode all the way back to the
regulator, which touches off the tank.  Local fellow died a few years back
from just that.  A flashback arrestor screws into the regulator body just
before the hose, to provide a one-way valve so nothing gets into the
regulator. Twenty bucks can save your life.

I've prattled on enough...

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