On Sat, 14 May 2005 15:35:43 -0700, Larry Jaques
wrote:

On Sat, 14 May 2005 21:42:16 GMT, the inscrutable Gunner
spake:

Portable engine driven DC welder

http://www.motherearthnews.com/top_a..._DC_Arc_Welder

404

Damn..it worked earlier today.

go to motherearthnews.com, go to archives, go to 1980, issue #66 (when
the page loads look for welder for pictures and schematics

Issue #66 - November/December 1980

If you can scrounge an old lawn mower, an automobile alternator, and a
12-volt battery, you can . . .

BUILD A $20 PORTABLE DC ARC WELDER


Given a choice between adding either arc or gas welding to the
workshop, most tinkerers find a small AC arc unit to be an inexpensive
and impressively versatile piece of equipment. However, for those
occasional remote outdoor chores that come up around most farmsteads,
gas is just about the only practical choice. (Of course, there are
portable electric welders available, and one could use a shop unit and
tote along a generator . . . but either approach represents a
considerable investment, especially if the devices will be used only
to accomplish infrequent in-the-field repairs.)

As it happens, MOTHER's researchers run into a fair number of remote
welding jobs out at our Eco-Village property — from tacking together a
windplant frame to sealing a hydroplant pipe — that are just plain
inaccessible to the Lincoln automatic feed unit that they prefer.
Therefore, it didn't take long for one member of our team to get so
fed up with the hassle of loading both a generator and an arc welder
into a pickup truck that he began combining some odds and ends around
the shop to make his own portable welder.

Experimenter Dennis Burkholder decided that — after scrounging up an
old power mower, a set-aside Delco-Remy automobile alternator, and a
weary but serviceable 12-volt deep-cycle battery — he had just about
everything he needed to build a portable, intermittent-duty,
low-voltage, DC welder. Sure enough, after trying a couple of
different combinations of the scrap components, he came up with what
must be the least expensive (and strangest looking) arc welder ever
assembled.

Essentially, the welder is powered by the roughly 50 amps that the
Delco-Remy alternator is capable of producing . . . and is adjusted by
varying the speed of the lawnmower engine. But the 12-volt battery is
needed to balance out those surges that occur when the arc is struck
or broken. Furthermore, Dennis found that the setup worked a lot more
smoothly with two 1-1/2-ohm, 8-amp resistors placed in series with the
field of the alternator, to cut the field voltage to about 6 volts.
(In fact, without the two resistors, striking an arc would nearly kill
the 3-HP Briggs & Stratton engine!)

Considering that the parts for the project are almost all scavenged,
the welder is amazingly versatile. For one thing, DC capability is
often preferred for smooth sheet-metal work, and our lawnmower unit
can have its polarity reversed for changing the penetration and
spatter qualities of its arc! There are, however, a few limitations to
the tool's capabilities. First, the maximum heat of the arc is about
50 amps, so the device won't penetrate more than about 1/4" into
steel. In addition, it's best not to use the welder for more than
about 20 minutes at a time . . . to avoid overheating the alternator
(the thermal overload switch shown in the schematic drawing
automatically tells you when enough is enough).

And finally, the unit's low-voltage DC current presents both an
advantage and a disadvantage over conventional AC power. Because the
voltage of a circuit determines the distance a spark will jump, the
rod used with our portable welder must be held steadily close to the
surface of the work to maintain an arc. But, because it is a
direct-current welder, there's little tendency for the rod to become
stuck.

Of course, the most astounding thing about Dennis's welder is how
little it cost. The only components that our researcher was forced to
buy were the resistors, which he located at the nearest auto parts
store. And — even if your storehouse of valuable discards doesn't
equal MOTHER's — you should still be able to purchase the resistors,
wires, switches, pulleys, and V-belt for less than $20. When you think
about it, a $20 DC arc welder, with a built-in dolly, might be the
workshop bargain of the year!





http://www.green-trust.org/equipment.htm



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