Jim,
You've got a couple of really good suggestions here. I have everything
needed to do silver brazing, except the bottles, which I can retrieve the
next time I'm in Las Vegas. So this would be a no cost solution.
However, there is one undesirable aspect of soldering lugs that might also
apply to brazing. Solder can wick up the wire and inch or two resulting
in an inflexible cable near the termination. A small thing but it always
bugged me. And then there's the damage to the insulation which could be
great at brazing temperatures. Your other suggestion that I get the
connections crimped at my local welding store has great merit since I
usually buy my lugs there anyway. But maybe the best solution, since I
seem to be fabricating a lot of heavy-duty cables lately, would be to buy
one of these:
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=66150
Dave
At 06:16 PM 3/30/2010, you wrote:
Dave Leddon wrote:
I've been trying to eliminate hot spots in the primary circuit of a
relatively high current (~3000 amp) drsstc by replacing high resistance
connection points with copper. Even a one-inch length of 3/8-inch brass
bolt can generate enough heat to melt the solder right out of a terminal
lug. Which raise another interesting point, what about solder? It has
ten times the resistance of copper so maybe all lugs should be crimped.
I only soldered them because I don't own a crimper large enough to deal
with #2 welding cable. But I digress. I've not had any success locating
a source for copper nuts and bolts, probably because copper isn't strong
enough to be consider a fastener, and so have been force to machine my
own. I would much rather just plunk down the credit card.
Does anybody know of a good source for copper hardware?
Crimping is common for applications like welding cables. Most welding
supply places can crimp connectors on your cable for you.
"hard solder" (aka silver solder) or brazing is another alternative. Much
higher melting point.. Hey, an excuse to use a MAPP/Oxy or Acetylene/Oxy
rig! I've used one of those inexpensive MAPP/Oxy sets with the disposable
bottles to do stuff.. It gets expensive if you use much gas, but for a
small project, it's not too bad. MAPP/SolidOx is another possibility
which is a bit less expensive for supplies.
But if you're going to do more than a simple job, it's worth getting (or
renting?) a real oxy/acetylene rig, like refrigeration guys use, with the
small bottles. About $300 or so, including the bottles and torch. And
brazing/gas welding is actually pretty easy (compared to, say, straight
stick welding) with a very small amount of practice. (as long as you stay
away from aluminum.. it's just hard, because it melts before it changes
color)
Have you looked at "split bolts" used in electrical wiring? They also use
copper hardware for high current applications, so a commercial electrical
supplier might have them.
Copper hardware is also used in the marine industries.
And, of course, McMaster Carr might have them..
But.. what you really want is exothermic welding, aka Thermite. Cad-Weld
is one trade name.
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