[TowerTalk] Info/Advice re: Exothermic Welds

Tue Aug 21 17:21:45 EDT 2012

The Erico website and their Cadweld catalog contain a wealth of information
on their products:

http://www.erico.com

http://www.erico.com/public/library/fep/LT0355.pdf

They even have a jig to prevent wires from moving.

Until I looked through the catalog, I wasn't aware that they had molds for
rebar. Had I known, I might have gone that route instead of using mechanical
clamps on the rebar in my Ufer ground.

I used many one-shot molds for grounding towers and my single-point ground
with good success. Never had problems with molten metal leaking out of the
molds, probably because I used very large gauge wire: stranded 1/0. Speaking
of stranded wire, I think it's interesting that the conventional wisdom on
this site is to use #2 solid conductor, while virtually all of the
illustrations in the Erico catalog show stranded wire.

Out of dozens of connections, I had ignition failures on maybe two or three
charges. They pack the igniter dust into the bottom of the charge capsule
and you have to be careful when dumping the charge into the mold not to mix
the charge and the igniter. You should slowly pour the charge into the mold,
then lightly tap the capsule to deposit the igniter on top of the charge. A
good bit of igniter has to be directly under the hole in the mold cap to
capture a spark from the flint gun.

I also bought a 4-wire reusable mold for several spots where I had more than
two wires converging. The mold takes a larger, more expensive charge, so it
was still cost effective to use the one-shots for all the 2-wire
connections, and a lot more convenient.

When I did my second tower in 2007, Erico was selling a new kind of one-shot
mold made of Styrofoam. It was very similar to a Styrofoam cup with a
special lid with a hole in the middle to ignite the charge. I had all kinds
of trouble with those molds, keeping them level, keeping dirt out of them,
having them break, lighting the charge, etc. I had some ceramic molds left
over from my first tower project in 1997, and had much better results with
those. Looking through the Cadweld catalog, it appears that Erico has
discontinued the Styrofoam one-shots. Good!

That said, when I first saw the One-Shot Plus molds, I thought they were
made of Styrofoam -- they look exactly like the Styrofoam one-shots. But it
appears that they're made of ceramic, and are designed to be used with their
electronic igniter and new ignition system. That system would be great to
have, but I'll bet it's much more expensive than the old flint gun --
probably only a good idea if you have ton of connections to make.

73, Dick WC1M

> -----Original Message-----
> From: ve4xt at mymts.net [mailto:ve4xt at mymts.net]
> Sent: Monday, August 20, 2012 7:55 PM
> To: ersmar at verizon.net; knowkode at verizon.net; towertalk at contesting.com
> Subject: Re: [TowerTalk] Info/Advice re: Exothermic Welds
> 
> 
> I would also recommend ensuring the wire is secured from movement before
> letting off the charge.I had one wire get blown out of the mould by the
> charge. The putty Gene and Jim mentions might hold it in, but a brick
> over the wire to keep it from moving wouldn't hurt.
> 73, kellyve4xt
> 
> > From: ersmar at verizon.net
> > To: knowkode at verizon.net; towertalk at contesting.com
> > Date: Mon, 20 Aug 2012 19:14:58 -0400
> > Subject: Re: [TowerTalk] Info/Advice re: Exothermic Welds
> >
> > TT:
> >
> >      I second Jim's recommendaton about using electrician's putty to
> > seal the holes in the Cadweld Oneshot molds.  I didn't do that for the
> > first shot I fired and lost most of the liquid charge into the dirt.
> > The second and all subsequent charges went well for me after I used
> > the putty, especially underneath the mold where the ground rod
> penetrates.
> >
> >      As an aside, I had expected a lot of fireworks when the shot went
> off.
> > I was disappointed - it was mainly smoke and very little flame.  Stay
> > upwind!
> >
> >
> > 73 de
> > Gene Smar  AD3F
> >
> >
> > ----- Original Message -----
> > From: "Jim Hoge" <knowkode at verizon.net>
> > To: "towertalk" <towertalk at contesting.com>
> > Sent: Monday, August 20, 2012 5:00 PM
> > Subject: Re: [TowerTalk] Info/Advice re: Exothermic Welds
> >
> >
> >
> >
> > Art,
> >
> > Cadweld is one product, made by Erico. Thermoweld is another. Erico
> > calls their single use products Oneshot and yes, the ceramic mold can
> > remain after the fact. One shots are cheaper up front because you are
> > not buying the molds and the handles. A different mold is required for
> > each different application, ie: one wire #4 to ground rod, 2 wire to
> > rod, a #2 wire to ground, etc. I know Thermoweld makes products for
> > flat strap to rod or plate. One note on the Cadweld Oneshots- the wire
> > openings on the molds are a bit oversized and weld material can run
> > out. If you wrap the mold with electrician's putty, it will remain in
> > place long enough to prevent the runout. The thermite weld mix lights
> > very easily with a flint igniter. I was surprised the first time I
> used it.
> >
> >
> > 73,
> > Jim W5QM
> >
> >
> >
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> >
> >
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