[TowerTalk] Info/Advice re: Exothermic Welds

Tue Aug 21 17:36:08 EDT 2012

I purchased Erico/Cadweld One Shots about 18 months ago. They were all
electrically ignited and used a plastic foam cup made from plastic foam
denser than typical Styrofoam. I had no problems with anything slipping
because I made all connections below grade and made sure connections were
mechanically rigid before ignition... that isn't difficult with stranded
#2, it's pretty stiff. I made 7 beautiful connections, including the one
connecting my service entrance to a new 8' ground rod bonded to the
grounding system. When I was done they were all-but already buried. The
code inspector had me dig one up and asked me why I didn't use clamps...

Electrical ignition is the way to go. Copper/thermite particles can cause a
nasty burn, I'm happy to be 6' away when it goes off.

73,

Mickey N4MB

On Tue, Aug 21, 2012 at 5:21 PM, Dick Green WC1M <wc1m73 at gmail.com> wrote:

> 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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-- 
Mickey Baker, N4MB
Fort Lauderdale, FL
*“Tell me, and I will listen. Show me, and I will understand. Involve me,
and I will learn.” *Teton Lakota, American Indian Saying.