[Towertalk] CadWeld

Kelly Taylor ve4xt@mb.sympatico.ca
Sat, 3 Aug 2002 23:58:23 -0500


Hello all,

Since there seems to be quite a bit of interest in the subject, I thought
I'd pass on my CadWeld tips from a couple of years ago. These tips are based
ONLY on CadWeld OneShot use, but may or may not be applicable to the CadWeld
reusable moulds. (Molds, for those in the U.S.)

1. Buy and use the sleeve, which keeps the top of the ground rod from
mushrooming as it's driven in or be sure to grind the mushroom off before
attempting to install the ceramic mould. When it says it fits a 5/8-inch
rod, it really does fit a 5/8-inch rod. And ONLY a 5/8-inch rod. It will NOT
fit a 5/8-inch rod plus 1/64 of mushrooming. You don't need to buy the $20
(reusable) sleeve, as long as you grind, but if you're doing a lot of rods,
it is probably a worthwhile expenditure.

2. Secure the grounding medium (strap, wire, etc.) from movement before
firing the CadWeld. The combustive process imparts some mechanical energy
into the medium which may otherwise cause it to leave the combustion chamber
and therefore render your effort useless. If the net result of firing the
material is that your wire isn't connected...

3. When the instructions say the CadWeld process will only be ignited by a
spark, THEY MEAN IT WILL ONLY BE IGNITED BY A SPARK. For safety reasons, the
material is formulated with a high enough flashpoint that it won't be
accidentally ignited by other means. The RF Connection sells the spark
ignitor for $5 and change. What's five bucks? That said, I'd be curious to
see if a fireworks fuse would ignite the material. I suspect it would, but I
also suspect that purchasing one piece of fireworks to test the theory would
cost more than $5.

4. Don't be too worried about the combustive process. If you use the same
caution with the ignitor as you would match-lighting a gas grill, you'll be
fine. The process is NOT explosive, merely rapidly combustive. The fireworks
really aren't that impressive, just don't get your face within about two
feet.

That's it. CadWelding is simple and cheap. A two-wire OneShot (say for rods
in the middle of a radial field) is $8. And you never have to inspect and
clean the connection again. A bargain, unless you really get off on
wire-brushing copper wire.


73 all,
ve4xt

Kelly Taylor