[TowerTalk] One Shots

[David Gilbert]

As far as I know the reusable molds are graphite, not ceramic, but if 
you can find a used one is good shape it would be far cheaper to go that 
route.  You can often buy the powder on eBay for peanuts, which is what 
I did.  The typical mold for connecting #4 solid wire to a 5/8" ground 
stake uses about 65 grams of powder, so I bought 200 gram shots and 
divided them up into thirds.  You just need to be careful when doing 
that so that you save some of the finer starter powder for each of the 
thirds.

The availability of Cadweld powder on eBay is pretty sketchy, though ... 
sometimes you see a bunch of it and other times very little. When I 
installed my tower eleven years ago I was able to buy powder for the 
equivalent of 55 cents per shot, but the cheapest I see at the moment 
works about to more like $3.00 per shot.  A few months ago I saw some 
for about $1.50 per shot.

Finding the right mold used in good condition is even harder, but for 40 
shots even a new mold is cheaper than a bunch of one-shots. Don't bother 
with looking for a Cadweld mold clamp ... there are cheaper and simpler 
ways to hold the halves together.

Graphite is easy to work using wood tools, so I even made my own mold 
(don't breathe the powder!) ... check out:

http://www.ab7e.com/exothermic/AB7E_Homebrew_Exothermic_Mold.html

In a fit of mad scientist stupidity, I once tried making my own powder.  
The stuff is basically the aluminum version of the iron thermite used to 
weld railroad tracks and burn holes in enemy truck and tank engine 
blocks.  Cadweld powder is copper oxide and aluminum powder that 
converts to copper and aluminum oxide (ceramic), in the process 
generating a lot of heat and a lot of light.  So I bought the powders on 
eBay, figured up the formula for the right proportions, and mixed it all 
up.  Unfortunately, the powder I was able to buy was lab grade stuff and 
very fine.  It went up like the flash powder they used to use for 
photography in the 1800's.  Actual Cadweld powder is more coarse and 
reacts slower and more controlled.  The stuff I mixed would make good 
starter material, though, so I haven't thrown away the components.

By the way, 4th of July sparklers are a good way to fire off the starter 
material.

73,
Dave   AB7E



On 8/27/2019 7:55 PM, Neal Sulmeyer wrote:
> ​While on the subject, rather than using the "one shot" units, has anyone used the  reusable ceramic molds?  I expect to use between 30 and 40 ground rods for my towers and shack ground systems.  It seems to me to be much more economical to use the reusable molds.
>
> Neal, K4EA
> ________________________