Re: construction materials

["Bert Hickman" <bert.hickman-at-aquila-dot-com> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Tesla list wrote:
> 
> Original poster: "Bill Lemieux" <gomez-at-netherworld-dot-com>
> 
<SNIP>
> > I've seen some nice tungsten
> > electrodes, but aparently they are hard to machine, and quite expensive.
> 
> Check out your local dart shop.  If you have access to a machine shop, then
> tungsten is no harder to machine than steel.  If you don't have access to a
> machine shop, it doesn't matter does it?
> 
> > However, I was leaning more towards brass. Does this stand up well to TC
> > abuse?
> 
<SNIP>

Great post, Bill. However, there may be a possible health risk in using
darts, since the barrel of so-called "tungsten darts" are actually made
from a tungsten-nickel alloy that contains typically 10-30% nickel. For
a variety of reasons (machinability, brittleness, cast), no dart barrels
are made from 100% tungsten. 

The possible health risks of using these are similar to concerns
previously voiced on this list. Similar objections exist
against using stainless steel alloys for high-power spark gap
electrodes. Since some metal is likely to be vaporized or oxidized in
operation, these byproducts may then be accidently inhaled. The Material
Safety Data Sheet (MSDS) for nickel lists it as a possible
cancer-causing agent (a carcinogen), and similar warnings apply to
chromium. Nickel's green and black oxides(Ni II, Ni III) also have
similar MSDS warnings, along with chromium oxide. If you do decide to
use darts as electrodes, you may want to also use an exhaust fan to keep
from accidently inhaling metal or oxide particles. 

On the other hand, pure tungsten is not listed as a carcinogen.
However, thorium oxide (added to make 2% thoriated tungsten welding
rods) adds an unnecessary degree of risk, since thorium oxide is also a
known carcinogen. There are strict rules regarding machining thoriated
tungsten, requiring the use of respirators, and the waste material must
be disposed of as a low-yield radioactive material. The welding industry
recognizes the risk and is actively looking for safer alternatives, such
as other rare earth metals. Using thoriated tungsten adds no benefit
when used in a high-power Tesla Coil spark gap, and it may actually
reduce your gap's ability to quench versus using pure tungsten rod. For
a variety of reasons, try use pure tungsten if at all possible in your
rotaries...

Safe coilin' to you!

-- Bert --
-- 
Bert Hickman
Stoneridge Engineering
Email:    bert.hickman-at-aquila-dot-com
Web Site: http://www.teslamania-dot-com