Re: Tungsten-carbide results

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Peter Lawrence by way of Terry Fritz <twftesla-at-uswest-dot-net>" <Peter.Lawrence-at-Eng.Sun-dot-com>

Guys,
     I have built a static gap using Tungsten-Carbibe "balls" silver soldered
to brass screws. It works really great compared to brass, which tends to
oxidize quickly and go south.

I tryed this because in trying to measure the output of my various coils
(different wire sizes on the same size coil forms) I found that the most
significant cause of spark output was the condition of the spark gap, not
the coil. A clean brass SG (cleaned up with a green Scotch scouring pad) 
had TWICE the spark length as a dirty one. Having to clean the SG between
every change I made to measure various other effects was getting tedious!!!
So far I have not had to clean my Carbide SG even once since I made it!!!

I ordered 8 Tungsten Carbide balls from SmallParts Inc (www.smallparts-dot-com)
3/8" diameter, and made 3/8" diameter ball shaped depressions in the phillips
heads of some 1/4-20 screws with a "ball end mill" (but you could problaby 
make do with a counter-sink drill bit or whatever),  and silver soldered them
together.

The nice thing about the Carbide balls is that they come machined and polished,
you don't have to do anything to them.

I was leary of trying this because Carbide is not pure (I think pure Carbide
is actually more of a ceramic than a metal) but Carbide as we know it is
really powdered Carbide held together by Cobalt. In any event it works
really well. I wanted to use pure Tungsten, but have not found a source
for Tungsten balls, and machining balls from Tungsten rod is not my idea
of fun (Tungsten is much to brittle to machine, it would have to be ground
with a toolpost grinder, and I absolutely hate putting anything abrasive 
anywhere near my lathe).

I put 4 gaps in electrical series but mechanically they are in parallel, and
I have nylon screws/nuts holding the plastic plates together (springs keep
them appart).  The nylon screws/nuts allows for adjusting the gap by
thousandths of an inch while the TC is running, and makes things very very 
nice! Some day I'll put up a web site with pictures (worth a 1000 words...). 

I will also be trying a single gap with two 1/2" balls soon, I'll let you
know how it compares.

Carbide balls are very expensive, but IMHO, very worth it.

-Pete Lawrence.