Re: Brass/heat/?

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

Original poster: "Dr. Duncan Cadd by way of Terry Fritz <twftesla-at-qwest-dot-net>" <dunckx-at-freeuk-dot-com>

Hi Ed, All!

>My other electrode option is the OFHC copper mentioned in my other
post, and
>these are in the form of optical flats (diamond machined) that are 2
inches in
>diameter X 1/4 inch thick (and flat to within 2 micro-inches, but
that flatness
>will change within the first few seconds!).


Oh my, you got lucky :-))))  These would make a very nice multiple
gap.  I know copper is a real pain to machine, if you have the means
to do it you could make a sealed "quenched gap"
(http://home.freeuk-dot-com/dunckx/wireless/quenched/quenched_gap.html)
but even if you can't, these disks as-are will still do an excellent
job.  The problem I have found with brass is that the zinc in
particular tends to volatilise under the intense spark heating, and it
then reacts with the oxygen in the air forming dark crud on the
electrodes.  This can be a bit of a bind, but copper (though not crud
free) should be a worthwhile improvement.  I used brass in my quenched
gap, but the seals leak a little and the crud does build up over time.
The heat conductivity side of things isn't such an issue IMHO, it's
simply the effects of localised spot heating at the actual place where
the spark strikes, leading to zinc loss, which causes the trouble.
Even for long runs, the electrodes themselves are not that hot to the
touch (but mine do have substantial cooling flanges).

Dunckx
Geek #1113 G3