RE: Copper VS Steel

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Lau, Gary" <Gary.Lau@xxxxxx>

Hi Jim:

Answers/comments interspersed below:

> Original poster: Jim <branley1@xxxxxxxxxxx>
>
> Hi Folks:
> I do appreciate the great assistance with my tesla coil that I have
> received from you.
> Can I get your opinion on a few things?
>
> 1) Can I use 1" EMT (Electrical Metallic Tubing) for my spark gap
> instead of 1" copper pipe?

Copper is better for several reasons.  Copper is thermally more
conductive than steel and will more rapidly remove the heat from the
point of the arc, aiding quenching (see below).  Additionally, the zinc
coating has a very low melting point and would very rapidly burn and
erode away.

> 2) Can I use zinc coated bolts and nuts for my secondary instead of
> brass bolts and nuts? Zinc is what most bolts, nuts & washers are
coated with.

Absolutely.  Secondary current is very small and any additional
resistance posed by steel/zinc vs. brass is negligible.  Also, many
suggest that ferrous-based hardware should be avoided near the primary &
secondary, but I don't believe that such small objects would make any
difference.

> 3) What does the term quenching refer to when speaking about spark
gaps?

That's a long storey.  The word refers to the point when the spark gap
stops conducting - when it "quenches".  It sounds simple enough, but
it's something that we're still unable to predict or precisely control.
Ideally we'd like the gap to quench as soon as all of the primary energy
has transferred to the secondary.  This would be called "first notch
quenching".  If the gap continues to conduct beyond this point, the
energy now in the secondary will swing back and couple back into the
primary, and then it will go back to the secondary, etc, until the gap
stops conducting.  We know certain things impede quenching, like high
pri-sec coupling, and poor gap design.  If gap electrodes get very hot,
if the electrodes are pointy, if they're made of materials that vaporize
easily, if ionized gasses remain in the gap, these all hurt quenching.
Richie Burnette has a superbly illustrated web page devoted to this
topic; please see
http://www.richieburnett.co.uk/operatn2.html#quenching.  Than you Richie
for getting that back on line!

> Thanks for the informative help!
> Jim

Regards, Gary Lau
MA, USA