RE: Polish the Gap

["Mike Doyle" <mdoyle-at-xxxxxxxxxxxxxx> (by way of Terry Fritz <twftesla-at-xxxxxxxxxx>)]

John - 
A word of caution,  in my experience switch contacts are not made from pure
silver unless they are to be used in a low current application. Pure silver
has to low of a melting point and would cause contact welds in a high
current switch application. Generally something is added to the silver such
as cad oxide.
Cadmuim is considered toxic and I would be concerned about its release if it
was used in a spark gap.

You could try scraping or cutting the contacts - pure silver is very soft
and can be cut or scraped easily but when mixed with cad oxide becomes much
harder.

Michael Doyle - Senior Lab Technician
Cherry Electrical Products
11200 88th Ave, P.O. Box 581913
Pleasant Prairie, WI  53158-0913
Phone: (414) 942-6627
Fax: (414) 942-6334
EMAIL: mdoyle-at-cherrycorp-dot-com <mdoyle-at-cherrycorp-dot-com> 
http://www.cherrycorp-dot-com/ <http://www.cherrycorp-dot-com/> 


	-----Original Message-----
	From:	Tesla list [SMTP:tesla-at-pupman-dot-com]
	Sent:	Wednesday, November 01, 2000 7:47 AM
	To:	tesla-at-pupman-dot-com
	Subject:	Re: Polish the Gap

	Original poster: "John Philip Sanderson"
<John.Sanderson-at-eng.monash.edu.au> 


	----- Original Message -----
	From: Tesla list <tesla-at-pupman-dot-com>
	Date: Wednesday, November 1, 2000 1:34 am
	Subject: Re: Polish the Gap

	> Original poster: "Albert Hassick" <uncadoc-at-juno-dot-com> 

	<snips>

	Dear Al, 

	Thanks very much for your detailed explanation of the static gap.  I

	really like the idea of using cable lugs to mount the electrode 
	material. -A great basis from which to try all manner of different 
	electrodes, as you clearly have done.  Your comments about tungsten 
	carbide also agree with Marc Metlica's observations, that this is
indeed 
	a good SG electrode material.  Since I have so many of these little 
	silver "buttons" from contactors, (I am now reasonably certain that
they 
	are solid silver), I will give them a go in a small series gap for
my 
	little 15/60 setup, replacing the carriage-bolt arrangement I
currently 
	use.  In the next incarnation of my 5kVA beast, I'll give tunsgsten 
	carbide a try.

	And since we're talking SG electrode materials, I guess I should
also 
	take a peek inside my old electrosurgical cutting machine (yet
another 
	interesting Tesla coil application) to see what sort of gap material
was 
	used by the manufacturer.  Of course, power levels in that thing are

	pretty low, but I think the spark-gaps would have been fairly
robustly 
	designed.  (I wouldn't expect any doctors to be opening it up in the

	surgery to clean the gaps!)

	Cheers, 

	John.