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Re: Eight Series Binary Spark Gap Adjustable from .001" - .254" in .001" increments. (fwd)

---------- Forwarded message ----------
Date: Thu, 05 Jul 2007 23:12:58 +0000
From: Jeff Behary <jeff_behary@xxxxxxxxxxx>
To: tesla@xxxxxxxxxx
Subject: Re: Eight Series Binary Spark Gap Adjustable from .001" - .254" in
    .001" increments. (fwd)

Hi Bart,

These gaps were a standard 1920's Tesla Coil gap made by HG Fischer for 
medical, wireless use, and experimentation.  They were damn impressive!  The 
fins were stamped individually and contained a recess for the spacing 
between.  The threaded rods were 5/16-40 - extra extra extra fine 
threads...and the end screws were 3/8 - 27!  Talk about hard to find 
taps/dies!  Victor Machinery Exchange in NY sells them, are a great source 
for other obscure machinist tools too.

The gaps require a lot of work.  I made only one from scratch before, and 
did machine the fins as one solid piece with a parting tool.  I'm looking 
into ways of stamping the copper fins.  Casting is a great idea; we have a 
foundry at my parents house that my grandfather made and have cast 70 pound 
bronze parts before...convincing my Dad to set it up to make spark gaps with 
me is another task - the spot we used is now occupied by a horse and its 
barn!  That foundry would be perfect though for many things Tesla related.

The performance of these original gaps was close to perfect.  A 3-series gap 
with 3/8" tungsten disks (used for Diathermy Machines) could operate a 3000V 
180mA transformer continuously for several hours.  They were espescially 
useful for military hospitals/etc.

The quenching on the gaps is amazing.  One particular X-Ray machine used a 
1000V transformer at 1500mA with a .6 mfd mica condenser.  A single gap of 
this style with 1/4" tungsten was all that was used - which seems 
impossible, illogical, and downright insane but it works!  In this case, the 
gap does get hot after a few minutes, but typical X-Ray exposures from the 
machine were less than 5 minutes in those days.

Virtual Spark Gaps:

Real gaps:

Jeff Behary, c/o
The Turn Of The Century Electrotherapy Museum