Re: Tungsten vs. Tungsten Carbide

To: tesla-at-poodle.pupman-dot-com
Subject: Re: Tungsten vs. Tungsten Carbide
From: Benson_Barry%PAX5-at-mr.nawcad.navy.mil
Date: Mon, 25 Nov 1996 11:54:00 -0400 (EDT)

What is a "mini pig"?
Barry

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|From: "tesla-at-poodle.pupman-dot-com"-at-PMDF-at-PAXMB1
|To: Benson Barry; "Tesla-list-subscribers-at-poodle.pupman-dot-com"-at-PMDF-at-PAXMB1
|Subject: Re: Tungsten vs. Tungsten Carbide
|Date: Monday, November 25, 1996 12:55AM
|
|<<File Attachment: 00000000.TXT>>
|From rwstephens-at-ptbo.igs-dot-netSun Nov 24 22:32:34 1996
|Date: Mon, 25 Nov 1996 05:43:25 -0500
|From: "Robert W. Stephens" <rwstephens-at-ptbo.igs-dot-net>
|To: tesla-at-pupman-dot-com
|Subject: Re: Tungsten vs. Tungsten Carbide
|
|>>From mycrump-at-concentric-dot-netSat Nov 23 20:07:58 1996
|>Date: Sat, 23 Nov 1996 20:10:01 -0500 (EST)
|>From: "Daryl P. Dacko" <mycrump-at-concentric-dot-net>
|>To: tesla-at-pupman-dot-com
|>Subject: Tungsten vs. Tungsten Carbide
|
|>I spent several hours today playing around with my arc lamp
|>power supply and some tungsten rod and a tungsten carbide lathe
|>insert to see which faired better in a torture test.
|
|<snip>
|
|>These carbide tips look better all the time !
|
|>Has anyone else tryed carbide tips in a rotary ?
|
|>Daryl
|
|Daryl, All,
|
|I employ tungsten carbide tips brazed to 1/4 inch steel mounting
|shafts as the stationary electrodes in the rotary gap for my MTC
|system.  The pad surfaces are about 3/8ths inch square each and
|radiussed to best fit the travel of the 1/8th inch thoriated tungsten
|rods that fly by on the disk.  I employ a 6.5 amp Lamb vacuum cleaner
|blower with a nozzle directed at each pad to assist in cooling the
|pads below the melting point of the brazing and also for improved
|quenching.  This system works faultlessly at 7 kVa.  The exact same
|system previously has had high carbon steel, and also brass stationary
|electrodes and would literally eat them in just three minutes of run
|time.  I have perhaps 15 minutes run time on the new setup and see no
|detectable wear yet on either the flying tig tunsten electrodes, or
|the thoriated tungsten pads.  It seems apparent that part of the
|trick to extending contact surface life, even with tungsten, is to keep 
them
|cool.
|
|As a further note.  I employ the side of the flying tungsten rods,
|not the end tips, as my contact surface.  This trick reduces the
|current density of the arc and spreads out the wear for longer
|electrode life.  If it is increasing the gap resistance a bit by
|lowering the temperature of the plasma it hasn't hurt performance so
|that I'd notice.  This sytem consitently delivers hot, white, 12 foot
|streamers on just 7 kVa.  Note also that I  _ do not_  employ any
|power robbing stationary series quench gaps in the MTC system.
|The mini pig voltage is 12 kV RMS.  Cap size is 0.125 mfd.  The
|peak primary current being switched by this rotary is indeed very high.
|System energy is something like 17 Joules.
|
|rwstephens
|