Re: Ignition coil abuse


    Before going to the trouble of trying to make a bi ol' HV bushing, try
this:  Put a big (1 1/2") steel bearing on the top and then put a screw or
something on top of that to act as a breakout point...  Then again, neither
the HV bushing or the "anti-corona sphere" may do the trick.  I've punctured
through 1/4inch thick epoxy with an arc from my ignition coil.  If you would
like better control of the output, you'll probably have to take the coil out
to it's case and either pot it in epoxy (not good if it dies) or high
voltage oil.  That way, you can keep the terminals farther away and in oil
to boot.
I'm thinking of trying for the GMHEICSLR cup, myself.  I got some huge mean
power arcs from discharging a 450 volt, 1800 uF cap into my coil.
Anywhoo, good luck

----- Original Message -----
From: Tesla List <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Saturday, April 29, 2000 6:46 PM
Subject: Ignition coil abuse

> Original Poster: "sundog" <sundog-at-timeship-dot-net>
>     Hi all (again!) :))
> Well, the rotary idea is simmering as I dig up info on converting a
> motor to sync operation.  Till I have the info, I'm content with a
> simple low-powered static gap on that 4kv30ma nst (love that
> thing!)  Anywho, I got adventurous and set it up like I'm driving a
> normal TC primary, but instead substituted an old ignition coil I
> got lying around.  Yowza.  It hasn't died yet, but it gets a bit
> warm to the touch (no oil bubblin' yet, but I know the insulation
> inside is taking a pounding from the HV more than the heat).  The
> problems and questions...
> I'm running a 4kv30ma nst, using 15nf of 17.6kv MMC (trying to
> avoid resonance for the moment), across a single static gap.  The
> gap 'trodes are copper pipe (2", all I had!), set the width of a
> hacksaw blade.  The system runs beautiful, not TC like, but gives
> *very* pretty and intense white-hot sparks. I don't assume it to
> have a very long life in this kind of service tho...I'll be a
> little sad when it dies on me. *sniff*
> Now, the nst is 120watts (4kv*30ma).  The gap is around .75-1mm
> (measured at 1 side, and the spark jumps all over the entire width,
> so it's parallel I assume).  What is the firing voltage, and
> knowing the firing voltage, how do I find out how much bang I'm
> dumping into the ignition coil?
> Also, I can't get a good "spark to grounded wire" going here,
> because the sparks will crawl over the nose of the HV output to the
> terminals (not too good for my caps and NST), so I'm trying to
> eliminate that. But no matter what I've tried, as soon as the
> distance to the grounded wire approaches the distance from the
> inner electrode in the HV out of the coil to either terminal, it
> arcs over on me.
> Also, when it's running and arcing to the terminals, I'll get a
> really loud *pop* every once in a while.  I always kill it and
> check for damage to the caps, but find none.  The sound originates
> from the arc from the HV on the coil to the terminal.  Is it
> dumping the cap energy *there* as well as across the normal spark
> gap? (this only happens when the arc is hitting both input
> terminals on the coil) :(  All in all, it's fun as heck! And
> *really* good for the ozone layer ;)  Fans on over here to air it
> out.
>     Do I need to epoxy a HV bushing to the top of this thing so the
> arc will have longer to creep?  I'm also scrambling to dig up good
> HV diodes to charge a DC system.  :)  Think of this as scrambling
> to follow the rather steep learning curve to become competetive in
> Thanks for your time & info
>                                             Shad (aka Sundog)