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Re: Beginner coil thoughts

At 01:29 PM 11/17/98 EST, you wrote:
>In a message dated 11/16/98 9:51:53 PM Pacific Standard Time,
tesla-at-pupman-dot-com
>writes:
>
>- snip -
>
><< 	Removing the core also removes the high coupling from primary to
> secondary.  So you still will not get much out of it.  However, if you now
> tune the primary and secondary to resonance and turn it into a Tesla coil
> circuit, the voltage is then allowed to fly up to the 200X primary voltage.
>  That is what I did and that is why I got very big sparks.  The operating
> frequency is also vasty improved too but the secondary will still limit the
> frequency to the 10kHz range.
> 
> 	This does make the GM HEI coil unique in that the cores are so easily
> removed.  The Mallary, Accell, Jacobs and other fancy rod shop coils don't
> have removable cores as far as I know.  This will eliminate them for my
> uses.  Thanks to everyone that suggested them anyway!
>  >>
>- snip -
>
>Terry,
>
>I am confused about your test.  Your comments above indicate that you did
>remove the core for your testing but in your comments earlier, I believe you
>said you now had to cut the case off to do failure analysis.
>
>Ed Sonderman
>
>

Hi Ed,
	
	GM HEI coils have their primary and secondary windings in a box that is
vacuum impregnated with high voltage potting epoxy.  The steel core is
added later to the outside of the unit.  It is in two E shaped sections.
They are brought together and spot welded to hold the two Es together.  The
steel core is easily removed by grinding out the two spot welds and this is
what I do to used them in my little Tesla coil.  However, when the primary
blew, I had to cut through the epoxy case.  The epoxy clogged and bound on
the SawsAll blade and it was very difficult to do.  If you have never seen
one, it is a little hard to describe.  If you need to see (or get one :-))
just go to any auto parts store and see the ingition coil for a 1983
Cadillac Eldorado with the HT4100 engine.  All these cars used the HEI
system (as well as zillions of other GM cars).  The discount places get
about $15 for them.  I think K-mart and Target type stores have them in the
auto department too.  Once you see one, it will all be instantly clear.
They are very different from the older can type coils and such.  They hide
in the distributer caps so you easily may have never seen one.

	Terry
 
	Holder of the coveted GMHEICSLR :-))