Re: Coil just won't fire...

Subject:  Re: Coil just won't fire...
   Date:  Wed, 16 Apr 1997 17:00:10 -0500
   From:  Chuck Curran <ccurran-at-execpc-dot-com>
     To:  Tesla List <tesla-at-pupman-dot-com>

> >       Mike...my partner and I have met with a problem. We have built >>a coil(description to follow) that just won't fire.We can tease a few >>6 inch arcs from it using a grounded rod, but it will not fire in free
> >air. Before I go on, I'll decribe this tiresome albatross to you.
> >
> >       Secondary
> >        The total winding lenth of this 3 1/2" coil using #26 copper > >wire is 17 1/4 ".The length of the PVC pipe is about 22 3/4"  >long,leaving about 2 1/2" at the top as a header and 3 1/8" at the   >>bottom (the top and bottom numbers represent pipe with no windings).
> >The ends of the pipe are sealed with plexiglass and the top has a   >1/4-20 X 1/2" bolt sticking out the top as a means to secure a   >>torid.The copper wire from the winding is terminated at this bolt.
> >
> >       Capacitors
> >The capacitors we are using are 6 long necked beer bottles filled with
> >sea salt and motor oil.The total capacitance of these bottles is about
> >.0043 uF.We did have one of these capacitors fail while trying  our
> >first coil (too large a spark gap) but these seem to be alright now.
> >
> >       Primary
> >Our primary coil is made from .375" copper tube wound in conical form
> >with.375" spacing.The form and spacing is maintained with a wooden and
> >plexiglass form.In total there are just over 15 turns on this coil
> >
> >       Transformer
> >Our transformer is a 9KV 120 mA neon .
> >
> >       Spark Gap.
> >The spark gap is made from 2 pieces of 3 1/2" X 3" X 1/16" copper plate
> >set up over a quenching fan and set at between .020" - .030".
> >
> >       Torid
> >We have 2 torids that we tried.One was  20"X4" made from Aluminum dryer
> >duct held together with pizza pie plates and Aluminum tape.The other was
> >about 8"X 2 1/2" styrofoam covered in aluminum tape.
> >
> >We have built a control pack that engages/disengages the capacitors and
> >bleeding resistors. This control also houses the autotransformer that we
> >use to control the primary voltage to our neon transformer.
> >When we attempt to fire this coil there appears to be nothing
> >wrong. There are no stray arcs,there is no overheating anywhere in the
> >ciruit. When we turn up the autotransformer to produce 180 Volts at the
> >neon primary we are drawing around 20 + amps (we did trip a breaker
> >while setting our spark gap ). We have plenty of arcing at the spark gaps
> >(the safety gap does not fire) We allowed this coil to try for about 10
> >minutes in total without any physical failure (ie we could still draw 6
> >inch sparks from the torid when we finally gave up). We even tried to use
> >an old secondary that we have laying around...It did not do any
> >better. We were able to get the 6" arcs by tuning the primary out to it's
> >maximum setting of 15 + turns. We were drawing 20 + amps and the power
> >was not  being consumed by over heating and/or sparks, so we were
> >wondering, could this be a coupling problem? If anyone has a suggestion
> >or idea we would very much appreciate the help.
> >
> >                                       Two VERY distraught coilers
> >
> >

Tim & Mike:
        After reviewing your coil description it sounds like a real good
start.  However, I would suggest that you get the plans for a new spark
gap from the Tesla ftp site.  One .020-.030 gap is probably not
quenching.  Go drive to any area where new road/sewer construction is in
progress and keep your eye open for a junk pile.  Sooner or later you
should see some 8" diameter PVC pipe scraps that you can use to build a
improved gap in--at least a 8" long chunk is needed.  Wash off the mud
and start building.  The alternative is to go out and stimulate the 
Economy by buying a 10' length.  The "Richard Quick" style gap would
really be perfect for your system and can be found at: 


I'll bet you a new set of beer bootles that you will notice a real
change with a better gap!  Good Luck with your project.

Chuck Curran