[Prev][Next][Index][Thread]

Re: Gap Dwell Times (formerly: Beating Solved)

At 10:25 PM 10/15/96 -0600, you wrote:
>>From nikki-at-fastlane-dot-netTue Oct 15 22:05:48 1996
>Date: Mon, 14 Oct 1996 22:18:00 -0500 (CDT)
>From: Bert Pool <nikki-at-fastlane-dot-net>
>To: tesla-at-pupman-dot-com
>Subject: Re: Gap Dwell Times (formerly: Beating Solved)
>
>At 02:25 PM 10/12/96 -0600, you wrote:
>>>From ed-at-alumni.caltech.eduSat Oct 12 13:12:26 1996
>>Date: Fri, 11 Oct 1996 18:13:29 -0700 (PDT)
>>From: "Edward V. Phillips" <ed-at-alumni.caltech.edu>
>>To: tesla-at-pupman-dot-com
>>Subject: Re: Gap Dwell Times (formerly: Beating Solved)
>>
>>Re: Oil immersed coils.
>>	Has anyone in this group experimented with same, and if
>>so, what were the results.  There certainly is precedent, going
>>back to Mr. T himself.  Would be very much interested in any reports.
>>How about the Richard's???
>>Ed Phillips
>>
>>
>
>I am building and debugging a small but massive primary/secondary magnifier
>system right now which has both primary and secondary immersed in oil.
>Since this list is "conventional coil" oriented, I would be glad to discuss
>the specifics using direct E-mail if you are interested.
>
>Bert Pool
>nikki-at-fastlane-dot-net
>  
>[ Magnifier discussion is definitely ON TOPIC!  -- Chip ]
>
>

Since I have Chip's ok, here are some specifics:

I'm building this magnifier driver around a coil which came out of a very
hefty commercial transformer of some kind.  The coil is about 4.5 inches in
diameter, 18 inches long, and is wound with FLAT enameled wire that appears
to be between 6 and 8 gauge.  The wire is wound on _edge_, allowing many
turns per inch, as compared to conventional round wire.  Because of the
rather high inductance and large gauge of the wire, the current capabilities
of this coil should be excellent.  Since a magnifier driver's secondary has
to supply a relatively low voltage at very high current, I just had to try
this coil!

The coil fits snugly in a six inch diameter PVC pipe.  I decided to put the
coil in the pipe, fill it with oil and seal it up.  Next, I space wound 50
feet of 3/8 inch copper tubing on the outside of the PVC pipe, leaving a 10
inch space between the top of this primary and the discharge electrode on
the top.  When I fired it up, I immediately had a very hot arc burn a carbon
track from the secondary output down the side of the PVC to the primary.
The coil was definitely putting out, but this initial trial showed me that
both primary and secondary need to be in oil.  I tore it down.  I built a
large oil tank out of 12 inch diameter PVC pipe, 24 inches tall.  Because
the original primary was attached to the 6 inch PVC with hot glue, and was
now going to be in oil, I had to build a new primary (oil eats up hot glue).
Instead of a copper tube primary, I wound 21 feet of 3.25 inch wide copper
strap around the 6 inch PVC pipe.  This primary is now a flat spiral copper
band primary with 20 mil poly between the turns.  It is tapped every 24
inches.  Upon immersing the primary and secondary in oil, I tried again.
The oil did prevent any arc from the secondary discharge electrode to the
primary.  BUT I did have a direct arc through the oil and the wall of the 6
inch PVC pipe!

I have just torn it down again.  I am going to place several dozen layers of
good mylar insulation between primary and secondary (along with a new 6 inch
PVC pipe) as additional insulation, and I will retest later this week.

It looks like the oil is really helping, but because I am putting the
primary very close to the secondary for high coupling, primary/secondary
insulation is critical.  Mylar is very poor in capacitors as a dielectric,
but it works very well as a HV insulation.  I'll post updates on how all
this works.  

Oh yes, one other rather unique thing about the construction of this driver
which can apply to conventional coils:  I have a very, very good ground.  I
needed a very heavy ground connection which I could seal through the side
wall of my 12 inch PVC oil tank, one which could carry a lot of current and
seal against oil leakage.  I have installed a standard brass water faucet
(used as a replacement for most outdoor water faucets for gargen hoses)
through the wall of the tank, and have attached the bottom of my secondary
to the inside of the faucet.  Now comes the neat part!  I bought two brass
water hose fittings which screw onto the faucet.  I soldered 25 feet of
copper tubing to each screw-on hose connector; the copper line replaces the
garden hose.  One end screws onto my driver's "faucet", the other end of the
copper line screws onto the outside water faucet just outside the garage.
This real water faucet has a copper line going into the foundation of my
house.  Tracing it out, I found that I have a pure copper line buried all
the way out to the water mains, a distance of over 50 feet.  I doubt that I
could achieve any better ground, unless I could somehow get to that
battleship mentioned in earlier posts!  The faucet/screw-on connectors
worked so well for my ground connection that I made my my primary
connections the same way, they are also now attached through two more brass
faucets installed thru the walls of the oil tank!  Hey guys, you might want
to consider brass water faucets and brass water hose screw-on fittings for
your primary/tank connections: they are cheap, handle very high currents,
and the screw-on connections are very convenient.

Bert Pool
nikki-at-fastlane-dot-net