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Re: Coil Form needed 2
Original poster: "Dr. Resonance" <resonance-at-jvlnet-dot-com>
Experimenters should use caution when trying to use large PVC pipe as a
coilform. We used PVC pipe coated with 3 coats Glyptal inside and outside
for our line of VDGRF generators. As soon as we crossed the 10 inch dia.
threshold the VDGRFs stopped operating properly (3 inch spark from a 40 inch
dia. terminal) even though the small 6 inch ID PVC pipes worked great up to
750 kV DC.
It seems above 850 kV DC the larger surface area (internal) of the PVC pipe
becomes more conductive and becomes unsuitable for VDGRFs. The leakage
current becomes too high so the terminal charge drains away faster than it
is accumulated.
Above 850 kV we use fiberglass (extren) pipe. We also use this material on
all TCs with dia. larger than 12 inches.
The PVC pipe works great for smaller than 12 inch coilforms but be sure to
seal it inside and outside with Glyptal before winding. Light sanding
inside and outside prior to coating is adviseable.
Dr. Resonance
>
> This might be worth mentioning. About 3 or 4 years ago I posted this
> information on the TC list so it may be in the archives someplace. It
has
> been so long ago I have forgotten all the details. I did an experiment to
> see if a large coil could be built using small diameter pvc pipe because
> large pipe is expensive and hard to find. I wound 3 identical secondary
> coils, connected them all in parallel in the center of one flat wound
> primary coil. I placed a toroid on top and fired it up. It worked
> excellent. Then I build one large diameter secondary coil to replace the
3
> parallel coils the fired it up again using the same primary coil, same
cap,
> same spark gap, same chokes, same transformer, same toroid, same size
> enamel coated copper wire. As I recall the output sparks were about the
> same on both experiments. I had planned to build 6 identical secondary
> coils and connect them all in parallel but never got around to doing that.
> If you are thinking about building a large coil and can not find any large
> pvc pipe give this experiment some thought.
>
> Gary Weaver
> gary350-at-earthlink-dot-net
> Why Wait? Move to EarthLink.
>
>
> > [Original Message]
> > From: Tesla list <tesla-at-pupman-dot-com>
> > To: <tesla-at-pupman-dot-com>
> > Date: 5/13/2004 3:23:35 PM
> > Subject: RE: Coil Form needed
> >
> > Original poster: "making lightning comcast"
<makinglightning-at-comcast-dot-net>
> >
> > I put 2x4's in the form of a cross on the inside of the ends, then
> drilled a
> > hole through the middle with a pipe going through the middle.
> > I use bungee cords sewed together that wrap around the tube and then
down
> to
> > a geared motor. I put a layer of friction tape on the end of the tube
for
> > the bungee cord to grip on.
> >
> >
> > -----Original Message-----
> > From: Tesla list [mailto:tesla-at-pupman-dot-com]
> > Sent: Thursday, May 13, 2004 10:02 AM
> > To: tesla-at-pupman-dot-com
> > Subject: RE: Coil Form needed
> >
> > Original poster: "Arpit Thomas" <arpit-at-inzo-dot-org>
> >
> > wow, thats not bad at all! I paid 20 dollars for one metre of 6 inch
pipe
> :/
> > So where do you get the end caps for them? I'm assuming you'll need end
> > caps so you can atach it to a winding machine. 6 inch end caps are
about
> 25
> > bucks each at the local hardware store- all the 6 inch fittings are
very
> > expensive.
> >
> > *********** REPLY SEPARATOR ***********
> >
> > On 12/05/2004 at 10:00 PM Tesla list wrote:
> >
> > >Original poster: "makinglightning comcast"
> <makinglightning-at-comcast-dot-net>
> > >
> > >Paul,
> > >
> > >I have been able to go to a construction site and just ask some guys
> there
> > >for a piece. Usually an 80 foot 12" is just scrap to them. I got 2
12"
> 15
> > >footers for a case of Bud once. I got a 12' 18" one for free also.
> Those
> > >are
> > >harder to come by, but the 12" ones are used all the time in new
> > >subdivisions and commercial buildings. They sure are building a lot
> > >nowadays, so it should be easy for just about anyone to do this.
> > >
> > >Kevin
> > >
> > >-----Original Message-----
> > >From: Tesla list [mailto:tesla-at-pupman-dot-com]
> > >Sent: Wednesday, May 12, 2004 6:03 PM
> > >To: tesla-at-pupman-dot-com
> > >Subject: Re: Coil Form needed
> > >
> > >Original poster: DRIEBEN-at-midsouth.rr-dot-com
> > >
> > >
> > >
> > >----- Original Message -----
> > >From: Tesla list <tesla-at-pupman-dot-com>
> > >Date: Wednesday, May 12, 2004 9:20 am
> > >Subject: Coil Form needed
> > >
> > > > Original poster: "Paul Marshall" <klugmann-at-hotmail-dot-com>
> > > >
> > > > I am looking for a coil form 12" or greater diameter. The length
> > > > should be
> > > > about 4 times the diameter. Also I am planning on using a 40kV
> > > > .5uF
> > > > capacitor for the tank circuit. I have a 25kVA pig to drive it.
> > > > Has anyone
> > > > on the list ever used that much capacitance in their tank
circuit ?
> > > >
> > > >
> > > >
> > > > Paul S. Marshall
> > >
> > >Paul,
> > >
> > >I would think that 0.5 uFD would be way too large for
> > >anything except maybe for an Electrum sized coil. The
> > >biggest cap that I've used so far is .0825 uFD, but I
> > >do now have (2) 0.1 uFD, 50 kV Hipotronics custom Tes-
> > >la caps that I got from Jeff Parrise of KVA Effects.
> > >I plan on using one of these for my future BIG coil
> > >project and driving it with a 15 kVA pig.
> > >
> > >As for large diametered secondary coil forms, I was
> > >able to get gray PVC ducting pipe from a local plas-
> > >tics supplier. I had picked 12" but they had 18" too.
> > >Of course it was quite pricey, though. I payed over $5
> > >a foot for the 12" and I'd hate to even ask how much
> > >the 18" was ;^0 Another cheaper alternative is the
> > >concrete former tubes. They are cardboard and are
> > >considered to not be the best form material due to
> > >higher lossiness and low Q, but if thuroughly dried
> > >and varnished, they do work. I know from experience.
> > >My biggest coil to date used a 12" dia cardboard
> > >"Quiktube" concrete fromer from Home Depot and it
> > >was only about 38.5" long but gave 8 to 10 ft. sparks
> > >from a 9x30 toroid and driven by a 10 kVA pig (14.4 kV)
> > >and with the aforementioned .0825 uFD primary capa-
> > >citance and a homemade lexan and brass RSG.
> > >I've seen 24" concrete formers at construction sites
> > >so you could definitely build a large coil with one
> > >of these.
> > >
> > >David Rieben
> >
>
>
>