Re: Newbie questions. (fwd)

From: 	Bert Hickman[SMTP:bert.hickman-at-aquila-dot-com]
Reply To: 	bert.hickman-at-aquila-dot-com
Sent: 	Saturday, January 10, 1998 9:10 AM
To: 	Tesla List
Subject: 	Re: Newbie questions. (fwd)

Tesla List wrote:
> Date: Fri, 9 Jan 1998 20:39:15 -0700
> From: Tim Dempsey <tdempsey-at-easley-dot-net>
> To: Tesla List <tesla-at-pupman-dot-com>
> Subject: Newbie questions.
> Hi all,
> I have a few questions about constructing my first(real) coil, any help
> would be greatly
> appreciated.  I recently acquired some 5' pieces of 2.25'' O.D. pyrex
> pipe.  I am planning on winding my secondary around a bundle of 7 pipes,
> cut(if I can figure out how to cut this stuff) to a length of approx.
> 30''(28'' winding.)  Will it cause any problems if my form is not
> completely round?   Also, I am planning to wind the secondary using 26
> gauge magnetic wire, bifilar wound.  I wasn't sure whether it would act
> as two separate coils in parallel(Yuk) or decrease the resistance by
> acting as one conductor.  I wound a small bifilar coil (2'' dia x 1.5'')
> on a PVC form and measured the inductance of one coil and then with both
> coils in parallel.  The inductance didn't appear to change, is this
> correct or should I chuck my 26 for a spool of 20 gauge? And last but
> not least, a friend of mine has a roll of polyester film he obtained
> from a capacitor manufacturor,it is suppose to be able to withstand 10
> kV, but I haven't been able to find any information on it's dielectric
> constant or whether it's even good for pulse capacitors? Does anybody
> have any information on the properties of polyester?
> Thanks in advance,
> Tim Dempsey
> tdempsey-at-easley-dot-net


The resonator's shape doesn't matter matter very much as long as the
wires from loops that can interect the primary's field. However, it may
be considerably easier to wind a simple circular cylinder. It will
definately be much easier to wind a single wire layer rather that a
bifilar winding, especially on a non-circular form. Go with 20 or 22
Polyester film is polyethylene terephthalate (PET), or Mylar. It's a
great high breakdown voltage insulating film... for DC. Unfortunately
it's also very lossy in Tesla Coil service. It's relative dielectric
constant is 4.0, but it's loss tangent is a function of frequency, and
is around 2.0 x 10^-3 at 60 Hz, rising to 20.0 at 1 MHz. This is about
10 - 100 X lossier than Low Density Polyethylene (LDPE) or Polypropylene
Caps made from this material WILL work, but they'll heat up and won't
perform as well as those made from LDPE or PP. If your friend can get
some PP film, you'd be in business! If the PET film isn't metalized, you
may be able to use it for insulating purposes in other coiling areas -
between layers in transformer or choke windings, between the ferrite
core and windings, etc...

Safe coiling to you, Tim!

-- Bert --