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

General comments on secondary prepping

Hi all,

I tried posting this this morning put it appears to have not made it so if
it does come up twice sorry...

    I just wanted to describe what I did as far as prepping/winding my
secondary coil for others who might be contemplating related questions.  I
am by no means an expert but the results were very good.
    First a little description of my coil and performance.  I am using a
stock (no shunts removed) 15/30 transco NST.  I am running it with straight
120vac (not through a variac).  Last night in the middle of a rain storm
(high humidity), in my basement, I was getting some 36 1/2" sparks to ground
off a small point on my toroid.  So that's 36 1/2" using 450VA.  I am rather
pleased (thanks John Freau for your recomendations...).  I am running 120bps
SRSG with an MMC of seacor KP25 .047ufd 1600vdc caps for a total value
around .0137ufd, 22,500vdc (4 strings of 14).  My coil is 22.5" of #28
double formvar magnet wire wound on schedule 40, 4" PVC (which is actually
4.5" in diameter.  It has 1,550 turns and uses about 2,200 feet of wire.
Two toroids are used the lower is 4.5" x 1.5" and the upper is 9" x 4".
Both are nicely polished.  The secondary is 1/4" copper tubing spaced 1/4"
between windings.  Inside diameter is 8 1/2" and it is tapped at 14.75
turns.  I am also using a modified version of Terrys' NST protection filter.
  The only difference with mine is that I am running it without the MOV's.
If I recall correctly Terry said it will eat about 5% or 10% of the NST
power.  I don't think the mov's eat much if any, but the 2 1k 100 watt
resistors eat some.  So without this circuit in place I might get 38" to 40"
    Ok, now on to my secondary prep work.  First I wet sanded the form using
400 wet and dry.  I did this until I saw no more writing and most of the
little nics and fabrication ridges where gone.  I placed it onto my homemade
winder which is motor powered and spins the form around 22 RPM.  I wiped the
coil down with a paper towel and some rubbing alchohol.  Then I secured the
wire to the coil with a piece of masking tape.  No, I did not pre-seal the
inside or outside with anything.  I also did not heat the form to dry it out
any.  I made this coil at least 1 month ago and as stated above just got
some 36 1/2" with 450va input.  BTW the first 1" or so is a pain but goes
smoothly after that.  Anyhow, I wound the entire length by running the wire
through a rag held in one hand that was soaked with either lacquer thinner
or denatured alcohol I forgot which but I think it was the lacquer thinner.
I was able to keep a good constant tension on the wire and cleaned off any
impurites in the process.  I used the nail of my thumb on my other hand to
keep pressure on the wire at the point of contact with the coil form to keep
the windings together nice and tight.  It is absolutely flawless with no
overlaps and not a hair of a space to be seen between any windings.  The
whole winding process took my about 1 hour and 45 minutes.  I did stop a few
times for a brief rest.  I then gave it a coat of spar (a marine)
polyuerathane varnish.  Then after 24 hours I ligthly wet sanded it with 400
wet and dry.  Cleaned it with a damp cloth then used a tack cloth after it
air dried to remove any dust particles.  I did this for 5 consecutive
nights.  You can look right through the form.  It was not vacumn sealed or
anything like that.  I don't know if pre-heating or sealing it would give me
any improvement in spark length.  Also the form is 1/4" thick walled PVC.  I
am curious if a different material or thickness would give me any
improvement.  Maybe I'll get ambitious one day but that won't be anytime
I'm too busy enjoying the fruits of my 3 months of labor.  Anyhow, I can't
with the choice of form material or size since my output is rather bitchen
if i offended anyone!).  BTW I tried adjusting the height of the coil so
that the
lowest winding was anywhere from 2" below to 2" above the primary winding
is a flat pancake winding).  I appears to work best right at or just above
primary winding.  At no point during tuning or running have I seen any
racing arcs.
One night I did get some arcs to the innermost primary winding but the coil
was not tuned right.  I hope this answers some questions some people might
have about how they might prep there coil.  Or how well a system might work
with John
Freaus' recomended ~1500 turn small diameter wire, low/medium powered

Safe coiling to everyone!!!
John M.