Re: A Little more than general questions

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Peter Lawrence by way of Terry Fritz <twftesla-at-uswest-dot-net>" <Peter.Lawrence-at-Sun-dot-com>

Wade,
     I've been using a variety of wire sizes on the same size coil form of
3.5" diam by 12" high, everything from 495 turns of #24 wire to 1991 turns
of #36 wire. The following observations concern that size coil, YMMV:

I notice a slight improvement with the smaller wire and higher number of
turns, but it is pretty subtle.

that wire resistance matters is a total myth (at least for coils in this
size range).

The number one thing that affects performance is primary cap size, use the
"resonance" sized cap to 1-1/2 times resonance sized cap
Resonance nF = 2.652 * NST mA / kV  (eg  2.652 * 30ma / 12kv = 6.63nF)
for 60Hz transformers.

I would expect the number two thing to affect performance to be the torriod
size, but with my small coil, going from 2x8" to 3x12" did not really
change anything (8" diam torroid is 3/4 of my coil _height_ (not its diam))...

The number two thing that affects performance is the spark gap, I've switched
to tungsten-carbide, it does not foul up with corrosion and does not require
cleaning. It should be adjustable while running, and you have to have a
safety gap to let you know when you've openned it up too far or you will
burn out your NST.

go with a flat primary, anything else and you'll be over-coupled to the
secondary and get too many cross-winding sparks on your secondary and 
possibly burn through some wires (I have).

The primary spiral inductance falls out of the equations once you have selected
your primary cap and your secondary. Mine are all about 100-th of the number
of turns in my secondary, but that is mostly coincidence as there are an
infinite number of primaries with a given inductance each with a different
geometry. (my primaries all have an outer diameter of 11-1/2", and vary from
#2 wire (.25") at 2-TPI  to  #14 wire (.064") at 8-TPI).

enjoy,
-Peter Lawrence.


>Hi folks,
>  I am going to turn my questions to the primary and secondary windings.
>
>By increasing the diameter of the secondary coil, I will increase wire
>resistance, that is a gimme. In what ways does that affect the coil
>operation???
>
>Why is 1,000 turns of wire the magic # for this coil??? Of course if the
>turns are increased or decreased the inductance is affected, as would be
>the inductive reactance, as is it's ability to establish a magnetic
>field.
>And of course the secondary voltage is directly related to the # of turns
>in relation to the primary.
>
>My question is, what effects ( to the operation of the coil) would result
>if the turns are say.... doubled, or halved???
>
>On the primary coil how many turns would you all recommend??? Maybe a
>ratio to the secondary??? 
>And at what spacing???
>
>>From what I can gather from previous responses, it sounds like that a
>flat or coned primary is just a matter of preference??? Is there a
>different affect if the primary windings actually surround the secondary,
>other than the fact that one may risk damaging the primary with secondary
>strikes.
>
>Thanks, all of your comments are very helpful;
>
>Wade
>
>
>