Re: Secondary size

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

Original poster: Finn Hammer <f-h-at-c.dk> 

Luke,

You probably have to accept, that these proportions were developed trough 
experiments, rather than by calculations.

But let me offer an explanation, still:

A teslacoil secondary system has inductance and capacitance. The inductance 
is residing in the coil alone, whereas the capacitance is compounded by the 
coil self capacitance, and the topload capacitance.
The charge that is on the topload is available for streamer formation, but 
the charge that is on the coil self capacitance is not, because it would 
have to travel trough the coil to get to the topload, and streamer, and 
this is a slow process.

Since we want long streamers, we want the majority of the total capacitance 
to be -topload capacitance_.

Since the coil self capacitance is increasing with coil diametre and 
length, and we need a certain length to keep the coil from arching end to 
end, it follows that to get a small capacitance, it is an advantage to use 
as small a diametre as possible.

We cannot go too low on diametre either, because if we did, it would take 
so many turns to create enough inductance, that the wire would have to be 
too thin to make it.

Along these lines, trough experiment, and probably also aestetic judgement: 
(does it look pleasing) the present coil has evolved.

I know Bill Wysoc introduced the toroid in the late seventies, the conical 
primary was abandoned within the last 3-4 years, and so on it goes.

I think it is good that you ask these questions, because it is a chance for 
all of us to think about just why the present coil looks like what it does.

And perhaps you yourself will gain enough interest to start experimenting, 
or perhaps solve the equation by calculation.

Cheers, Finn Hammer

Tesla list wrote:
>Original poster: "Luke" <Bluu-at-cox-dot-net>
>Ok so 2" would be a bad idea.
>4 6 8 or even 10 would be better.
>Why not go with a 24" dia coil?
>With a 15KV 60mA NST and a rotary spark gap I should be able to get some
>huge sparks from a secondary that gives even more performance because it
>is a 24" dia. right?
>Comon sense tells me this would be nuts.
>But the question is WHY?
>If 6 is better than 2 then 50 must be better than 6 right?
>Where do you stop on how large to make the dia?
>I have had the idea that the larger your dia the larger your top load
>would need to be to shadow the secondary.  This large top load would
>have a high capacitance so it would work against output because of the
>capacitance ratio.
>If the sec dia should be bigger, how much bigger? And WHY?
>Luke Galyan
>Bluu-at-cox-dot-net
>-----Original Message-----
>From: Tesla list [mailto:tesla-at-pupman-dot-com]
>Sent: Thursday, January 15, 2004 7:18 AM
>To: tesla-at-pupman-dot-com
>Subject: Re: Secondary size
>Original poster: "Dr. Resonance" <resonance-at-jvlnet-dot-com>
>
>At 60 mA you should not run a 2" dia. coilform.  Even 4" reduces
>performance.
>If you're running 60 mA you could use a 6 " ID, 8" ID, or 10 " ID
>coilform
>with much greater output.
>Your resonant cap value would be 10.6 nF (.0106 uF).  This is, of
>course, a
>value you really don't want to use or potential resonant rise could
>occur
>and blow your NST.
>If you are running a stationary sparkgap your correct value would be 1.6
>x
>resonant value, ie, 1.6 x 10.6 nF, or approx 17 nF (.017 uF).  This
>keeps it
>above the resonant range and keeps your NST safe.
>Now, if you opt to go for max power, then you run a synchro RSG.  Use
>the
>10" ID coilform.  Your multiplier then becomes 3.2 x resonant value, ie,
>approx 34 nF.  This sounds like a lot of capacitance but remember your
>NST
>is not trying to charge it 2-3 times per 1/2 cycle, only once.  Sparks
>at
>4.25 ft with this setup.
>Dr. Resonance
>Resonance Research Corporation
>E11870 Shadylane Rd.
>Baraboo   WI   53913
>  >  > I know 4.5:1 works very well.  Since this is true I could then use
>my
>  >  > 15KV 60Ma NST, give it a SRSG and a MC of .028 micro farads.  Then
>my
>  >  > optimal coil height would be 9" tall right?  Providing I use a
>secondary
>  >  > dia. of 2" I would still be in the 4.5:1 ratio and poof I should
>fall
>  >  > into a good rule of thumb for my coil height.  I got it!  Thanx!
>  >  >
>  >  > Ok that was not meant to be sarcastic.  I was trying to show you
>that
>  >  > the ratio was not my question as stated in the original question.
>There
>  >  > were actually a few questions I had.  but in reference to the one
msnip........