RE: H/D ratio

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

Original poster: "Lau, Gary" <gary.lau-at-hp-dot-com> 

The choice of secondary size, wire size, top load size, aspect ratios, 
input power, and almost everything else is all interrelated and as with 
most things, is a trade off between several problems.  For one to ask for a 
concise answer to all of this is unrealistic.  Some aspects of these 
choices are only marginally understood, and to summarize all that is known 
about optimizing all design aspects, even if we could come to an agreement, 
would take more time and bandwidth than are available.

For the 900W 2" W x 9" L secondary - how long do you think the sparks will 
be coming off the top will be?  Most with similarly powered coils report at 
least 1-2 feet, often more.  I would suggest something longer than 9".

If you had a 50" diameter coil, what would be the total secondary 
capacitance?  The higher the Csec, the lower the peak secondary voltage 
would be.  And a large top load would require a higher breakout voltage, so 
it's unlikely you'd get breakout to occur.

There is no formula for choosing the optimal middle ground between these 
examples.  They both fail for different reasons.  The middle ground is 
obviously good because the extremes won't work.  The best one can to is try 
what has worked for someone else, and experiment further.  This is what 
makes this hobby so much fun - if this were an exact science, we'd all have 
identical coils.  Where's the fun of a race if everyone runs the same speed?

Choosing absurdly large and small wire diameters and numbers of turns will 
also lead to designs which won't work for a different set of 
reasons.  You're not going to learn all of this at once, so be patient and 
read the List archives - quite a lengthy task!  In the meantime, you're 
going to have to accept some advice at face value.

Regards, Gary Lau
MA, USA

=========================================================

Original poster: "Luke" <Bluu-at-cox-dot-net>

4.5:1 is good I get it.
So I can build my secondary 2" wide and 9" tall with an input of 900
watts.
Seems we have been here before.

If 2" coil is bad and 4 is better and 6 is better and 8 is even better
then a 50" dia coil would be incredible.

So maybe I should just go with a 50" diameter coil so my height would
work out to be 225".  I could set this up and fire off some long arcs in
my back yard powering it with 900 watts.

These are both extremes.
Where is the middle ground?
Ok here is where you give examples of coils that are in the 900watt
range and tell me the diameters and heights.
NO NO NO
Don't go there please.

I am looking for WHY the middle ground is good and HOW you or they have
figured out where that middle ground.

I re word this question in every way I can think of only to be greeted
with a well meaning response that tells me this works well.  I WANT TO
KNOW WHY!!

Luke Galyan
Bluu-at-cox-dot-net

-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Thursday, January 15, 2004 6:02 PM
To: tesla-at-pupman-dot-com
Subject: Re: H/D ratio

Original poster: "Dr. Resonance" <resonance-at-jvlnet-dot-com>


The optimum is 0.9.  A coil this short will have constant arcing
problems
top to primary and top to ground.  A 4.5:1 gets the toroid a distance
away
from the primary and allows an even potential buildup along the
elongated
sec coil.

Dr. Resonance

   >
   > I found on the net in a few places stating that the maximum amount of
   > inductance from a coil is when the height is the same as the
   > diameter.  This is a 1:1 ratio.
   >
   > If that is the best inductance ratio then why is this ratio not used
for
   > the tesla coil secondary to take advantage of a high inductance ratio
   > between the primary and secondary?
   >
   > Luke Galyan
   > Bluu-at-cox-dot-net
   >
   >
   >
   >