Re: tesla coil hight? and Need 30 mil poly!

[Hollmike-at-aol-dot-com (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

In a message dated 7/28/2000 9:46:19 PM Mountain Daylight Time, 
tesla-at-pupman-dot-com writes:

Alex,  
    If I were designing this coil, I would go for a 6 by 30 secondary with 21 
to 22 g wire.   21g would give you about 990 turns(depending on the 
insulation thickness) and 22g would give you about 1110 turns.  This seems to 
be the range of turns that most coilers use with good results.  Either choice 
would work pretty well.  I would guess that 22g is easier to find.  I only 
picked 21g as an example because I have most of a 50lb roll of it and it was 
already on a spreadsheet for one design I did a while back.
    Next issue is the cap.  The most popular way to go these days is to use 
the series/parallel bank of polypropylene caps lovingly termed the MMC(or 
EMMC if you get fancy with it).   If you are dead set to build your own cap, 
I would suggest getting the poly from McMaster Carr(www.mcmaster-carr-dot-com).  
I ordered a 4ft by 8 ft sheet and a roll of aluminum roofing flashing that 
made for a nice cap.  An even better notion might be to write to the list 
owner, Chip and see if he has some of these materials left.  He just posted a 
letter to the list advertising some of these materials for sale.   Now that 
that is said, I took the liberty of choosing a cap value that would probably 
work fairly well(always some debate as the best choice in this).  This value 
is .015uF.  I chose this to be more than the impedance match in order to 
reduce(eliminate?) the tendency of creating a resonant condition with your 
NST secondary that could kill it quickly.  You could go up a lot higher( up 
to about 4 times the impedance match), but this seems like a reasonable 
starting point,.  If using 22g wire, you would want a primary of 
approximately 13 turns and your resonant frequency with a 6 by 22 topload 
would be about 140 kHz.   21g would raise that to almost 160kHz and your 
tuning of the primary would be something close to 11.7 turns(assuming 2 inch 
clearance to the secondary and 1/4 inch spacing jof 1/4 inch copper refrig 
tubing).
      I made the above calcs based on an actual 6 inch diameter form.  If you 
use regular pvc pipe, the only real difference would be the resonant 
frequency being lower and that you would need to increase the primary turns 
accordingly.  The 13 turns would be more like 14 in that case.  I would make 
the primary with a few extra turns, just for good measure.  
Hope all this helps a bit,
Mike




> Original poster: "Alex Madsen" <alexmadsen-at-netzero-dot-net> 
>  
>  Is there a general formula or something to determine the optimal height of
>  an Tesla Coil for its transformer.  I know that it is a good idea to keep a
>  1 to 5 high to diameter. What is the ideal wire gauge. My power supply will
>  by a 15kv 60 ma. I am thinking about a 4.5 x 22 or a 6 x 30. Secondary.
>  
>  Where can i get 30 mil poly for caps. The only place i found sold it for
>  pond lining but it was to big (50 by 5)
>  
>