Re: secondaries

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

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Tesla729-at-cs-dot-com>

In a message dated 10/8/01 9:44:49 PM Central Daylight Time, tesla-at-pupman-dot-com
writes: 


>
> David, 
>
> Thanks for your nice comments about my coil work. 
> I agree it's good to have a high inductance to help reduce gap 
> losses.  I've calculated the inductance of your 12" x 38.5" 
> secondary with 660 turns of 16awg wire at about 35mH, with 
> about 18pF of Cself.  My proposed secondary 10" x 65" wound 
> with 1500 turns of 18awg wire has about 80mH, or more than 
> twice as much inductance, but just slightly more Cself at 23pF.   
> Using a 65" tall secondary, much, much longer sparks can be 
> obtained due to the greater voltage capability, and reduced 
> likelihood of the sparks striking the primary.  Using a 65" tall 
> secondary, it should be possible to obtain 22 foot sparks. 
>
> I still can't see why large coils would benefit from a different 
> aspect ratio than smaller coils, and I kind of doubt that they do. 
> It would be interesting to see a comparison test



John, 

You definitely raise some interesting points and you're 
obviously able to do much more extensive research in- 
to this phenomenon than I, hence you're observations 
would definitely be more authoritative than mine. I sup- 
pose that like Greg, I'm still kind of stuck in the old 
school of thinking along these lines. 

<<  Of course a 
<<short coil is good if you have limited available space. 

Bingo! There is the plight that I am stuck in. I am forced 
to operate my coil inside a 12X20 ft shop building with 
standard 8 ft ceiling rafters. And it's made of wood, a 
real fire hazard for throwing white-hot 8 to 10 ft. sparks 
in! I'd love to upgrade to 22 ft. sparks since a 10 kVA 
pole pig could provide the required power for it! I'm just 
too space constrained right now and I live in a farily ur- 
ban environment so outdoor firing of a giant coil is pretty 
much out of the question for now. 

<John 

David Rieben 

PS: I've already splintered one of the ceiling joist 2X4s 
with the white hot sparks form my coil to the point that 
it's weakened to the point that it's like it's rotted or ter- 
mite damaged :-(