Re: stepped leaders (was Safety FAQ...)

>>From leyh-at-ix-dot-netcom-dot-comTue Aug 20 22:10:15 1996
>Date: Tue, 20 Aug 1996 00:44:44 +0000
>From: "G.E. Leyh" <leyh-at-ix-dot-netcom-dot-com>
>To: tesla-at-pupman-dot-com
>Subject: Re: stepped leaders (was Safety FAQ...)

>Robert Stephens wrote:

>> I don't believe that phenomenon occuring on the enormous scale of stepped
>> leaders in natural lightning are necessarily useful in the explanation of
>> phenomena observed in Tesla coil  discharges.
> The smallest stepped leaders in naturally occuring ligthning are at a minimum,
>> at least an order of magnitude larger in scale than the biggest Tesla coil sparks
>> yet produced. The features of a Tesla coil streamer advancing upon itself in
>> small steps is absolutely microscopic compared to the stepped leader lightning
>> example referred to here by Greg.   Sorry folks,  I don't buy a small scale stepped
>> leader connection here for Tesla coils as based on the natural lightning example.

>The stepped leaders in a lightning strike will of course be much larger than the 
>stepped leaders generated by a tesla coil, since the voltages involved in lightning
>production are much higher.  Total cloud-to-ground voltages range from tens to hundreds
>of megavolts, which would yield leaders on the order of tens to hundreds of meters.
>My coil generates about 550kV, which should produce leaders of only a couple of feet.

>Perhaps some empirical data can solve this matter.  Anyone out there have a streak
>camera, or a 'Boys Camera', as they used to call it?



Malcolm was kind enough to recently send me a copy of your paper 
describing your big coil as published in the TCBA newsletter.  First 
off, nicely done! That project was an enormous undertaking, and will 
be useful as a reference to anyone such as myself with an interest in 
building a large Tesla coil system. 

I can't seem to locate where I misplaced your paper to in order to 
refresh myself, but I'm mentally recalling the dimensions and method 
of construction of the toploading toroid as being very close, in fact just 
slightly smaller to the one I put on my largest coil to date.  Mine 
was 15"X67", made from a custom manufactured single 33 foot length of 
aluminum flex duct, compressed as far as it would go to incresase the 
wall strength.  The fact that yours was made from individual discrete 
tubes, arranged to simulate a solid electrostatic surface by phantom 
effect confuses the calculation for breakaway potential to me as I am not 
personally familiar with that aspect of skeletal frame corona holdoff 

My point is, did you actually measure the terminal voltage achieved, 
or are you relying on a calculation by whatever CAD program you use.  
The charts supplied in your paper appeared to be CAD program generated 
rather than the output of a plotter hooked to a measuring voltmeter.  

My gut feeling tells me that the holdoff potential of your toroid, 
even being a skeletal design, ought to be significantly higher than 550 kilovolts!

I am aware of the difficulties involved in measuring such voltages 
with any degree of assurance, and am presently attempting to build a 
capacitive divider probe which will be capable of direct connection 
to the TC toroid and operate up to 1 megavolt for use in my lab.  

For now my guestimates of breakaway voltage from large holdoff terminals are 
based on measuring the length of the very first streamer to be caught 
breaking away from the toroid as seen stepping through a  videotaped 
record of the test.  On my largest system to date with the aforementioned toroid,
the system went from no corona whatsoever to a 12 foot streamer in the first 
ionization of virgin air.  At 20,000 volts per inch (which is a low 
number, 35KV per inch is probably more realistic), that represents 
2.88 Megavolts.  From 12 feet the streamer was then able to build, reaching a 
maximum recorded length of 18 feet at one point during the test of 
this coil.

Comments appreciated.
Regards, rwstephens