Re: Mini OLTC is getting 9"

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

Original poster: "Stephen Conner by way of Terry Fritz <teslalist-at-qwest-dot-net>" <steve-at-scopeboy-dot-com>

At 18:46 15/03/03 -0700, you wrote:
>Original poster: "Terry Fritz" <teslalist-at-qwest-dot-net>
>
>Hi Steve,
>
>Wow cool!!
>
>Same hot mean sparks as mine.  Interesting that you have so much control 
>over BPS!  Does it make any difference??  With the OLTC being so highly 
>controlled otherwise, you should be able to tell if say 120 bps is any 
>better or worse than say 600 BPS...  That is a very old question that 
>maybe you can study!

Playing with the OLTC has been really interesting and I learnt a lot about 
spark length and so on. I basically found that bang energy is by far the 
most important thing. Big bangs at a low BPS seem most effective for 
building streamer length. For instance, If I turn the bang energy down by a 
factor of four, then turning up the BPS by a factor of four doesn't restore 
the lost spark length.

However, if the BPS is too low, then the discharge channel will have time 
to cool between bangs and you'll lose the streamer growth effect where the 
next bang grows out of the end of the previous one. On my OLTC the streamer 
growth starts at about 500bps when the bang energy is max. At lower bang 
energies it never starts at all: I just get a little VTTC-like brush discharge.

I found it interesting to compare with my conventional coil. It has a bang 
energy of 1.9 joules which produces an arc about 10" long at 1bps. At 
100bps this increases to 17" and at 500bps it's 30". Whereas the mini OLTC, 
with energy of around 0.43 joules, gives 5" at 2bps and 9" at 1200bps.

Also, you can compare with the 1.7 * sqrt (p) formula. It was meant for 
120bps systems, and suggests that my conventional coil would do 53" if it 
were still 1kW but ran at 120bps rather than 500.

My conclusion from all of the above is that high bang energy is doubly 
important, because it makes bigger sparks in the first place, and also 
responds better to upping of the BPS. So y'all keep saving those empty 
Corona bottles ;)



>Wonderful to know that there are now two!!  I bet you don't miss the big 
>transformers (not knowing how big your DC supply is).

The whole system is totally self contained and can be picked up in one 
hand. It's a success on that score.


>I do note that for a given power we seem to be getting about the same type 
>and length of streamers even though the frequency is 4X different.

I looked at the pic you sent and it does seem to be a similar thing. Is 
that the wall of your shop the coil is sparking to? Also, how did it work 
just forming streamers into the air? I'm wondering because I heard that a 
higher frequency would give better streamers, even though arcs would be no 
different. This was a very short burst of 1200bps on 340V filtered DC: The 
discharge looks quite halfwave SSTC-like.

http://www.scopeboy-dot-com/tesla/oltc1200streamer.jpg

Steve C.