Re: Racing arc clues...

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

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

In a message dated 6/2/01 12:46:07 PM Eastern Daylight Time, tesla-at-pupman-dot-com 
writes:

> If you want to look, go to
>  
>   http://www.geocities-dot-com/rcopini/

Robin,

That's very impressive workmanship on the coil and gap!  More below.
>  
>  I run my coil about 1 time per month, or more depending on spectators. My
>  experience
>  is high heat levels definitely have a deleterious effect as far as racing
>  arcs are concerned. 

That is very interesting about the high heat levels.  The air would
thin out some at a high temp, I don't know if that may have some 
effect.  It is interesting that since your toroid has a rather large ROC,
and since you're running at a high bps, the spark probably doesn't
breakout until a high variac setting?  If that is the case, if under
certain conditions, the breakout is delayed, this would stress the
secondary more.  It would be interesting to lay a metal rod over
the toroid as a breakout point whenever racing sparks appear, to
let the sparks break out more easily to see if this stops the racing
sparks.

>  In good conditions, and at full power the coil has produced arcs
>  in excess
>  of 4.5 metres. In bad conditions, I can't power up to more than half input
>  power without having racing arcs. 

Then you can forget about my comments about the line voltage.
I doubt it would have that large an effect.

> I would be almost certain it has nothing to do
>  with my
>  cap, The longest run at high power levels, (within 10% of full power), was
>  for almost
>  7 minutes, (we were trying to destroy a laptop :-)  ), the coil never
>  altered it's
>  performance levels so a cap variation is fairly remote. I find this problem
>  very
>  interesting because the coil itself is never changed, just the running
>  conditions, so there, I believe, lies the root of the problem.

I agree the caps do not seem like the problem.   I wonder if on hot
days, the quenching of the gap may be affected.  I think poor 
quenching can sometimes promote racing sparks, I can't think
of why at the moment.  It would be interesting to direct some sort
of air blast at the gap during racing spark times to see if it helps.
Maybe delayed quenching can sometimes upset the cap charging
modes, and cause a firing to be missed, resulting in a larger
bang size the next time around.  This should cause the safety
gap to fire too.

I agree that the operating conditions seem to be the culprit.  On
bad days when racing sparks occur, do they begin as soon as
the coil is run up?  Or do they take 15 seconds or so to appear?

Still tossing around ideas     :)

Cheers,
John Freau

>  
>  Best Regards
>  
>   Robin Copini
>  
>  P.S. Chris, tell CD the caps are great!
>