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Re: [TCML] Racing sparks - question

Thanks everybody for your replies.  To answer a few questions you guys raised:  

JAVATC calculates the coupling coefficient at .122k, below the recommended .137
break rate is 206 bps
I have handled the secondary without gloves to get it in place, but later wiped it down with rubbing alchohol
the secondary 6.6" in diameter, winding length 29 7/8 inches of #26 AWG for 1650 turns

At this point unless I hear any other ideas, I'll just continue to play with the secondary height and separation between toroids and see if I can work it out.  

Thanks again, Dennis Hopkinton MA

-----Original Message-----
From: DC Cox <resonance@xxxxxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Sun, Aug 8, 2010 10:24 am
Subject: Re: [TCML] Racing sparks - question

If you have handled the sec without gloves on there is a strong possibility
hat sodium salts from your skin may have been deposited on the wires thus
ausing various conduction points along the coil.  Some people have very dry
kin so this may not be a problem, while some have more damp skin and there
s a lot of conductive sodium in your sweat.
If racing sparks have occured you now have very small "pinholes" in your
nsulation which can lead to continuing problems.  If only a few you might
et by, but if there are a lot of them, sometimes so small you can't even
ee them, or if they are on the inner side of the wire where you can't see
hem, then rewinding is the usual solution.
Best way to properly set coeff. of coupling is to use JAVATC to accurately
alculate the k value.  Keep it in the general range of 0.1 to 0.14.  I
sually find that 0.15 to 0.2 gives me the longest sparks.  You should also
se the "water heater element" method to measure the coeff. of coupling.
ou can also small a small elec. heater --- anything that gives you a
rimary current limit around 10 Amps will work fine.
All of these issues need to be properly addressed to eliminate this
roblem.  With most high voltage systems, in which great stress is always
resent, once sparking has occured it will continue.  You may even have to
ewind the sec coil is this problem continues to plague you.
Best regards,
Dr. Resonance

On Sat, Aug 7, 2010 at 7:43 PM, <otmaskin5@xxxxxxx> wrote:
 Hi coilers.  Life's been busy the last few months & not much time for
 coiling, although I still read the pupman postings.  Anyway, I did find the
 time to roll out my coil tonight & run it, but I kept running into on an old
 problem I've had in the past.  Using a screw or ball bearing for a breakout
 point, my 15/60 coil produces good sparks, and the coil runs well with no
 problems.  If I remove the breakout, I still get sparks from the toroiod,
 but eventualy start getting racing sparks.  Without the breakout point, the
 coil seems to have no trouble producing sparks from the topload even fairly
 lower variac voltages, but when I increase variac the voltage to the 120 or
 higher I eventually get the racing sparks.    I've played around with
 raising the secondary to reduce coupling, but so far, I'm still getting
 racing sparks if I dont use a breakout.

 If it's just a matter of over coupling, I'll have no problem gradually
 raising the secondary to eliminate the problem.  However this will be
 somewhat involved as I have to removing the secondary's end cap & adding a
 longer mounting bolt.  Before I go much further, I wanted to see if any of
 you guys had other suggestions on what might be causing the racing sparks
 when I don't use a breakout.  I'd really like to be able to run the coil
 without using a breakout.

 FYI, I have a 6 X 20.5 toroid and a 3 X 12 toroid underneath it.

 Thanks for any suggestions, Dennis Hopkinton MA

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