Re: Tesla Coil Blunderbusses

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

Original poster: "Terry Fritz" <twftesla-at-uswest-dot-net>

Hi Malcolm,

At 09:01 AM 4/18/2001 +1200, you wrote:
>Hi John,
>
>> I wonder if just observing the gap by eye or with some sort of light
>> meter to gauge its brightness might be a quick test that folks could
>> use if they don't have a scope hook up.  The coil would be tuned for
>> it's best output at low power, then the power would be turned up and
>> the gap brightness observed.  Next, the coil would be re-tuned for
>> longest spark output, and the gap brightness would be observed to see
>> if it gets dimmer.  If it gets dimmer, this would suggest a faster
>> quenching, and would suggest that this outward tune point permits less
>> energy to return to the primary, either because of greater spark
>> loading, or for some other reason.  Often, a more inward tune point
>> gives more numerous, but shorter sparks.  I've noticed that numerous
>> sparks often gives better quenching than fewer longer sparks, so if
>> the quenching improves in the experiment, this would be significant. 
>> If the quenching gets worse, then it could mean that poorer quenching
>> is desireable up to a point as has been suggested by some in the past.
>
>Myself included. I pondered this apparent paradox over the break. We 
>*know* quench is largely dictated by secondary losses so I wonder if 
>such tuning would have any effect. Problem is, I'm still wondering 
>because I was unable to perform the test. My garage is totally 
>unsuitable for a variety of reasons so I simply must find time and 
>space to do it here at work. I hope we have an open day this year. I 
>would get a grand opportunity to test in the best possible 
>surroundings. I'd like to settle the question once and for all.

I designed my small coil taking the streamer loss as 1pF/ft in series with
220K ohms.  I also designed it so that with this load it would
automatically run out of energy on the first notch and "self quench".  As
it turns out, it all really did work just perfectly!  That 1pF/ft+220K
thing has never let me down.  I am sort of surprised such a simple estimate
for streamer load seems to be holding up so well.  In this case, getting a
good estimate of the streamer load was very improtant since it had a very
big effect on the time it would take for the secondary to ring down.  I am
still not sure it was worth all the time and effort to get it to do that,
but the design models ended up predicting the real coil's behaviour very well.

Cheers,

	Terry