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APPROPRIATE CAP...?


 > From: Dan Kline <KLINEDA-at-UNIVSCVM.CSD.SCAROLINA.EDU>
 > Subject:      Appropriate Cap...?
 > To: Richard Quick <RICHARD.QUICK-at-SLUG.ST-LOUIS.MO.US>

 DK> Dear Richard,

 DK> I wanted to ask you this personally, so please excuse me for 
 DK> writing uninvited, ok? (I just didn't want to take up Tesla- 
 DK> list bandwidth with it) 

No problem with writing uninvited, and as for the bandwidth...
I thought that's what it's there for!

 DK> I don't have the best of memories, but it seems to me that   
 DK> back in '87, '88, or '89, someone named Richard Quick sent a 
 DK> letter to Popular Electronics or Radio Electronics with a    
 DK> picture of what he called "a medium-sized coil." There was a 
 DK> white band around the secondary that was "used for measure-  
 DK> ment purposes only", and the picture had been taken outside  
 DK> and the scenery looked western. If this was you, I think
 DK> that maybe you can give me some advice about whether or not  
 DK> I'm going to have to build a capacitor or not. 

I am sorry, it was not me. But I forwarded your post (and a copy
of this reply) into the group so that maybe someone will
recognize either the capacitor, or the article.

 DK> It seems that the capacitor-bank used on that coil was made  
 DK> up of exactly the same type of capacitor I want to use on my 
 DK> next coil. The kind I'm "speaking" of had heavy aluminum     
 DK> end-plates, the body is covered with brown kraft-type paper, 
 DK> the capacitance was .02 microF, and the voltage rating was   
 DK> 120 kV. I got it from Fair Radio Sales a few years ago. 
 DK> Does this ring a bell? 

No, not me. Anybody else?

 DK> Anyway, if you are familiar with that particular capacitor,  
 DK> can you tell me of the appropriateness of it's use for a     
 DK> Tesla-coil? Will it work ok? It has in the past, but only in 
 DK> the old-style configurations. I will be doing new style on   
 DK> this next coil, which is why I'm asking about this           
 DK> capacitor. Thanks for any info!

If the cap worked on your previous coil, and you were happy with
the performance, it will work quite well with the high inductance
secondary and large primary. I can always tell from the color of
the secondary spark if the capacitor in the tank circuit has high
enough Q. If the spark was thick, white, and violent, with little
or no violet or purple-blue color; it was pulsing well. Violet,
blue, purple, or reddish spark (or hues) tell me the cap is not
performing.

 DK> Also while I've got you here, :) I had a very small system   
 DK> that ran on 270 W, with glass cap bank, and cylindrical      
 DK> primary. The secondary was 3.5 inches dia. and 12 inches     
 DK> tall. I could get about a 7-8 inch spark out of it. Not too  
 DK> bad for a small system. Then I took your advice...

 DK> First, I pounded a 5 foot, copper pipe into the ground and   
 DK> connected it to the system with 6-gauge stranded wire,       
 DK> rubber covered.

That's what I call rebuilding from the "ground up"! Bravo!

 DK> I put 450 W into the system, made a toroid, added turns to   
 DK> the primary, retuned and fired it up. I was getting double   
 DK> forked sparks about 16 inches long! I was totally amazed     
 DK> right up until the secondary burned up! :) I had wound on    
 DK> PVC with only polyurethane top-coats, using 24-gauge wire.   
 DK> Also, the primary was only 8" in diameter. The next coil     
 DK> will incorporate your designs and should be fairly           
 DK> spectacular! You really know what you are talking about! 
 DK> Thanks! Dan <klineda-at-univscvm.csd.scarolina.edu>

Thank you for the very nice complement. Your basic data shows
that using just some of the more important points that I have
covered, your efficiencies have really improved: your spark
length exceeded the length of the secondary coil by 25% (16 inch
spark vs 12 inch long coil form); the secondary spark has more
current (split forks); the original setup required 33.75 watts
per inch of spark, but the reconfigured coil produced a hotter,
longer spark with only 28.2 watts per inch. Not bad for a small
coil! If the coil had been properly capped, with no holes drilled
and the wire never entering into the coil form, it would have
held up without breaking down or burning up. Sorry about the loss
of the coil, but it made a real show case for the design theory.

Richard Quick


... If all else fails... Throw another megavolt across it!
___ Blue Wave/QWK v2.12