Re: [TCML] My first Tesla coil

[drieben@xxxxxxxxxxx (David Rieben)]

Hi Rob,

I was just wondering how you managed to build a 
coil that was based on, no matter how "somewhat
loosely", a coil featured in a 1964 article in the 
EARLY 1960's? Maybe it's just a matter of se-
mantics but "I" would consider 1964 to be in the
MID 1960's. Otherwise, it's safe to say that you
built that coil over 40 years ago :^)

Also, I seriously doubt that those 25 kV rated 
WWII Navy surplus caps were truly electrolytics.
Electrolytics are strongly polarized and will only
work with DC and would almost instantly fail 
explosively in a Tesla tank circuit. About the highest 
voltage rating that I've ever heard of in a true electro-
lytic cap is 550 volts - not anything near 25 kV!
>From your description of them I would imagine that
they were in fact high voltage (PCB) oil-filled filter
capacitors, which are generally rated at DC voltage.
Assuming this is the true type of capactiors that you
had, the military surplus store owner was still correct
in telling you that they could explode, since filter grade
caps are often too lossy for rapid pulse discharge duty
and can quickly overheat  in Tesla duty.

--
David Rieben

-------------- Original message -------------- 
From: "stamsund" <stamsund@xxxxxxxxxxxxxx> 

> I built a Tesla coil back in the early sixties based somewhat loosely on a 1964 
> article in Popular Electronics. The secondary was a phenolic tube 5 ½ inches in 
> diameter and approximately 36 inches high, coiled with 24 gauge enameled wire. 
> The primary was wound with poorly insulated #10 wire. I used (4) WW2 surplus US 
> Navy electrolytic DC Capacitors loaded with PCB . They were 25KV cans 
> approximately 5"X14"wideX15'high and weighed at least 40 lbs each. I used a 
> crude spark gap fashioned from heavy copper wire. I set up the coil in a large 
> garage and when I powered it up it roared and sputtered and lit up all the 
> fluorescent light fixtures in the building. My friends were dumfounded at my 
> genius and referred to me as the neighborhood mad scientist. 
> 
> 
> 
> The man who owned the local military electronic surplus store, who sold me the 
> capacitors listened to my ramblings about the fantastic display and gave me dire 
> warnings about the possibility that the capacitors might explode from the way I 
> was using them. I then built a shielded cage from heavy plywood and acrylic 
> windows so I could observe the phenomenon with some degree of safety, not 
> realizing that had the capacitors exploded, the cage would most likely be 
> shattered and PCB laden shrapnel would be everywhere including imbedded in yours 
> truly. 
> 
> 
> 
> Fortunately, the primary coil shorted and caught fire and the experiment ended. 
> 
> I still have the secondary coil and the NST. "Unfortunately", the capacitors 
> have been recycled as hazardous waste. 
> 
> 
> 
> I'm now much older and wiser and much, much more cautious. I'm planning to 
> build another coil using scientific methods and advice from experts like those 
> on this board. But like that foolish youth many years ago I'm still fascinated 
> by Nicholas Tesla and his profound and prophetic genius. 
> 
> 
> 
> Rob Robertsen, KA7YAK 
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> Tesla@xxxxxxxxxxxxxx 
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