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RE: text of july 1964 popular electronics article on tesla coils (fw d) (fwd)



---------- Forwarded message ----------
Date: Sun, 2 Mar 97 19:06:04 UT
From: William Noble <William_B_Noble-at-msn-dot-com>
To: Tesla List <mod1-at-pupman-dot-com>
Subject: RE: text of july 1964 popular electronics article on tesla  coils (fw d)

What bugs me about this isn't that the coil didn't work - I think I understand 
the tuning part now, what bugs me is that the cover of the magazine has a 
photograph of the coil working.  So, it seems to me that I ought to be able to 
duplicate that, even if it's a crummy design.  - I'm using a commercial 
capacitor, not a plate of glass, maybe that has something to do with it.   I 
did try the following experiments:

1. added a metal toilet float to the top - small increase in arc, maybe - hard 
to tell
2. wrapped primary around a vinyl sheet rolled into an 8" diameter tube, and 
spread the windings out to about 1/2 inches apart.  no change.
3. tapped the primary (I wound 30 turns total) at turns 20, 15.  Small 
improvement at turn 20, 15 about the same.  much better if I ran 1o turns - 
e.g. turn 30 to turn 20.  about the same at 5 turns (e.g. 15 to 20).  At the 
smaller turns on the primary configuration, the secondary would arc through 
the vinly (.30, two layers) to the primary from about the midpoint of the 
secondary.  These arc were longer than I could draw off the top. This confirms 
to me that the coil is about twice as long as it ought to be.
3. messed around with the length of the spark gap.  no effect - either it 
worked or it didn't - tuning the arc was ineffective.

I haven't tried giving the secondary a good ground - per my prev post, the 
schematic has pri low side and sec low side tied together, so given that the 
CT of the sign Xformer is also grounded, this is impossible.  I will try 
isolating pri and sec and grounding Sec low side to Xformer case and see what 
happens.

I think I may also try making a plate glass capacitor exactly like the article 
- that (it says it's .00027) is about triple what my capacitor seems to be 
labeled.  Maybe I'll also meaure my capacitor and see what it's value is - 
since the label is corroded, I could have misread it.

(and, yes, I'll make a half length secondary soon, but first, there is this 
small matter of a trip to abu dhabi...)

-----Original Message-----
From:	Tesla List 
Sent:	Saturday, March 01, 1997 3:21 PM
To:	tesla-at-pupman-dot-com
Subject:	Re: text of july 1964 popular electronics article on tesla  coils 
(fwd)



---------- Forwarded message ----------
Date: Sat, 1 Mar 1997 18:30:03 +0000
From: "John H. Couture" <couturejh-at-worldnet.att-dot-net>
To: Tesla List <mod1-at-pupman-dot-com>
Subject: Re: text of july 1964 popular electronics article on tesla  coils 
(fwd)


William -

It is unfortunate that you have gone to so much trouble to perpetuate the
plans for a Tesla coil that does not work. Dozens of these coils have been
built in the past and all of the builders I have talked to said the coil did
not work without making extensive modifications. I know of one museum that
has this coil on display but not working at the time. It was obvious that it
had been greatly modified with many attempts to make it work.

The reason this coil does not work is simple, the primary circuit is not in
tune with the secondary circuit. A few simple calculations will reveal this
problem. In fact if you can do these calculations you have a very good start
with Tesla coil engineering. Several coilers have spreadsheet calcs that
makes the job easy.

There is one questionable advantage to building this coil. All of the
builders I talked to said they learned more about Tesla coils by building a
coil that did not work than by building one that worked the first time.

John H. Couture

PS - The JHCTES computer program will show you why this coil does not work
and will also show you what to do to make it work. JHC