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Re: Modular Secondary



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

Hi Duncan,

I think the Skeldon paper is one of the better papers out there.  They did a
few things wrong but they also did many things right.  The paper is also fairly
easy to read.

Of course, I and many others may be able to argue a few points :-)) but they
did a pretty good job in general.  They also managed to get it all written up
very well and published which is often much harder than making the coil :-)

What is really fun is to realize that Tesla coils are far better understood and
known here in the "amateur" community rather than the scientific and industrial
communities.  That's not easy to do!!  I noticed they seemed fairly bewildered
at all the Internet information (early 1999).  The chart on the second page was
a good attempt at trying to put it all together but they never quite saw the
"holy grail" :-))  They should have just used John Couture's program. ;-) I
wonder how many man years have been spent by person after person re-deriving
the equation on page 128...  A lot of their information was just a repeat of
the web information they found so I guess we can't blame them for being led a
little astray by some of the "common knowledge" in the old year of 1999.  We
know much more now in modern times :-))

To their credit, a lot of recent information was not available when they were
doing this work.  I don't think any of these people were on this list at the
time.  However, they seemed to have learned a great deal in a short time.  They
seemed to have worked fairly independently.  I guess I was really interested in
their "clean room" view of coiling without being "contaminated" by us :-))

The output is really proportional to the 'square root' of input power, so I
have to take a few points off for that.  I am a little surprised they didn't
have a sync gap but at that time LTR and other ideas really hadn't caught on
and sync gaps were rather rare in general.  The "risk evaluation and skin
effect" is really weak...  The Faraday cage thing seems to forget the faraday
cages only shield against electrostatic effects and not high frequency magnetic
effects, but I guess they didn't bust their watch ;-)

I was a bit surprised that when I went looking for other information on the
group, the search engines pointed to my site were I have their paper buried
:-))
hot-streamer-dot-com/TeslaCoils/OtherPapers/Skeldon/ej0202.pdf
When the IOP was giving their papers away free to advertise their website, I
hear a few people wildly leached it :-)))

The paper is not exactly an infallible source of TC info, but they did a pretty
good job with what they had.  We must remember that many of the "experts" were
working with coils since before these people were born...  What is really great
is that they appeared to have learned a great deal and had a ton of fun with
their project!!  

Cheers,
        Terry


At 12:32 AM 3/11/2001 +0000, you wrote:
>Bonsoir Monsieur Luc!
>
>>Original poster: "Luc by way of Terry Fritz <twftesla-at-uswest-dot-net>"
><ludev-at-videotron.ca>
>>
>>Hi all
>>
>>I put this paper on the web at tis address :
>> http://pages.infinit-dot-net/luc2/colapsed_coil.pdf
>>It will be there for 2 weeks.
>>Enjoye it !
>
>
>Merci beaucoup, vous etes tres gentil!  And that's about all the
>French I remember, after two years in northern Belgium I can do better
>these days in Flemish ;-)
>
>Hmmmmmm.  I don't like to carp and criticise, but . . . This paper by
>K.D. Skeldon et al.  Interesting for its concept of portability, a
>major plus point, and also for measurement of discharge current of
>10-100mA average (though Terry's milage may certainly vary) sad for
>its continued reliance on intermediate frequency transformer theory
>etc.  They do give an expression for the input impedance of the coil
>under cw conditions (or double-tuned intermediate frequency
>transformer, IFT) which I think dates from 1943 and K.R. Sturley's
>"Radio Receiver Design" volume 1, publ. John Wiley, if not earlier.
>Given this paper was published last year, and received for publication
>in October 99, one wonders if academia will ever wake up (says he
>after 20 years in 5 universities in two countries blah blah blah yawn
>snore ;-) to the fact that an impulse-driven TC is *not* an IFT.
>
>I particularly like the comment (half way down p132, p7 in the .pdf)
>that "a well-designed coil should be able to generate an output spark
>length of 30cm for each kilowatt of input power" which is attributed
>to anonymous www-based resources.  I'm sure that'll bring a wry smile
>to John Freau's lips amongst others (I think you're currently getting
>42ins/107cm for ca. 500W) as will the hit-and-miss asynch rotary gap
>break rate/primary cap size design.  If you're one of those who has
>built a rotary gap, you ought to read this paper just for
>entertainment's sake.  When it comes to "the distribution of voltage
>along the secondary coil follows the first quadrant of a sine
>function" Paul Nicholson will be in stitches.
>
>When I think what the authors of this paper might have gained via this
>list I honestly don't know whether to laugh or cry, even given they
>did this say three years ago.  If it had been vetted by some of those
>on this list I can envisage a number of amendments might have been
>recommended prior to publication.  They do manage to end up with 1,5m
>arcs for 1,5kW input, which though not likely to impress anyone here
>is at least something for their pains. FWIW, if you don't want to
>plough through all of it, it's a 10kV 1,5kVA 50c/s trannie and a
>60nF/40kV Maxwell cap-based system, a decent enough LTR design
>(arrived at semi-empirically) if only they'd used a synch rotary.  The
>topload is tiny though, and they don't give dimensions in the paper;
>it looks a lot less than a 4" x 24".
>
>Perhaps Richie (being possibly our northernmost correspondent in the
>UK) would like to invite the authors of this paper to see a _really_
>efficient coil.
>
>Thanks to Antonio and Luc for bringing this to our attention.  One day
>perhaps academia will arrive . . .
>
>Dunckx
>