RE: Theory vs. Measurement

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Hello Malcolm and All,

| >From MALCOLM-at-directorate.wnp.ac.nz Wed May 29 21:51:47 1996
| Date: Thu, 30 May 1996 14:20:13 +1200
| From: Malcolm Watts <MALCOLM-at-directorate.wnp.ac.nz>
| To: tesla-at-pupman-dot-com
| Subject: Re: Theory vs. Measurement
| Hi everyone,
|              I'd just like to say that I also like to be able to do
| at least ballpark predictions for coils I wind etc. One of my prime 
| motivations in writing my article (whatever its flaws) was my 
| discovery of Medhurst's self-C formula for single-layer coils. While
| I've subsequently learned of my shortcomings on Tesla coil theory (one 
| of the reasons I joined the list), I spent months hunting out a 
| formula that I could use to _always_ design a coil for a given 
| frequency. I found no such formula that worked with such consistency 
| anywhere else. In fact most predicted completely incorrect 
| frequencies for _all_ of my coils. In the same breath I have to say
| that Ed Harris synthesized one that works rather well.

Paraphrasing an old saying: If you can't get the numbers to come out
right, you don't understand it yet.

I like the numbers to work out too. But, and this is part of the
challenge, TCs involve phenomena which are difficult to deal with
mathematically. Most of these can be delt with reasonably well now
except for RF arcs at the top hat. Which is why we build TCs in the
first place. Lovely to watch and we understand somewhat, but not yet
well well enough to make consistently accurate predictions.

You've mentioned Medhurst's formula several times and I've looked
for it but not found it, at least not by that name. Would you post
it, and Ed Harris' formula too? Some examples of calculated versus
measured results would also be interesting if you have them handy.

|      Also, I found that a burning curiosity to know how things worked 
| after some hands-on inevitably led to murky theoretical waters, many 
| of which bore fruit. This is simply carrying on from when I wound my 
| first "shocking" coil when I was 8. Valves and transistors followed 
| very shortly afterward. I have always been a strong experimentalist 
| and will willingly toss out bad ideas if either experiment shows them 
| up or someone shows me I am demonstrably wrong. I feel I too have made 
| much progress, although not without countless hours of mental 
| anguish.
|      Finally, one of my hopes was that by measuring and posting data,
| others who are more mathematically astute than I would have something
| useful to work with that would ultimately be to the benefit of us all.

As you say, "Burning curiosity" is the source of progress. When you
inevitably find yourself in those murky waters, curiosity may seem
like a curse. But there is great satisfaction when you learn enough
to make those murky waters clear isn't there?

Experimental and theoretical work are two sides of the same coin.
For me, the big high in engineering is carrying through a theoretical
development, building the widget, and seeing it work as predicted.
This almost always requires several iterations refining and reconciling
theory and practice, but eventually things work, and you understand why,
and you feel a real sense of accomplishment.