Re: big coil history

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Dr. Resonance" <resonance@xxxxxxxxxx>



George Kauffman built the large coil on display at the Carnegie Museum.  He
built it in 1903 --- it was 12 ft tall.  It was used in some of the WWII
movies showing the troops "what's going on back home".  Kauffman stood atop
the coil in a metal suit was waved his arms rapidly around.  The coil had a
strong wood framework.

His father knew Tesla personally when he was "digging ditches" in NYC.  I
met Kauffman and talked at length with him before he passed away in the
1980's.

Dr. Resonance


> >
> >
> >Thanks for the feedback on the introduction of Medhurst C to the
> >Tesla world.  I had a feeling Malcolm had something to do with it.
> >I wonder, how were people calculating coil resonances just prior
> >to that?   The inductance is not to hard to deal with, but how was
> >capacitance estimated?  People couldn't have still been using the
> >wire length thing at that late stage because their coils worked!
> >And some of them were quite large, so there must have been another
> >fairly reliable method in vogue.
>
> I suggest empiricism played a huge role.  Remember that there were a lot
of
> "rolled poly" caps back in the 80s and early 90s. The whole capacitance
> thing was pretty uncertain, so you'd just do cut and try until it
> worked.  There were some rough and ready toroid C estimation formulas
> around by the late 80s that I ran across in the early 90s.  I think people
> just calculated the approximate C of the toroid and a cylinder, then
> calculated an approximate fres (or measured it using a signal generator),
> then wired up a primary and tuned for maximum smoke.
>
> The idea of actually calculating coupling, and then having some
theoretical
> basis for selecting a particular k, for instance, wasn't much evident.
>
> There's no question that some coil builders had a better "feel" for
> proportions and sizes that would work.  Also, it's pretty easy to get a
> coil to "work" at all, especially if you aren't concerned about
efficiency.
> I've seen a number of big pig powered coils that only produce 5-6 ft
> sparks, which indicates a pretty non-optimized design, considering that 10
> ft should be fairly easy.
>
>
> >I for one would welcome hearing more about the 'early days' from
> >the old timers.  Why not put a few priceless recollections into
> >the archives for preservation?    I'd like to know more about the
> >history of this hobby, its technical developments, and the people.
> >Who were the movers and shakers back in the 50's, 60's, and 70's?
> >When did people start building big coils for public performances
> >and special effects, and how did they design them to work without
> >too much trial and error?
>
> http://www.ttr.com/ is Bill Wysock's site, and describes his work with
> coils (which certainly goes back a few years) as well as a lot of
> information about the Griffith Park Observatory display coil as well as
Ken
> Strickfadden.
>
> On the non-hobby side..
> The Aurandt coil at the Griffith Observatory is well over 60 years old,
and
> was used for public demonstrations on a daily basis (and still was as of a
> couple years ago, with some refurbishing by Bill Wysock).  It started with
> Leyden jar caps (high tech beer bottle caps) went to glass plates, and
then
> used something more modern.
>
> Ken Strickfadden (Frankenstein special effects) used tesla coils, probably
> from 1931 onwards.
>
> There have always been several HV effects people in Hollywood over the
> years, but I don't have names for them.  They'd typically do all sorts of
> electrical effects.  The one I particularly like is the one where you hold
> a couple carbon rods in the air over your head, connected to the 110VDC
bus
> on stage and strike arcs to simulate lightning. Wearing a hard hat is
> recommended to avoid singed hair.  Prior to the advent of big xenon flash
> tube based lights, stage lightning was almost always done by carbon arcs
> driven from battery banks. I used to work at a place that had a trailer
> full of batteries, with a gasoline generator for charging, and a big
> plexiglas box with a plunger that brought a bunch of carbon rods together.
>
> Physicists like Merle Tuve were building coils in the WW II era.  Tesla
> coils are described in Craggs and Meek's book, along with design equations
> based on coupled LC circuits.  Those people would have been using
> references like Circular 74 or its predecessors.
>
>
> Given that folks in the 30s and 40s were using the lumped LC analysis
> approach (and it had certainly been around before that), it would be
> interesting to see where, when, and why, the 1/4 wavelength of wire idea
> started to be used.
>
>
> >And where is Ed Harris now?
> >--
> >Paul Nicholson
> >Manchester, UK.
> >--
>
>
>
>
>