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Re: big coil history



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. > >-- > > > > >