RE: [TCML] Chicago Science & Industry Tesla Coils (& flat ribbon primary)

[Jeff Behary <electrotherapy@xxxxxxxxxxx>]

Hello,
Neat photo!  Do you have a picture of the rest of the coil?  It looks almost like a wax/rosin composition between the ribbons.  A common formula from Thomas Stanley Curtis was copper ribbon separated with a cardboard spacers and then poured with wax/rosin.   Maybe they borrowed this idea from one of his early books.  (1915 era)  
 
Also, the brass ball - brass bed posts were commonly used back then...it could have been one of those.  Curtis used to recommend "stealing a bed post when noone was looking".  These days it isn't that easy...!
 
The normal fashion to wind secondary coils back in the 20s was to use silk or cotton covered wire, normally space wound with a wire or string of equal size or slightly smaller diameter...the second wire was removed, making a space wound secondary coil...   the 2:1 or 3:1 ratio was also common back then.   The wire was normally space-wound to prevent arcing from turn to turn, the large diameters partly for show and partly to add capacity.   These two unusual features can produce a healthy spark that will vary its appearace alot depending on other circuit parameters.   (Primary turns, spark gap, reactance coil, etc...) - and can be easily used to demonstrate some of the strange lighting effects in the Tesla lectures.  
 
I would bet is was operated from a standard wireless transformer, 2KW or so, (the 20s equivalent to an NST).  Maybe 20kV at 100mA or more.  Did you notice any Rotary Spark Gaps hanging around?
This size coil was often mentioned for stage shows during the 20s...back then, even with Tesla around, people could make a lasting impression demonstrating welding arcs, Tesla Coils, flourescent effects, rotating geissler tubes, etc...a few of them were famous for it.  (Curtis, Ovington, Strong, Strickfadden...)
 
Great picture!  Sounds like one of the more interesting museums to visit!
Jeff> From: ConorPerry@xxxxxxxxxxx> To: tesla@xxxxxxxxxx> Date: Wed, 30 Jul 2008 21:56:59 -0400> CC: > Subject: [TCML] Chicago Science & Industry Tesla Coils (& flat ribbon primary)> > Touching on the ribbon primary thread...> > Recently on a trip to Chicago we visited the Museum of Science and Industry. > They have two Tesla Coils on display. One is in the lower level on the way > to the submarine just after the circus display room. The second is on the > top floor near the giant Wimshurst machine.> > The first is quite strange in that it has a very tight primary/secondary > coil near the floor, then an overly elaborate top load with a round top and > small spikes. It's mostly hidden behind other displays of medical equipment > so I didn't get a good picture.> > The second is in it's own display box. I'd guess the secondary was about > 24" in diameter and maybe 4-5 feet tall. The top load is a quite small 4" > brass ball. The wire appears to be silk and is NOT tightly wound. The > primary coil is made of copper ribbon tied tight with cord, it appeared to > be spaced from itself with wood filler. The plakard said Circa 1935.> > I only bring this up because of the recent discussions. Seems strange to me > that someone would have thought it a good idea to use this material > "way-back-when" and before the internet and before high copper prices. I > think the original poster might have been exploring ideas to make the > primary coil smaller and cheaper. Might not be a very original idea when > looking at this old coil.> > http://i34.tinypic.com/2rfymmf.jpg> http://tinypic.com/view.php?pic=2rfymmf&s=4> > I'd love to build a coil like this, very mad scientist looking!!! But > haven't been able to get JAVATC to agree with any of these parameters ... > wish I had taken measurements while I was standing in front of it!> > _______________________________________________> Tesla mailing list> Tesla@xxxxxxxxxxxxxx> http://www.pupman.com/mailman/listinfo/tesla
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