Bart,
This pair of Pancakes isn't mine, but was borrowed from an early Tesla X-Ray machine that was later sold as a Cenco demonstration Tesla Coil.
I am building a reproduction as soon as I get some wire. The secondaries are a bit odd. They're wound with two wire gauges:
23 layers of 26 silk covered enamel wire, wound 70 turns per layer 1600 turns total. To this is soldered a 28 silk-covered wire, and an additional 23 layers are wound with 87 turns per layer, an additional 2000 turns = 3600 turns per secondary.The topload capacities of the coil are simple brass rods to accept standard dischargers, I used 1/2" diameter rod 4" long - they were missing in the original machine.
The IDs of the coils are 1", and the ODs are around 6 1/2", primary included. The primaries are likely helical and wound on a 6" cardboard forms surrounding the secondaries.
The primary coils have 24 3/4 turns of 18 gauge stranded wire, normal lamp wire of the time period.They are potted in around 3" thick of beeswax poured in hexagonal forms.It seems from the wiring diagram that the primaries are in anti-parallel and the secondaries are in series.http://www.electrotherapymuseum.com/2008/30W/H-Tesla-Coil-C.jpg
I chose this coil specifically for this test. I feel it is very close to what Tesla was doing in the 1890s. The coil defies logic in some
ways. The original power supply has a 1kV transformer rated at 2 KW. It has two condensers, normal operation is around 1/2 mfd,
and .15mfd can be used for a higher frequency. Both settings spark well, but the lower frequency is really dramatic.
There is a reactance coil to limit the current, and a single 1/4" tungsten spark gap. The reactance coil, even at the lowest setting
(maybe 1.5 amps?) will throw a thick 7" spark between the terminals with the spark gap barely open. This is the same apparatus that will
throw a 4" spark running on only 20 volts (less than 200V in the secondary of the power transformer) [and a micrometer spark gap of less
than 1/1000"]. I've seen a lot of interesting old Tesla Coils, but this one really stands out. I know of 4 others to exist, and all function
just as well. At high power, 15 amps, a flaming arc bows up between the terminals and the measured path is probably 16" with heat
radiating in all directions.
An additional multilayered choke coil is placed in series with the Tesla Coils to allow detuning for smaller sparks and higher frequency
demonstrations. For normal operation this is removed from the circuit completely.
Jeff Behary
Date: Wed, 12 Mar 2008 18:59:59 -0700> From: bartb@xxxxxxxxxxxxxxxx> To: tesla@xxxxxxxxxx> Subject: Re: [TCML] 5" Sparks - Approx 35 watts input power: Tesla was correct!> CC: > > Hi Jeff,> > Jeff Behary wrote:> > Maybe Bart can run it through JavaTC.> > > I would love to. Send me specs!> > Your really having some success with your wax potting method. I've > notice this on al your flat coils.> Bart> > _______________________________________________> Tesla mailing list> Tesla@xxxxxxxxxxxxxx> http://www.pupman.com/mailman/listinfo/tesla
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