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Re: A real 1/4 wave TC



Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>

Cool Skip!

I figured you were up to something (different). Thanks for sharing the gap info. That certainly helps evaluation (which we all have a tendency to do). The 1:1 h/d should give a very linear voltage profile along the coil. Might be interesting to use FANTC to look at the voltage profile. I actually use take the V/I profile data into Excel and scale the voltage accordingly. That is what the VI output is really for. Someday, I'll port the VI graph to JAVATC and will then allow the transformer data to populate the scale accordingly.

I agree that a topload is not necessary for resonance, but it is a mechanical necessity (not a resonance necessity). If your terminal is a small sphere, then there would be negligible topload capacitance. Corona inception is at about 26kV in my neck of the woods, and the coil will absolutely be far above that, and it will then try to breakout of the top secondary. The problem you face with the top end of the secondary is no different than using a sphere topload which is terrible at secondary breakout prevention unless it is low enough and large enough (how low depends on how large and of course the coil). But hey, ignore me and keep experimenting. I'm simply looking at it from an armchair cowboys point of view. I've never tried such a short h/d as a 2LC setup and no topload. Very cool experiment!

Take care,
Bart


Tesla list wrote:

Original poster: Skip Greiner <skipg@xxxxxxxxxxxxxxx>

Hi Bart and all
For 40 years I have tried to find the time and method of calculation to build a TC that would resonate at the 1/4 wavelength of the wire on the secondary. I now have the time and JAVATC allows the necessary iterations to build the device. In my thinking a top load should not be necessary and in the case of this unit it was going great without one (unless you consider the band of aluminum foil a top load). And yes, the tranny still lives. The safety gap is set to about 0.125" and the SRSG gaps are set extremely tight. The dimensions of the secondary (and 1:1) aspect ratio were determined by JAVATC. It seems right now that a "square" secondary is necessary to get the secondary LC to resonate at the 1/4 wave. When the cap blew up, I found that it also crushed one section of the secondary so a new secondary will also now have to be built.

My major concern is how to confine and concentrate the discharges to a single point. I had a terrific amount of energy eminating from the top of the coil. It was almost a complete18" ring of 36" to 40" sparks and that was at only 65v to 70v input to the NST. And per JAVATC my coupling was only 0.135. Interestingly, the discharges are almost completely horizontal. There does not seem to be a tendency for ground strikes, strikes to the primary or strikes from the top to the bottom of the secondary either inside or outside. If I can get that energy to a single point this thing is really going to be "cool".
Skip

Tesla list wrote:

Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>

Hi Skip,

I was running numbers and was about to get close to what you show minus coupling. I showed about 1.6 times higher and likely due to not having your actual inputs, etc.. Anyway, the cap death isn't a shock. Your lucky the NST didn't fail on 1 side (or did it?). Anyway, I'm curious as to what your trying to accomplish running at resonance on such a short 1:1 h/d high Q coil? If you get a cap that can take the higher voltage, you know the NST will be the next death. Don't get me wrong, I like it when coilers go out there and do something different. Just curious what your up to as know you've been coiling for quite a while now.

I have a coil similar to yours also using 18g and a helical primary with about 4 turns. However, coupling is about .3 or so. It was used as a maggy driver where the 3rd coil is directly over the top of the driver. This coil also used an aluminum disc between the driver and the 3rd coil (corona/breakout prevention from L2). The 3rd coil was just a small 4.5" coil but used a 9" x 30" topload. No problems breaking out. I insulated L1 to L2 with LDPE sheeting to prevent arc-over. I used Javatc to figure out the necessary L's and C's, but it took some creativity to force the program to model a 3rd coil. Freaked me out when it actually worked! The whole idea there was to consolidate a maggy, but in doing so, the 3rd coil affects the driver (just as a primary affects the secondary of a classic 2LC system and just as a topload affects a secondary [lot's of stuff to consider there]). It's a true 3LC disruptive coil with all the bells and whistles. This showed me that numerous coil stacks and inductances could be configured to model a single resonant frequency (obvious conceptually and mathematically, but proved mechanically when it actually worked).

http://www.classictesla.com/photos/hybrid/hybrid.html

Take care,
Bart