Tim,
Making 5 foot sparks certainly does NOT require a secondary coil that's 5 feet long. Indeed, it's not out of the question for a well designed and tuned larger coil to produce sparks upwards of 3X the secondary coil length! Obviously, the increased demand for inductance and current handling of a larger coil would dictate a physically larger secondary coil, but adequate topload size and C will also cause a considerable drop of its own in your operational resonant frequency. Bart Anderson's JAVA TC coil design program can run all of the numbers for you and I believe its still a free download, but a good rule of thumb for topload size (especially for larger coils) is that the toroid's major diameter should be close to, or equal to, the length of the secondary coil and the toroid's minor diameter should be close or equal to the secondary coil's diameter.
As far as choice of wire for your secondary coil, I would choose a gauge that allows me to wind somewhere between 1000 and 1500 turns with no turn/turn spacing to get the finished desired length of my secondary coil. Magnet wire is often the wire of choice because of its very thin, but effective insulation, which allows for tighter winding and consequently, a higher inductance to size ratio. I'm thinking #22, or even #24 gauge, is sufficient for a 15/120 NST system. And you should also target a secondary aspect ratio in the 4:1 to 5:1 range. So a smaller gauge wire will allow for more turns per inch, which increases inductance. My aforementioned Green Monster coil is only wound with #19 gauge green enameled magnet wire (hence the chosen name - GREEN Monster), is 49.5" long by 12.5" diameter, and I routinely run a good 15 kVA through it when making those 12 footers. I would bypass Radio Shack as a source of wire and look on eBay or possibly a local electric motor and/or transformer repair shop would sell you a decent sized (8 to 10#) spool of magnet wire at their cost. Besides, you would have to pay a king's ransom purchasing a multitude of those tiny spools of wire from RS and do a whole lot of splicing to get enough wire to wind a secondary coil of that size.
David
Timothy Gilmore <tdg8934@xxxxxxxxx> wrote:
>All,
>
>If I use both 15kv/60mA NSTs (yes they were identical and phased the same
>with my jacobs ladder - bigger flame spark), then the sparks could be 4-5
>feet in length so shouldn't the secondarys also be 4-5 feet tall. All of
>the designs I see are about 2 feet for the secondarys but are wider in
>diameter like 4" to 6" or more. This doesn't make sense to me. Why go wider
>in diameter and not taller in the secondary? I would think you would want
>thicker wire like 22 or 20 gauge wire and not 24 or 26 gauge. Also does it
>have to be magnet wire. Radio Shack 22 gauge wire has plastic like
>insulation. Is that ok?
>
>Thanks,
>
>Tim
>
>On Sat, Feb 21, 2015 at 10:10 AM, David Rieben <drieben@xxxxxxx> wrote:
>
>> Hi Tim,
>>
>> If I may jump in here. My personal advice would be to go ahead and build
>> the biggest thing that you can with what you have available. Reason being
>> is - and trust me on this - I promise that once you've built your single
>> 15/60 NST driven coil and coaxed it to optimal performance, you WILL wanna
>> go BIGGER! This "build a bigger one" syndrome seems to be a pretty much
>> universal ailment amongst the coiling community, so you may as well prepare
>> yourself for this almost certain outcome on the front end :-) I started
>> with NST driven coils nearly 20 years ago and my most aggressive coil to
>> date is the Green Monster, which stands nearly 8 ft. tall with its 12" x
>> 56" topload and is driven by a properly ballasted 10 kVA, 14,400 volt pole
>> pig! And it is quite an attention getter with its bright, fat and quite
>> noisy ground striking ~12 ft. sparks, but being a classic ARSG driven coil,
>> its "guts" ain't too portable! (Estimate the total weight of the entire
>> system, including the massive ~1
>> 200 lb. control panel, to be in the the neighborhood of 1600 lbs!) But if
>> fund$ were no object and space and available electrical service would
>> allow, I'd probably build an even bigger one! ;-) Actually, my control
>> panel is beefy enough to drive an even larger coil than the Green Monster,
>> but I'd need access to professional high voltage laboratory facilities to
>> house and run such a beast ;-))
>>
>> Anyway, good luck with your project, whatever size that you decide to go
>> with.
>>
>> David
>>
>>
>>
>> Timothy Gilmore <tdg8934@xxxxxxxxx> wrote:
>>
>> >Gary,
>> >
>> >Sounds like a pretty scary adventure veering off from the plans I have
>> >which indicate simple things such as just adding more capacitance. I think
>> >what I will do first is get a working single NST tesla coil first
>> >(15kv/60mA) and using the 2nd NST as a backup incase the first ever gets
>> >fried. If it looks like the design is stable than perhaps later on I will
>> >take on a 2 NST new design. Its been 35 years since I built my first and
>> so
>> >much great development has happened and new ideas learned by the smart
>> >people here and other places in the Tesla Coil world. Thanks again for
>> your
>> >insight and the others here that make this such a fun hobby.
>> >
>> >Tim
>> >
>> >On Fri, Feb 20, 2015 at 8:02 PM, Gary Lau <glau1024@xxxxxxxxx> wrote:
>> >
>> >> The only reason to have transformers be identical is a matter of
>> >> aesthetics. As long as the output voltage is remotely similar, one can
>> mix
>> >> France, Jefferson, whatever, flavors of NST's, if the phasing is
>> correct,
>> >> and you'll know immediately if it's wrong. It's _nice_ to have them
>> >> identical but functionally unnecessary.
>> >>
>> >> > There would be a lot more changes than just caps and gaps.
>> >>
>> >> I would like to amplify the above point. Assuming you want to do
>> >> everything needed to extract the maximum arc length from the additional
>> >> power at your disposal, repeat over and over - Bigger is Better. You'll
>> >> want a larger top load, and you'll want a taller secondary to space the
>> top
>> >> load farther from the primary to avoid strikes to it. The larger top
>> load
>> >> and secondary will require a significantly larger primary, not just
>> another
>> >> couple of turns. I ended up building a 2-layer primary to keep
>> >> the dimensions sane. Higher inductances and lower frequencies are all
>> >> good!
>> >>
>> >> Also, a 15/120 power supply is probably going to push the limits of
>> what a
>> >> static gap can handle. You didn't mention what you're planning for a
>> gap
>> >> but you might wish to consider a rotary. I highly recommend the
>> propeller
>> >> gap configuration - http://www.laushaus.com/tesla/sync_gap.htm If
>> you're
>> >> thinking about a synchronous rotary, the capacitor size needs to be much
>> >> higher than for a static gap, and will require comparably more primary
>> >> inductance.
>> >>
>> >> And, a 15/120 power supply is going to pull a LOT of juice from the
>> wall -
>> >> you'll want to make sure you have an adequate PFC capacitor to minimize
>> >> current draw. My single 15/60 pulls in excess of 20A with a sync rotary
>> >> and 240uF of PFC caps.
>> >>
>> >> Bottom line - you should plan from day 1 what the final configuration is
>> >> going to be - you'll not be able to go back and forth with 1 or 2 NST's.
>> >>
>> >> Regards, Gary Lau
>> >> MA, USA
>> >>
>> >>
>> >>
>> >>
>> >>
>> >> On Fri, Feb 20, 2015 at 1:32 PM, Timothy Gilmore <tdg8934@xxxxxxxxx>
>> >> wrote:
>> >>
>> >> > Great videos on Phasing (both parts 1 and 2). I will watch those again
>> >> when
>> >> > ready to set up.
>> >> >
>> >> > On Fri, Feb 20, 2015 at 9:36 AM, John Paul Grippa <
>> pupman@xxxxxxxxxxxx>
>> >> > wrote:
>> >> >
>> >> > > There is a great video from the Geek Group on YouTube that explains
>> how
>> >> > > this works extremely well. It will also give some good tips on how
>> to
>> >> > > ensure proper phasing. Check it out!
>> >> > > https://www.youtube.com/watch?v=KSlQjw9OPG4
>> >> > >
>> >> > >
>> >> > > > Date: Fri, 20 Feb 2015 08:26:17 -0600
>> >> > > > From: tdg8934@xxxxxxxxx
>> >> > > > To: tesla@xxxxxxxxxx
>> >> > > > Subject: [TCML] Dual identical FRANCE neon sign transformers
>> (15000v
>> >> > > 60mA each) in parallel
>> >> > > >
>> >> > > > I currently have a France NST at 15kv 60mA and built a nice jacobs
>> >> > ladder
>> >> > > > with it. Yesterday on eBay I found what looks to be identical
>> model
>> >> NST
>> >> > > for
>> >> > > > a good price (no GFI). From what I have read about NST phasing,
>> >> having
>> >> > > > identical NSTs don't require testing the HV outputs and I should
>> be
>> >> > able
>> >> > > to
>> >> > > > connect them up in parallel identically using the same sides.
>> What a
>> >> > > jacobs
>> >> > > > ladder at 120mA would be! Anyway I'm assuming that I should start
>> >> > > building
>> >> > > > my tesla coil with 1 NST and when it works add the next NST in
>> >> parallel
>> >> > > and
>> >> > > > double the capacitors and change the tap on the primary. Does this
>> >> > sound
>> >> > > > like all I would need to do?
>> >> > > >
>> >> > > > Thanks - Tim
>> >> > > > _______________________________________________
>> >> > > > Tesla mailing list
>> >> > > > Tesla@xxxxxxxxxx
>> >> > > > http://www.pupman.com/mailman/listinfo/tesla
>> >> > >
>> >> > > _______________________________________________
>> >> > > Tesla mailing list
>> >> > > Tesla@xxxxxxxxxx
>> >> > > http://www.pupman.com/mailman/listinfo/tesla
>> >> > >
>> >> > _______________________________________________
>> >> > Tesla mailing list
>> >> > Tesla@xxxxxxxxxx
>> >> > http://www.pupman.com/mailman/listinfo/tesla
>> >> >
>> >> _______________________________________________
>> >> Tesla mailing list
>> >> Tesla@xxxxxxxxxx
>> >> http://www.pupman.com/mailman/listinfo/tesla
>> >>
>> >_______________________________________________
>> >Tesla mailing list
>> >Tesla@xxxxxxxxxx
>> >http://www.pupman.com/mailman/listinfo/tesla
>> _______________________________________________
>> Tesla mailing list
>> Tesla@xxxxxxxxxx
>> http://www.pupman.com/mailman/listinfo/tesla
>>
>_______________________________________________
>Tesla mailing list
>Tesla@xxxxxxxxxx
>http://www.pupman.com/mailman/listinfo/tesla
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla