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Re: [TCML] Designing a Coil Around a SRSG
Hi Scott,
Superb. I understood every word.
I'm thinking of keeping my 3.5" x 14" 29AWG secondary and adding a 4" x 16"
Topload beneath the existing 7.25" x 26". Do you think that would be
enough? I can't afford much error...
What do you (all) think about using 240/360/480bps and a smaller capacitor?
Or is it 120bps in itself that performs best with NSTs and not simply a
srsg..? Otherwise I was thinking of using 4 strings of 11 caps
(942C20P15K-f) to get 22kV at 54nf. I know this is close to the peak output
of my NSTs, but I need to be as economical as possible. Just how unwise is
this?
I'll do some research on machining the rotor before I ask anything about
that.
Thanks a lot,
Brandon H.
On Mar 24, 2013 8:43 AM, "Scott Bogard" <sdbogard@xxxxxxxxx> wrote:
>
> Hi Brandon,
> it looks like this post got side tracked into triggered gap land, so
> I'll answer your questions in case nobody else has. Ok firstly looking
> over your proposed specs (whether or not you were asking for it) my two
> cents...
> 15/120... that is some serious power for NSTs, 1800 watts worth, and that
> number 1800 is the basis for lots of our calculations (if you want to do
it
> right, we must calculate. -
> 7.25" x 26" Topload... A bit under-gunned for that wattage, you could go
> bigger for longer sparks, or leave it that size for multiple smaller ones
> (the quick and dirty formula for top load size is (SQRT of watts) * (.5
> though .9) = topload overall diameter in inches (.5 being multiple
> streamers, .9 being just one.)) I would go bigger, but I like big top
> loads only making one streamer.
> *- ~6" x 24" 25** AWG Secondary Coil (*subject to change(**especially
> so))... This is a bit over-gunned for your wattage. It does not hurt to
> make a bigger coil, it is just unnecessary. For reference I use a four
> inch coil with about 2500 watts, but I like small coils with ridiculous
> sparks. The tend to look a bit silly, tiny coils dwarfed by their top
> loads, but when you turn them on, this attracts more attention to the
> sparks.
> Ok, the capacitance of your coil is very specifically dependent on BPS.
> Let me enlighten you to a newbie mistake, I made for several years after
> starting coiling, there are two systems one must "tune" in a TC. Firstly
> is the well now resonate systems, getting frequencies fo tank and promary
> to match secondary and topload, everyone knows this. Secondly, and just
as
> importantly (and often overlooked) is the tuning of power draw, this is
> done with ballast (not an option as you are using NST) tank cap
> capacitance, and BPS. a lower bps will have long to charge, and requires
a
> larger capacitor, up to where your ballast can no longer allow additional
> power to be absorbed. I don't like synchronous for this reason, you need
a
> HUGE capacitor for a given power draw, it is much easier to use a high BPS
> and a small cap. But, with NSTs, synch is the lowest stress mode of
> operation, as such, it is good to use. With that said, you have probably
> heard of LTR caps? LTR (larger than resonate) is the size you want to use
> for a sync rotary, as it represents the size that will fill to around
> 60-75% capacity during operation (which if we consider how capacitors work
> (namely how they charge fastest when empty) is the best place to have it
as
> it represents the most power transfer per second (charging higher will
take
> up more time than it is worth, and charging lower won't move enough juice
> into the coil.)) You could use a "resonate" sized cap, this will give the
> absolute best power transfer rate every time (the ultimate in power draw
> tuning) BUT it will most likely fry your NSTs, as it will actually change
> your wattage from 1800 to something higher, and require other design
> changes as shown above. As for how to calculate these, you can look it
up,
> there are resonate and LTR calculators everywhere. Personally I don't use
> nor like LTR caps, I like an external ballast, and a high BPS system, but
> that is not an option for NSTs, as the ballast is built in.
> Ok, onto srsg design, the easiest way is to get a surplus induction motor
> and grind flats onto it, there is loads of info on this in the archives,
> and others have done actual studies. When I built my only sync gap, I got
> lucky and the thing worked perfectly, but if you grind off too much the
> motor is junk, and too little and it won't sync. Then phase is adjusted
> with a phase controller, or rotating the motor in its mount, you want it
to
> fire at the peak of the AC cycle. To adjust mine, I taped a flourescent
> lego to the rods and used a black light, and lined it up so the brightest
> spot lined up with the rods (this will make more sense if you read into
> them a bit.) Ok, I feel like I've given you enough to chew on for a bit,
> hopefully others will chime in as well!
>
> Scott Bogard.
>
>
> On Fri, Mar 22, 2013 at 11:50 PM, Brandon Hendershot <
> brandonhendershot@xxxxxxxxx> wrote:
>
> > Hi All,
> >
> > Now that I've finally gotten something out of my long overdue 3.5" coil,
> > I'm already itching to start work on the next.
> > I've decided to make the switch to a rotary spark gap and have settled
on
> > synchronous over asynchronous for the sake of performance and security
of
> > my NSTs.
> > I want to be sure I do this coil right and plan everything out before I
buy
> > anything. Here are the parts and specs for what I know is going into the
> > new coil:
> > - 15/120 (4 x 15/30) NST Bank
> > - 7.25" x 26" Topload
> > - 0.25" x 0.25" Flat Primary Coil (Plenty long, should be enough
> > regardless)
> > *- ~6" x 24" 25** AWG Secondary Coil (*subject to change(**especially
so))
> >
> > I've read that 120 BPS is just about the best you can get when you're
using
> > NSTs, so I'm going to be building the rest around that. I haven't found
a
> > motor yet, any specific RPM to look for? HP will vary since we don't
know
> > what style we want yet.
> > I'm assuming not (you know what they say about that), but does the
> > capacitance of the MMC vary depending on the BPS? Since it's synchronous
> > with the AC waveform and firing at a single frequency I imagine not...
> > Rather, isn't the Input watts the only determining factor? Silly me.
Next
> > question:
> > Does the BPS have any influence on what the resonant frequency of the
> > secondary coil should be? <This would be my primary concern.
> >
> > One more quick irrelevant question, moving from a 15/30 to a 15/120,
would
> > there need to be any modifications made to the Terry Filter?
> >
> > Thanks a bunch,
> > Brandon H.
> > _______________________________________________
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> >
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