Re: [TCML] Designing a Coil Around a SRSG

[Brandon Hendershot <brandonhendershot@xxxxxxxxx>]

I'll acknowledge all of your replies when I get the time, but in the mean
time, one more question while I remember it: How much would the output
voltage of the NSTs increase when the variac is turned up to 140V? If
that's going to make much of a difference I'll have to make my mmc a smidge
bigger. And for clarity,  a 22kV mmc of 942C's would be 'close enough' for
a 15kV RMS NST?

Thanks a ton,
Brandon H.

On Mar 25, 2013 4:23 AM, "Scott Bogard" <sdbogard@xxxxxxxxx> wrote:
>
> Hi Again Brandon,
>      Glad I could help!  Yes, that secondary should work fine, and yes
> adding that second top load should be fine also.  SQRT of 1800= 42, so you
> want between 21 and 38 inches of overall diameter, when considering
> multiple toploads, if memory serves, you just sort of add the diameters,
so
> 26+14=40.  A bit over-gunned, but it should work fairly stable with a
> breakout point (if it doesn't, remove the second top load and re-tune the
> primary.)  As for 240/480 etc BPS...  In theory this works great, and many
> have claimed success using this, it is in fact very similar to the logic
of
> using a small cap and an async system.  I never could get it to work, but
I
> think I know why...  Firstly in those days I didn't understand power draw,
> and my crappy ballast was holding me back, not my break rate and capacitor
> combo, I didn't know this at the time.  Secondly I had severe trouble
> because I didn't have a good phase controller, the black light/lego system
> worked, but not well enough to determine phase for a system where stuff
> lines up differently (at least for me.)  I didn't do the exact calcs, but
I
> think you should probably be Ok with the cap size you proposed, and a
> normal 120 BPS for maximum output (may want to go higher and use a smaller
> cap even.)  My advice is to go to the fantastic "Java TC," load the demo
> coil (unless you are already a javaTC guru!) and plug in your cap values,
> and transformer specs, and play with the rotary gap designer near the
> bottom of the page.  Find the BPS level by trial and error that best gives
> spark length as close to or higher than the "freau ideal" as possible, and
> design around that.  If you are having trouble reaching that level, change
> your cap configuration a little and see if you can hit it (also pay
> attention to LTR values, chances are you want that.)  And like others
said,
> don't over volt your cap!  Java TC can help with that also, in the MMC
> calculator it has, it really is a fantastic tool!  Best of luck, let us
> know what you find!
>
> Scott Bogard.
>
>
> On Sun, Mar 24, 2013 at 5:40 PM, Brandon Hendershot <
> brandonhendershot@xxxxxxxxx> wrote:
>
> > 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.
> > > > _______________________________________________
> > > > 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