[TCML] MMC for 4 mot SRGTC

Sun Apr 6 12:24:39 MDT 2008

Hi All,

I agree. With my pig coil running 0.06uF STR, I started out using a 
synchronous gap (120 bps, then changed to 240 bps). Worked fine, but I 
eventually changed over to a variable RSG and sparks were best with a 
bps of about 360 as calc'd by motor rpm. In my case, I have a readout 
for this. I never went back to synchronous operation on this coil. There 
is a difference however of just running a non-sync motor at it's rated 
speed and running a variable speed motor where one can control the 
speed. The later would require a DC motor or 3-phase motor (I use 3-phase).

The advantage I see with sync operation is that you have a controlled 
bang size and will have less missed firings, where non-sync operation 
will always have these. But with controlled variable speed non-sync 
operation, you have the ability to adjust in the bps and power 
throughput. This is my preference on the pig coil. I wouldn't do this 
with an NST (stick to sync or static gaps for the health of your NST) 
and the reason is that missed firings will allow the cap to charge to a 
higher value before the next presentation which runs the possibility of 
killing the NST. Of course if the safety gap is set properly, it will 
fire more often, and then the safety gap heats up and starts taking over 
as it begins firing at a lower and lower voltage.

Take care,
Bart

David Rieben wrote:
> Hi Scott, Kris, all,
>
>
> I tend to agree with Scott on this issue. I've heard many of
> the pro's and cons regarding synch vs. asynch and IMHO,
> it comes down to a matter of preference on large, pig sized
> coils although there does defonitely appear to be an advantage
> to going synch with mid-sized coils driven by the limited avail-
> able power from NSTs. If longer sparks are what you're after,
> which is where the majority of us coilers are ;^), then the fast-
> er BPS rates afforded by an asynch RSG are a definite
> advantage with the much greater power throughput potential
> of large non-current limited transformers, like pole pigs. Some
> coilers do like to go synch with high powered coils, but from
> the spark length reports of synch vs asynch with larger coils,
> there doesn't really appear to be any advantage to "going synch"
> with a piggy powered coil. An asynch gap is also a bit sim-
> pler to construct. Also, there's the issue of securing a primary
> cap of sufficient rating to run LTR with a pole pig, as an LTR
> prerequisite would make for an impractically large and expen$ive
> capacitor. It's a lot simpler and more practical to just go asynch
> with an STR cap, utilizing a >100/120 BPS charge/dicharge cycle
> of the primary cap to increase the power throughput for longer and
> brighter sparks with large, high powered coil systems. Indeed, my
> large coil, with a 0.1 uFd primary cap seems to like 350 to 400
> BPS for the best output.
> http://www.dawntreader.net/hvgroup/david/gm.html
>
> My $.02,
> David Rieben
>
>
> ----- Original Message ----- From: "Scott Bogard" 
> <teslas-intern at hotmail.com>
> To: "Tesla Coil Mailing List" <tesla at pupman.com>
> Sent: Sunday, April 06, 2008 8:51 AM
> Subject: RE: [TCML] MMC for 4 mot SRGTC
>
>
>
> Hi Gary, Kris,
>     I use a sync gap on my 4-MOT coil.  I wish I didn't!  Granted I 
> use a ballast, but my performance is limited to about 54 inches.  4 
> MOTs can do much better, I've seen it.  You would be better off to 
> design yourself an asynch gap, and then the cap size really doesn't 
> matter as much.  My understanding is that using sync gaps requires a 
> properly sized cap for maximum performance, and my cap size was picked 
> on faulty calculations, so lesson learned, it is best to just go 
> asynch anyway.  I am in the process of designing an asynch gap, but it 
> will be a long time until I can afford to build it with school 
> expenses.  As for using .4117 uf for a cap, my guess is that would 
> eventually destroy the secondary, but I really don't know (I have had 
> burnouts with .075, let alone .4 or even .12).  Just a thought.  There 
> are others with more experience that can probably comment on this.
>
> Scott Bogard.
>
>
>> From: Gary.Lau at hp.com
>> To: tesla at pupman.com
>> Date: Sun, 6 Apr 2008 13:18:47 +0000
>> Subject: RE: [TCML] MMC for 4 mot SRGTC
>> CC:
>>
>> I have never built a MOT-based coil, so take this comment with a 
>> grain of salt, but is using a sync gap necessary?  Using a higher 
>> break rate would diminish the required cap value.  I think I've heard 
>> more async gaps used with MOT's than sync gaps.  Maybe the same with 
>> pole-pig coils.  A LTR cap there would be HUGE.
>>
>> Regards, Gary Lau
>> MA, USA
>>
>> > -----Original Message-----
>> > From: tesla-bounces at pupman.com [mailto:tesla-bounces at pupman.com] On
>> > Behalf Of Kris Grillo
>> > Sent: Saturday, April 05, 2008 11:49 AM
>> > To: tesla at pupman.com
>> > Subject: [TCML] MMC for 4 mot SRGTC
>> >
>> > I am putting together a 6" coil with 4 MOT power supply and a 120 
>> bps > sync rotary
>> > gap.  I would like to run the mots wide open (no ballast). I 
>> estimated > 8400 V .5A for
>> > the transformer output. For the MMC, JavaTC is saying I need 
>> .4117uf for > LTR!
>> > That seems huge to me. I have 60 of the 942's for 5 strings of 12 
>> right > now, and I
>> > planned on doubling that to get to .1249uf before I get it up and > 
>> running, but that is
>> > still less than resonant. I could probably swing another 84 caps to 
>> get > to 12 x 12 for
>> > a just about resonant cap, but 336 more caps for the .4117uf value 
>> is a > little out of
>> > my price range right now. Is it so important to run larger than 
>> resonant > cap with a
>> > mot driven srg coil? The mots are under oil, if that matters. Any > 
>> suggestions?
>> >
>> >
>> > ---------------------------------
>> > You rock. That's why Blockbuster's offering you one month of 
>> Blockbuster > Total
>> > Access, No Cost.
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