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Re: [TCML] Strike Rail Hits Was: Stacking vs Large Diameter



Hi David,

I'm not certain all coils would exhibit this, and it's only my own coils that I can use as a reference. However, maybe increase the Green Monster power very slowly. There is a point where the sparks should start hitting the primary. Leave it there for a while. Note the primary hits. Then increase power to normal. Given your coil, you may be heading beyond the threshold rapidly and you certainly have the power. On your coil, I'm guessing about 30 to 40 amp range which is probably 1/2 of your norm. Do you ever run at 1/2 power for long? This is about where the issue would occur. The fact is, some coilers can't even reach that power range. So when they turn power up, they might be right inside that window.

Even with high power, sparks do come back to the coil from time to time. We both know that. If a coil is run with just less than enough power to hit the primary, this is the area that will likely have the least number of primary hits. Or if a coiler has a nearby wall to attract the streamers to, then maybe never hit the primary (all assuming good coupling and tuning). But in an outdoors environment without anything in spark range, this issue is most prominent and that's mainly where I am focused. Adding the breakout above the toroid is certainly a viable alternative to help. Anytime you can get that spark "up up and away", the better off you are.

Take care,
Bart

David Rieben wrote:
Bart,

That's some interesting observations that I never really
considered. Not too sure my observations have matched the certain "power window" that you state where the pri- mary strike frequency seems to spike. As you stated, when the sparks are allowed to emanate freely from the smooth (or relatively smooth) toroid surface, they tend to start from the horizontal center region. With this in mind, I have found that the primary/strike rail hits can be significantly reduced by setting a breakout point closer to the top of the toroid, thus forcing spark propagation
from the upper part of the toroid, well above the hori-
zontal center. But even then, I will still get an occasional
strike to the primary region. I guess you have to expect
that with a 240 volt, 90 amp power feed into a coil
that doesn't quite top 8 ft. in total vertical height!
This past Friday when P. Slawinski and C. Prince came for a visit, we tried elevating the whole tank circuit assembly of the Green Monster about 18" with my 4 jack stands. This is what allowed for more
numerous sparks in the >12 ft. range, in my opinion,
although this did NOT change the toroid to primary
coil/strike ring clearance and consequently, the pri-
mary strike frequency remained pretty much status quo.

David Rieben


----- Original Message ----- From: "bartb" <bartb@xxxxxxxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Tuesday, July 15, 2008 8:51 PM
Subject: Re: [TCML] Strike Rail Hits Was: Stacking vs Large Diameter


Hi David,

I've used my old primary on many coils and refitted it with inner turns as necessary (started big and then started building smaller coils). I was just thinking the Green Monster would look pretty cool with a small ribbon primary resonantly driving the secondary. Yes, the sparks do go where they want. But then, their going there for reason (because they can) ;-) . What I don't like is giving the coil "just enough power" to hit the primary. I have some extra turns and thus a little auto-transformer action occurring which I don't like. This seems to add to primary hits, but I'm not sure if it's the auto-transformer action or simply power. A smaller 4.5" coil I run can hit the primary as well all day long if I only give it just about enough juice to do so. But if I increase power enough, I rarely hit the primary. I can also reduce power and achieve the same thing of course (but that's no fun).

I think some coils will hit the primary quite often and some won't. Some coils are geared up just enough to do so and no more. Sparks start in the horizontal center of the toroid as we all know. It always starts out horizontal (or say emitting directly outward from it's origin). After the spark begins it's length increase, then it begins to bend. With higher power, it seems that initial thrust outward heads out far enough to stay away from the primary or whatever. But with just the right power, it can bend right down and then there's the primary or strike ring willing and ready to accept the connection. The spark "should" actually head upward due to heating. And at first it does, but then the fields overtake the heating affect and drive the spark downward as the spark progresses further from it's origin. Easy to see in just about everyone's spark photo's (from big coil to little coil).

As coilers start increasing power to attain longer sparks, they eventually cross the primary strike bridge. Coilers may wonder why (did they do something wrong, did tuning go south, what happened?). Well, they simply reached that threshold. It's time to boost power further to get over the hurtle (or reduce power, or even maybe change the top load height and/or size).

Take care,
Bart

David Rieben wrote:
Hi Bart,

Cameron Prince uses a flat ribbon primay design
for his primary on his big coil, too. It would have
been easier for me to employ the flat ribbon if I
had started the design with a flat ribbon primary to begin with, as "retroing" from a copper tube
design back to a flat ribbon design would pret-
ty much require a complete dismantle and reas-
sembly of the system. It's funny too, because sometimes I can hurl multiple streamers for a minute or so non-stop without hardly a single primary primary strike and then the
next 30 seconds the streamers may hit the
primary area 30% of the time! They seem to
do what they want to do ;^)

David Rieben

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