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Re: [TCML] Rotory STATIC Gap

Hi Gary,

I believe what Scot is referring to is that he has a conductive ring that electrically joins the "flying" electrodes together and that his "stationary" electrodes are placed 180 degrees apart on opposite ends of the rotary disc. The stationary electrodes are properly jumping to the flying electrodes as a pair will line up with a presentation. Obviously, the total gap spacing at the presentations is on the order of a few .01", assuming he has his clearances tight enough to allow reasonably close flying/sta- tic electrode alignment without collision. However, it seems when the flying electrodes are NOT aligned that the primary circuit voltage is reaching high enough amplitudes that the 2.2" clearance between the stationary electrode surfaces and the surface of the conductive copper ring, in between the flying electrode presentation alignment,
is being briged by the primary circuit voltage.

I believe Scot is driving his coil with two seriesed output 14.4 kV pigs that are overdriven with up to 280 volts input into the 240 volt side for over 30 kV feeding the primary circuit. Depending on the electrodes geometry, it would likely take a pretty nasty primary circuit voltage to start jumping well over 2" at only around ~25 kV input, so there must be some resonant voltage rise issues going on ;^0 Since his stationary electrodes are jumping the full 2.2" to the copper ring that connects his flying electrodes when he turns his variac up past 75 to 80%, then at this point, his "rotary gap" does effectively become a "static gap"
since it would bridge the maximum spacing of 2.2" whether or not the rotary
disc is rotating. Even for a ~30 kV primary circuit input voltage, 2.2" does
seem rather extreme.

Scot is also proposing placement of the conductive ring that electrically joins the flying electrodes on the opposite side of the rotary disc from the two sta- tionary electrodes, as opposed to the same side in his currcent setup, to further seperate the concustive ring of the disc from the stationary electrodes by at least the thickness of the rotary disc itself. However, I would think that if the primary circuit voltage is jumping the 2.2" clearance at 75% on the variac knob, it would probably just jump the extra 1/2" around the edge of the disc once the variac knob
is turned on up to 90% or more.

Wow, Scot, I didn't know you had this much voltage rise in your primary circuit! I'd have to agree with Gary here in that I'm surprised that your coil fired flawless-
ly for 9 years without a breakdown running in this fashion.


----- Original Message ----- From: "Lau, Gary" <Gary.Lau@xxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Thursday, October 23, 2008 2:51 PM
Subject: RE: [TCML] Rotory STATIC Gap

Hi Scot,

If you're seeing the spark gap jump anything remotely like 2.2 inches, your coil components (cap and NST?) are not long for this world. That length indicates that the cap is charging to a MUCH too high voltage. Any rotary gap, sync or not, needs to have a properly spaced static gap in parallel with it, so that it fires before the voltage gets out of hand and things start going poof.

I'm having trouble visualizing your setup, so it would help a huge amount if you could post some photos.

Also, please be consistent in the use of the word "static". Your RSG has rotating electrodes, and it has stationary electrodes. When you say that it has static electrodes, or operating in static mode, I'm not sure what you're referring to.

Regards, Gary Lau

-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
Behalf Of bunnykiller
Sent: Thursday, October 23, 2008 2:09 PM
To: Tesla Coil Mailing List
Subject: [TCML] Rotory STATIC Gap

Hey All....

I was looking at my spark gap ( SRSG) and noticed that the timing must
have been off or the primary circuit voltage had jumped up quite a bit
and started arcing before the electrodes were in position.  The gap is
designed with 4 flying electrodes and 2 static, since I couldnt place
the statics on each sides of the disc, I had to put them on one side of
the disc ( away from the motor). To achieve conduction, I had to place a
copper ring around the periphery of the disc to conduct from one
electrode to the next. (This was done to keep the stationary electrodes
from arcing to the motor.)

This configuration allowed the primary circuit to charge to voltages (
well as far as the distance from the stationary gap distance was from
the copper ring ( 2.2" total gap width)) which would then jump the 2.2"
length to conduct.  As the electrodes would proceed into the stationary
region, it would ( im supposing now) lower the gap voltage for
conduction and eventually quench.

So in effect, the gap was firing in "static" mode and then finished off
in rotory mode.  Guess I need to get rid of the copper ring to have a
true SRSG.... ;)

At lower input voltages to the piggie, the gap works fine ( as its
supposed to) but once past 75-80% on the variac, the "static" mode appears.

Need to design a better SRSG that can fend off 40KV+ and not attack my

Scot D

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