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Re: [TCML] 6" Coil Sparks too short

On Thu, 26 Feb 2015 08:00:32 -0800
Kuba Anglin <kubaanglin@xxxxxxxxx> wrote:

> Brandon, you say that I should be running 5-6 times my current rsg
> setup. That seems very significant. What should my bps be on this
> coil? Since this is my first rsg coil, I am not incredibly familiar
> with rotary spark gap operation. If I simply added more electrodes to
> my disc and tested the coil, would that be a good place to start?
> -Kuba

> 2) .80 BPS is way too slow.

> 3) Running NSTs in asynchronous mode is one of the best ways to kill
> them.

> Matt D

Hi Kuba

When running NSTs you should be running at some multiple of line
frequency, 120bps or 240 bps in synchronous mode. As Matt has said,
running asynchronous is a great way to ruin your NSTs.

Also in the spark gap picture I do not see a safety gap or a "Terry
filter" both of which would help to prolong the life of your

I see in the spark gap picture that the motor is a nice one, easy
enough to disassemble for modification to synchronous operation. If you
mill (or grind) four flats on the stator then it will be able to lock
to the line frequency and run at 1800 RPM which with four electrodes on
the spark gap rotor will produce 120bps (recommended). It appears you
have "saddles" on the motor mount which will allow a rough adjustment
of spark gap timing. The addition of a "John Frau phase shifter" will
allow for "real time" phase adjustment.

I would also recommend a safety gap across the rotary spark gap to
catch missed firings, and yes, also a "Terry filter" to help protect
the NSTs from over voltage.

Another thing that is hard to tell from the picture, but the spark gap
rotor appears to be clear. Hope you are not using acrylic or
polycarbonate for that:-)

One more thing I see in the spark gap picture is a lot of alligator
clips. This is something that could also be contributing to poor

Best of luck in your endeavor
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