Re: ASRSG question

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "David Rieben" <drieben@xxxxxxxxxxxxxxx>

John,
You wrote:

> David,
> You mentioned setting the electrodes as close as possible.
> How close was that?  In some cases for small coils I've had to run my
> electrodes almost touching (just a few thousands of an inch).
> I'm not recommending that for your case however because
> if tungsten runs too close, the electrodes tend to break off
> if they strike each other.

Thanks for your response on this issue. First of all,
I set the electrodes within 1/16" of each other so that
x 4 means that there could not have been more than a
1/4" total gap spacing. Just under 1/16" is about as close
as I can safely run my homemade RSG w/out danger of
electrode collision. I was running with a 14.4 kV pig so
the voltage should have been high enough to reliably
fire this gap. Actually I made a mistake in describing
my rotay electrodes in my first post. I said that they
were 1/2" dia x 2 1/2" long. The correct measurement for the rotary 
electrodes is 3/8" dia x 2 1/2" long. All
of the other measurements were correct.
> Maybe the problem is that you are only using
> two electrodes on your rotor.  This requires a very high
> motor speed to get a high break-rate.  These speeds
> may make it difficult for the rotary to fire if the electrodes
> are narrow in diameter.  Lower speeds may
> give erratic firing as the system semi-phases in with the
> input ac power 60Hz waveform.  ASRG users often use
> 8 or 10 electrodes on their rotors, and run at a lower RPM.
> I remember Bob Svangren once mentioning that he tried
> using 6 spinning electrodes instead of the normal 8, and
> his system failed to work at all.  Perhaps it gave him a too-low
> breakrate.

No, I'm using 8 rotary electrodes driven on a 11 1/2" diameter
x 1/2" electrical grade fiberglass disc. The motor is a variable
speed 0 - 130 VDC, 2.5 HP treadmill duty motor that is rated
at 3500 rpm.

> Nevertheless folks such as Richard Hull often used a series
> multiple static gap in series with their rotary and still didn't
> have a problem despite the wider total gap spacing.  Are you
> using a static gap in series with your rotary?  If such is used
> and has too-wide gaps it will cause a problem.

No again, I am using no seriesed static gaps in my setup.

> Wider electrodes (such as 1/2" dia) will tend to fire more
> reliably because there's more time available for firing during
> the mechanical dwell time.  Usually 14.4kV doesn't give a
> problem.  Folks who use 7.2kV may need to set their
> gaps somewhat close.

Like I said, My rotary electrodes are 3/8" in diameter and my stationary 
electrodes are 1/2" in diameter. Dr. Res. has already addressed the 
electrode size issue in that "they"  use
1/2" diameter rotaries and 1" diameter stationaries but I think that this 
is more due to the expected rigors of several hours
of operation a day for years at a time. Most hobby level\coilers
use SG electrodes more in line with the size(s) that I'm using
for the power levels that we're talking about. From the 69 meg, 7 minute 
video of Kevin  Eldrege's Biggg Coil, it looks like
even he dosen't use SG electrodes much more robust than what
I am using. Of course his electrodes definitely do show signs
of wear, too :^)

> The particular capacitor value that's used along with the
> ballasting inductance value also affects the firing voltage
> and can be a factor in gap firing.

I first tried .2 uFD, or both of my .1 ufd pulse caps paralleled,
then I scaled back to a single pulse cap for .1 uFD. Still the same
problem, although I think it may have "tried" fire a little bit more
frequently this way than with .2 uFd. Neither way was acceptable,
though and finally burned out the 1kv,50 amp FWB rectifier for
supplying DC voltage from the AC mains for the DC motor. That
must have been  a  pretty significant kickback surge considering that the 
RSG motor only draws around 2.5 to 3 amps once its rotational speed has 
stabilized. It's max, full-load amperage rating is 17
amps, I believe. BTW, I was using line filters, both at the control panel
and at the hookup of the DC motor itself, but it still smoked my 1kV,
50 amp FWB! The pig and the main power control 1256 variacs survived
though ;^) The resultant short circuit did cause a "sticky" spot on the 
smaller motor speed control variac, but it also survived.

> So anyway I've presented some ideas for consideration above.
> I'm not sure though exactly what's happening in your system.
> Regarding the 180 degree electrode positions, such a gap
> may run cooler, and make it harder for the electrodes to fire
> maybe.

Perhaps, but in my case, it wasn't even firing enough for the
gap temperature to make any difference. I've simply removed the second pair 
of of stationary electrodes and now there is only
ONE pair of stationary electrodes on just ONE side of the motor.
I haven't had a chance to pull it out and test fire it yet but this solved
this particular problem in the past :^) Keeping my fingers crossed...

> Cheers,
> John Freau

 David Rieben


---- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Saturday, April 02, 2005 12:14 PM
Subject: Re: ASRSG question


> Original poster: FutureT@xxxxxxx