Re: [TCML] SRSG "sputter"

[Gary Lau <glau1024@xxxxxxxxx>]

Hi Joe,

The sharp, cracking sound you describe sounds like something equivalent to a
safety gap firing due to overvoltage and bad phasing - something that
definitely needs fixing.  If it's not in the safety gap itself, you'll need
another pair of eyes at a different vantage point to spot the source of the
discharges.  For the arcs at the outer edge of the primary - are they
between the primary and strike rail?  But the location of the sounds is
secondary to the underlying problem of why you're getting an over-voltage
breakdown in the first place.

Perhaps the phase of the gap is just very far from where it should be and
beyond the range of the Freau adjuster?  Maybe try rotating the motor or
disk 45 degrees?  What you should see is that as the adjuster Variac
inductance increases and the phase moves later in time, the spark length
grows until it abruptly goes to pot and the safety gap fires.  BTW, I think
the word "dwell" has no place in this discussion; dwell refers to the amount
of time that contacts are closed, usually in the context of automotive
ignition systems.  We're varying the phase of the gap firing, not the
duration of the firing.

Just to be certain - your motor is 1800RPM?  I don't think that
primary/secondary tuning is a factor in this problem.  I don't think a small
angular error in the disk electrodes would do this either.

I didn't understand what you saw when you adjusted the phase - "that just
pretty much lengthens or grows the signal intensity".  Are you certain that
your motor is synchronous and that the adjuster is working?  Have you tried
taping a magnet to the shaft and scoping a pickup coil to determine the
range of adjustment?  It's easy to put a too-heavy rotor assembly on a small
motor and have it unable to run synchronously.

Regards, Gary Lau
MA, USA





On Wed, Jul 7, 2010 at 10:50 PM, Joe Mastroianni <joe@xxxxxxxxxxxxxx> wrote:

> Hi All,
> Ok, while I'm awaiting my parts from McMaster Carr to do my next version of
> the SRSG, and propeller gap, I'm still fiddling with this little 4" wheel I
> have.
>
> What I'm noticing is that at below  1/2 voltage on the variac, the gap is
> happily firing, and things are calm and sparky.  When I go to about 2/3
> power, I start getting a sharp crackling from the area of the gap itself.
>  Sometimes the safety gap on the SRSG fires, and sometimes it doesn't - but
> if I go even higher on the voltage, my Terry Filter safety gap goes off so I
> shut down.  Sometimes, the none of the gaps fire and I get a quick arc in
> the vicinity of the outer turns of the primary.
>
> For grins I turned on the fan again I had blowing on the gap, and that
> seems to have no effect, positively or negatively.   I tried adjusting the
> gap itself between the rotating rods and the stationary rods, and smaller
> gap seems to be better than larger gap, but I still get the "sputtering".
>
> I have tried adjusting the dwell with the Freau adjuster, but that just
> pretty much lengthens or grows the signal intensity, and as the voltage gets
> up there, the sputtering starts again.
>
> Definitely cannot run at full power.
>
> I have tried tightening down on the collars that hold fast the rotating
> electrodes by squeezing them with a vice grip to assure contact with the
> copper ring on the back and then tightening the set screws, but there seems
> to be no effect there.
>
> I'm wondering if I could have a "timing" issue in that the electrodes may
> not be precisely 90 degrees apart - perhaps a fraction or a degree off,
> depending.  My protractor method could have been imprecise.
>
> ANy thoughts would be appreciated.  Or I wonder if my tuning of the contact
> to the primary is still off by some amount of a full turn....
>
> Cheers,
> Joe_______________________________________________
> Tesla mailing list
> Tesla@xxxxxxxxxx
> http://www.pupman.com/mailman/listinfo/tesla
>
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