Re: [TCML] SRSG "sputter"

[Gary Lau <glau1024@xxxxxxxxx>]

One more thought on the location of the arcing.  Your copper ring is on the
back-side of the garolite disk.  It looks like it would be difficult to see
a breakdown between the copper ring and the motor shaft, but as your
garolite disk turned out smaller than planned, it sounds like the clearance
between the ring and motor shaft/arbor could be less than adequate.  Arcs
tend to travel over much greater surface-distances (surface tracking) than
in free air.  Having a primary bang discharge through the motor is REALLY
bad for the motor!

Regards, Gary Lau
MA, USA

On Thu, Jul 8, 2010 at 8:49 AM, Gary Lau <glau1024@xxxxxxxxx> wrote:

> 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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