Re: How many STSG's in service?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jason Petrou by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jasonp-at-btinternet-dot-com>

John,

Good luck with your test - forward me the results if you will. It will be
interesting to see whether or not your results are similar to mine. How are
you planning on feeding pulses to the ignition coil? Are you going to use a
zero crossing chip run off a phase shifter and a FET setup or the good old
mechanical way like me :)

> I obtain the same results with a 9" rotor, 7" rotor, and 5" rotor
> on my TT-42 TC.  In a properly working system, the gap arc
> should quench while the electrodes are still aligned.  This occurs
> because the energy has dissipated.
At 200 breaks, a power arc seems to form on the first break, rather than the
second break, i.e. as the sine curve is still rising on the first break (at
45 degrees). I am not sure why this is, but I can hazard a guess. When the
sparkgap fires and creates a path for the ionised air to follow it also
allows the rising voltage on the sine curve to continue a power arc after
the cap is discharged. On the second firing at 135 degrees the voltage from
the AC line is not high enough to continue a mians power arc, but the cap is
still charged from the peak of the AC line.
    This notices on my coil because I am using a resonant cap - for whatever
reason the first firing seems to power arc more - possibly something to do
with the cap resonant charging as opposed to DC charging.

> If the rotor is too small,
> the power too great, the motor too slow, the cap too small, or
> the ballasting not correct, then the gap can "re-fire" while the
> electrodes are still aligned, causing heating of the electrodes,
> arc-trailing, and inefficient operation.  Often these problems
> can be eliminated by rounding the tips of the electrodes some,
> especially if they are thick or wide.
Good point - I rounded the tips of my electrodes to try to conpensate for
it, and it seemed to reduce both jitter and power arcing.

If anyone was interested the way that I tested this was to put a piece of
paper around the disc, and the the bit of paper after the first contacts
burnt, but never after the second.  Not very advanced, but it worked :)

As I say John, please share your findings with us.

Best regards,
Jason