I did some tests with my sync gap TC to compare various break-rates,
toroid types, etc.

Test 1.   The TC was still set up with the 6" by 23" secondary, and the
.0147uF cap from previous tests.  I installed one of my new 4" by 13"
spun aluminum toroids, to compare and observe breakout 
characteristics.  Because of the smooth surface, breakout was
delayed until a higher variac setting.  The sparks did not emit from
the toroid seam, but rather drifted all over the toroid surface, jumping
across the seam at times.  At low break rates (350BPS), multiple
streamers formed.  At higher break rates (550BPS), there was 
sometimes one, sometimes two streamers.  At even higher break
rates around 800BPS, the streamer remained coalesced into one
streamer.  In all cases the streamers were about the same length,
but the low break-rate streamers were probably longer.  In all cases
the streamers had good action and gave an impressive display.  The
input power was about 1500 watts, and spark length was about 48"
or so.

Test 2.   I installed the 4" by 23" secondary, and the .007uF cap, and
the 4" by 23" secondary, and redid the tests at various break-rates. 
Although the power input was lower, the sparks looked similar to
those in test 1.

Test 3.   The sync rotary gap was installed and the coil fired up.  The
sparks were not able to break out of the 4" by 13" toroid.  I then
re-installed the original 5" by 20" dryer duct toroid, and sparks broke
out but were quite weak.  It seems that what was happening is that
when I changed from one potential transformer to two, (from a previous
test), it changed the ballasting needs, and my ballast no longer had
enough range.  I added more metal to the core, to increase the
inductance, and the spark improved, but is still weaker than normal.
I should get 42" sparks at 620 watts, but I'm only getting about 38".
I will try adding more metal to the ballast, and will optimize the sync
gap phase better, and see if I can get back the 42" spark capability.
If anything, it should be better now with the two potential transformers.
I will then re-test using the 4" by 13" toroid and see if the sparks can
break out with the sync gap at 620 watts.  I did not test this toroid 
with the sync gap at higher powers using the .0147uF cap.

These tests suggest that spark break out from a smooth toroid
depends not only on voltage but on the break rate.  A higher break
rate must ionize more air near the toroid, and reduce the voltage
hold-off capabilities of the toroid.  This effect is probably nothing new
to those who have compared smooth and corregated terminals, but
I have not had access to larger smooth terminals before this time.
However, the sparks might break out of the 4" by 13" toroid now that
I've improved the ballast somewhat.  I didn't go back and re-test yet.  

Tests will continue.

I am now manufacturing these beautiful spun toroids, and I will soon
be making them available to other coilers at about half the normal
price for a commercially spun toroid.  Samples of these types of
spun toroids can be seen at my webpage at:

   <  http://members.aol-dot-com/FutureT/index.html   >

John Freau