sparks question

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

Original poster: "Peter Lawrence by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Peter.Lawrence-at-Sun-dot-com>


OK, here is a "real" question for you all...

I get "really great" sparks with my TC when I use a large diameter primary
and raise the secondary. The difference between really great and
not-so great is a few long sparks going vertical off my sphere verses lots of
short sparks going vertical plus lots of short horizontal sparks off my toroid.

                         -
                       /   \                 2" sphere
                       \   /
                         |
                         |
                 -       |       -
               /   \ ____|_____/   \          2x8" toroid
               \   /  |     |  \   /
                 -    |     |    -
                      |     |
                      |     |
                      |     |                 3.5x12" secondary form
                      |     |
                      |     |
                      |     |
                      |     |
                      |     |
              ========================        5.5-11.5" primary


I really prefere the "few long vertical sparks" mode of operation, but I
do not have any explanation for what causes that.

I have three different diameter primaries, each requiring a different
raising of the seconary to achieve "great sparks", here are the stats
in case you want to try a theory

Sphere = 2" diam, center is 4" above center of toroid (7/8" cu pipe between)
Toroid = 2x8" diam, bottom of toroid 1/4" above top turn of sec winding
secondary = 2000 turns #38 wire Quad coated, 3.5 diam x 11" winding length,
            nominal start height = 0.75", finish height = 11.75"
            
A)
	primary = 14.5 turns (#12 wire, 50% space wound) 8.86" ID to 13.5 OD
		  nominal start height = 0.3", finish height = 0.5"
	riser = 0.5" for "best" sparks,  K (ACMI) = 0.0988 (1/10)
	
B)
	primary = 15.5 turns (#14 wire, 50% space wound) 7.875" ID to 11.75 OD
		nominal start height = 0.3", finish height = 0.5"
	riser = 1.0" for "best" sparks,   K (ACMI) = 0.0908  (1/11)
	
C)
	primary = 18.5 turns (#14 wire, 50% space wound) 5.375" ID to 10" OD
		nominal start height = 0.25", finish height = 0.4"
	riser = 1.5" for "best" sparks,   K (ACMI) = 0.0823  (1/12)


So "coupling" is not a complete answere, because each of these requires a
different value. What then could be the cause.

I'm trying to produce a design that fits in 12" diam primary and without any
riser for my secondary so that it is "compact", but I'm not having any success.


Peter Lawrence.


(ps, Quad coated wire, plus half a can of insulating varnish, have solved my
racing sparks problems)

(pps, a fan from a MO makes it possible to run for long times with my static
gap without ever getting so hot that it starts power arcing, but does not seem
to affect the quality of spark I've described above)