Big sparks from ignition-coil powered TC?

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

Original poster: "Jolyon Vater Cox by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jolyon-at-vatercox.freeserve.co.uk>


I have built a TC which uses an ignition coil with electronic breaker to
provide HVDC to charge the primary capacitor via a rectifier. Having read that
ignition coil-powered TCs can deliver up to 6" or so of spark and in view of
the equation for spark length (inches=1.7 * sqrt(input Watts)) it would be to
know how to achieve such performance in practice.

The primary is a flat spiral with minimum radius of 1.5"and 

0.375 pitch between turns tapped at 9.75 turns will have an inductance of 

15.75243456uH, which in conjunction with a 17.22nF capacitor will resonate at
305.58337 kHz. The secondary is a coil with diameter of 2.8946", height 10 7/8"
comprising 880 turns of wire (inductance 13706.565uH and Medhurst capacitance
4.4850625 pF)with 25" bicycle wheel as toroid (capacitance 15.050964 pF); with
the present arrangement am getting 6" hot blue sparks to a grounded wire.

However the 25" wheel is enormous and the capacitor takes about 1 second to
charge between the gap firing; that is, the TC is producing 1 "shot" per second
and operating in almost a "single-shot" mode. I surmise that with more turns on
the primary it should be possible tune it to the secondary frequency with a
smaller primary cap but at the expense of less energy per "bang"possibly
resulting in shorter spark length -is this likely to be an unavoidable
sacrifice given the constraints of