Steve,
Well I can agree with what you're saying there. I usually consider a long enough secondary as a necessary "given" when building a coil.
But assuming a large enough secondary, a wide range of toroid sizes can be used and will work with varying results. For this reason I tend to focus more on the toroid size than the secondary size. The interaction of toroid size, bang size, and break rate seems like an interesting issue to me, as I know it is to you also.
Cheers, John
So, IMO, the spark output is limited by-
-the toroid size -the clearance between toroid and strike rail -the resonator length
I reckon a reasonable limit for spark length is about three times whichever of the above dimensions is smallest. (for the toroid I guess "size" would be the major diameter?)
This is based on empirical observation so is open to debate.
Steve Conner