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resonances....
>Subj: Re: Any Reason For This???
>> While firing my 6" coil the other night I decided
>> to put my earlier 4" on a chair so that the top bushing
>> was about 2' away from the 6" coils torroid just
>> to see what would happen. I expected the arcs
>> to strike the top terminal of the 4" and who knows
>> maybe what else? I was suprised that rather than
>> hit the top terminal the arc took a direct path
>> about a third way down the 4" coil puncturing a
>> hole through the Behr build 50 and stayed there
>> like it was glued solidly. Anyone have a idea why
>> this arc missed a brass terminal that was about 6"
>> closer and took the hard road through epoxy and
>> formvar to find happieness?
Could be the basic cussedness of inanimate objects. Or, as the
biologists say:
Under carefully controlled conditions of temperature, humidity
and nutrient mix, the organism will do just what it
D*** well pleases.
(In this case, once 'struck', the cloud of 'cruft' and ions
might well make it stay 'there'. 'There' COULD be an a accident,
but the mention of '1/3 down from the top' is intriguing. Consider
a coil (or object) resonating at 3/4 mode:
Peak at top
NULL (of voltage) 1/4 wave down
anti peak 1/4 wave futher.
null (of voltage) 1/4 wave further (base).
Izzis what happened? dunno. But it fits. this would lead to
a virtual 'ground (low voltage) point 1/3 the way down....
Was it a metal chair? This would provide another virtual ground
at the 'base' of the unpowered coil, by stray capacitance.
There are a lot of ASSumptions in my guesswork.
>Glenn,
>Regardless of whether you had the base of the free coil grounded or not,
>it will resonate at its characterisitc wavelegth as a 1/4, 1/2, and or
>3/4 wavelengths.
Any distributed resonator (wire, coil) will resonate at frequencies
every 1/4 wave from 1/4 on up. Its VERY striking when viewed with
a tracking generator/spectrum analyzer. The 1/2 wave, full wave,
3/2, etc will tend to predominate with both ends ungrounded... One
sees the chain of resonances, marching up at f, 2f, 3f, 4f, etc....
In practical coiling, the higher modes are likely to be lost in
losses in caps, and, in anay case, to be avoided, as the rob energy
from the (usual) fundamental resonance at 1/4 wave.
>Where the 6" coil's spark hit was a nodal point on the 4" where a high
>voltage appeared out of phase with the 6" coil's arc. The two added
>together and a nice long arc which stayed connected was the result. The
>arcs found one another at the ideal summing point for the two systems.
Or, perhaps, a virtual ground....
>Richard Hull, TCBOR
regards
dwp