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Re: Tesla Research Possibilities
From: Malcolm Watts[SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent: Tuesday, September 16, 1997 3:04 PM
To: tesla-at-pupman-dot-com
Subject: Re: Tesla Research Possibilities
HI Pete,
> From: Pete Demoreuille[SMTP:pbd-at-cybernex-dot-net]
> Sent: Monday, September 15, 1997 7:27 PM
> To: tesla-at-pupman-dot-com
> Subject: Tesla Research Possibilities
>
> All -
> This year I have the opportunity to do independent research
> as a class in school. Being very interested in Physics, Math and
> the like, I hope to be able to do further research into the several
> Coils that I have built. I am hoping that some of you have some ideas
> that you could share with me, or could give me comments on some of the
> design ideas that I have listed below. I hope for this to be original
> research - hopefully I will be able to enter this project as a
> Westinghouse project - but it must be original and at least somewhat
> applicable to the real world - no matter how small.
>
> I was wondering about several things. Why is the accepted standard
> of turns in the 400-1200 range? Is there a rationale??
Of course. Given the typical h/d ratio of most coils, cramming too
many turns on forces the wire to be too small and the secondary losses
to increase unreasonably. You must have read my recent posts?
Why not go to one turn? Well, a TC produces ts output voltage
based on the square root of the ratio of primary to secondary
capacitances. You can in principle do this. However, the primary must
be tuned to the secondary or it won't work. I leave you to calculate:
(a) the primary inductance to maintain tune, and
(b) the primary surge impedance (the lower this is, the more your
gaps chew up, the more your caps suffer, the more primary Q suffers
as a result).
> Why hasn't
> anyone ever made a coil with many more turns, i.e. 3000+.
I reported only last week on the abysmal results I got from an 1800
turn coil. See above re wire size.
> If making
> the coil have a desirable aspect ratio is such a problem, then use a
> thinner wire, and to make higher currents possible in the coil you may
> use multiple layers wired in parallel. (and does aspect ratio really
> matter *within reason* in resonator coils or base fed coils???)
Depends how you define "within reason". You can indeed use many
layers, or litz wire etc.
> With a secondary with many more turns, wouldn't it be possible to
> greatly increase the pri/sec coupling without having to worry about
> interturn breakdown - because there are so many more turns, the
> interturn voltage rise would be bearable.
The thinner the wire, the thinner the insulation on it. Then of
course, yet again, there is the loss....
> Also, relating to efficiency. Has anyone ever tried other primary
> designs? i.e. not just flat and helical, and ones with a constant
> slope, but ones with a constantly increasing slope, in order to make
> a more desireable field and completely 'immerse' the coil in the field,
> making voltage rise occur over the entire coil - not just the bottom
> half.
Try it and see. More desirable field?
> ** many many questions coming - be warned **
> Has anyone ever done research into why the color of the sparks are what
> they are - i.e. purple when they terminate in the air, and white/blue
> when striking an object.
The difference is streamer current being higher and concentrated in a
narrow channel rather than dispersing in a spread out fashion. The
resonator loses its energy very quickly when striking to ground.
> I know that glass is supposed to give purple
> spindly sparks - but why?? the rate it discharges at? its higher
> dialectric constant??
Nope, discharge rate is primarily dependent on plate geometry and
method of connection (e.g. extended foil vs end-end. Sort of; the
higher the dielectric constant _in general_, the higher the losses
(sort of equivalent to hysteresis loss in a magnetic core). Of course
if the primary components are merrily dissipating most of the energy,
not much is left for the output.
> What do caps of Barium whateveritis do
to > spark color?? why are caps with a higher dialectric constant
less
> efficent when operating at RF?? why do secondary coil forms with
> a thicker wall cause more RF loss??
See answer immediately above.
> Wow. I think I exhaused my questions for the moment -
>
> THANKS ALOT FOR ANY INPUT!
>
> Pete Demoreuille, Delbarton School
>
> ps: one more - what kind of amperage is entering the coil from ground?
> And exactly why does the amperage convert from AMPS at the bottom
> of the coil to potential at the top?? The secondary is for the most
> part DC? shouldn't current be constant??
> (last one i promise) :)
The secondary is wired as a resonator, not a lumped inductor.
It is inductive at the base, capacitive at the top. When it is
not producing a hard spark from the top end, virtually no current
flows in that end as energy is distributed along its length.
There is a phase shift of 90 degrees from bottom to top. See Greg
Leyh's previous posts on measurements of his coil. All you ever
wanted to know and more is buried in 25MB+ of list archives.
Malcolm