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Re: Chip's Coil

Subject: 
            Re: GNATS meeting, and harmony/synergy
       Date: 
            Wed, 19 Mar 1997 06:50:14 -0800
       From: 
            Bert Hickman <bert.hickman-at-aquila-dot-com>
Organization: 
            Stoneridge Engineering
         To: 
            Tesla List <tesla-at-pupman-dot-com>
(big snip)
> 
> Richard,
> 
> One thing that you mentioned and I forgot to mention is that Jeff and I
> tried getting the gap to work with just the primary and no secondary at
> all.  Same flaming!  This now indicates to me that the 6" secondary was
> taking energy out of the system and allowing the gap to quench.
> 
> I am going to try an experiment sometime this weekend if I get the
> chance.
> I'm going to rig a pulley in the garage and attach a line through it to
> the top of the coil.  Then while the coil is running I'll try to slowly
> raise the secondary and see where the output is the best.  I figure the
> best output will imply the "best" use of energy.
> 
> Here's another question -- If I really work on a gap system that allows
> me
> to produce a nice snappy spark on the rotary with no secondary in the
> circuit, do you think that I would then have a really excellent gap
> system
> that would Do Great Things, or would it be just an exercize?  Of course,
> if
> no one knows, I can always try the experiment too.
> 
> Chip
> 
> =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
>  Chip Atkinson
>  http://bhs.broo.k12.wv.us/homepage/chip/info.htm
>  --- Tighten it 'till it strips and back off half a turn ---
> =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

Chip,

It certainly sounds like you don't have enough of a "load" - your 4"
secondary's too small for the amount of energy you've got in the
primary. With fairly tight coupling, this usually results in the
secondary getting overvolted and showing signs of flashover. The fact
that this wasn't happening suggests that your coupling may have also
been fairly low, limiting the amount of energy you could "push" into the
coil before you stretched the gap wide enough to prevent reignition.

As to your second question, testing a rotary with no secondary will
probably be an excersize in futility, since most of the primary's
initial energy must be still be dissipated primarily in the gap. This is
similar to the non-breakout case while driving with a secondary. Since
you can't transfer any energy to the secondary, current in the primary
circuit rings at high amplitude for a longer time, causing longer arcs
and the flaming you observe. BTW, another cause of flaming is where your
tank capacitance is too low relative to the current available from your
power source. With a 0.025 uF cap, this doesn't sound like what you're
running into however.  

Safe coilin' to you!

-- Bert --