Re: Mysterious result....

To: tesla-at-pupman-dot-com
Subject: Re: Mysterious result....
From: Richard Hull <hullr-at-whitlock-dot-com>
Date: Fri, 15 Nov 1996 10:11:30 -0800
Tesla List wrote:
> 
> >From DavidF4797-at-aol-dot-comThu Nov 14 22:17:01 1996
> Date: Thu, 14 Nov 1996 12:37:09 -0500
> From: DavidF4797-at-aol-dot-com
> To: tesla-at-pupman-dot-com
> Subject: Mysterious result....
> 
> I have been running a 4.5in O.D. by 24in coil now for some time.  My primary
> had been designed for a larger coil  its' dimensions are: 10in I.D., 30in
> O.D. 12 turns 3/8 copper tube tapped at 10 turns, saucer shaped helix 30
> degrees incline.  Cap value of aprox .01mf.  My supply is a 15kv 60ma neon
> and I was running a series gap of 8 lengths copper pipe with 1/16in spacing
> for a total of  1/2in gap.  After repeated trials I was never able to get the
> gap to fire consistently using more that 6 gaps (3/8in total).    At seven
> gaps, the the fireing would be intermittent or would cease altogether after a
> time.  With 8 gaps (1/3in) the gaps would not fire at all  even with full
> turn-on surge (no variac)
> 
> I was always curious as to why this was the case.  It would seem to me that a
> 1/2in gap shouldn't be to large for a 15kv/60 neon to bridge but I never
> pursued the details since the coil seemed to run just fine at 3/8in and I
> suspected that it would be gentler on my cap anyway.
> 
> Here's the strange part.  I recently switched to a smaller primary: 6in I.D.
> - 18in O.D. with 12 turns 3/8 copper tube banked at 45 degrees.  This
> produced much greater output - due to increased coupling characteristics I
> would guess.  I also found that I could now run at the full 8 gap (1/2in)
> setting on my gaps without any intermittency noticeable.  The local expert
> was stumped as to why this might be the case.
> 
> The only potential explanation I could come up with is that due to the
> increase in coupling, the back EMF pulse (as the secondary waveform
> collapses) is sufficient to bridge the extra gaps and keep the gap system
> fireing when it otherwise would not (was not).
> 
> Any ideas out there?
> 
> Thanks in advance:
> 
> -DavidF-


David,

The back emf would not be the explaination at all, as the gap must break 
down the first time inorder to give you the back emf.  So that one's out.
>From what you have given in the post there is no ready explaination that 
comes to mind, assuming nothing in the gaps have changed and you are 
using the same transformer and hookup.  A primary change would have zero 
impact on the initial firning of the gap.

Richard Hull, TCBOR