Re: Tesla Coil Blunderbusses

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-uswest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi all,
        This morning after doing a bit of thinking about this result, 
I had an idea which I would like to put to the list for scrutiny and  
testing. I was spurred by Dr Cadd raising the subject and also John's 
reply below:

On 10 Apr 01, at 12:25, Tesla list wrote:

> Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>"
> <FutureT-at-aol-dot-com>
> 
> In a message dated 4/9/01 8:54:54 PM Eastern Daylight Time,
> tesla-at-pupman-dot-com writes:
> 
> > >I have seen exactly that effect. I started with a smoothly running
> >  >coil, then tuned the primary down to enhance the lower sideband
> >  >response. Operation went from smooth to erratic but the sparks
> >  >increased considerably in length (about 20% from memory).
> >  >
> >  >Regards,
> >  >malcolm
> 
> Malcolm, all,
> 
> Thanks to all who have responded.  It turns out I was aware of
> this effect, but wasn't thinking.  I wonder why the operation became
> erratic at the new tune point?  
> 
> John Freau

There are two "mysteries" to be explained here - the longer sparks 
and the erratic gap operation. Here is a possible answer to both. It 
can be put to the test by capturing "before and after" waveforms on 
the storage scope - I plead lack of time and sleep to do it right now 
but I certainly will in the course of time, especially if no-one else 
takes up the challenge.

      Here goes: we know that Ep was the same in both cases so we can 
reasonably assume that in both cases, Es was roughly the same. Hence, 
spark length cannot be explained by differences in energy.
     Suppose the tuning difference results in the secondary being 
unable to backload to the primary as effectively as it would if the 
tuning of the circuits was identical. Two things would result: energy 
would be bottled up in the secondary for longer and this amounts to 
an earlier gap quench by proxy. We know that the shorted gap at 
firing time assists the power supply in storing energy in its 
leakage/ballast inductance and there is a time dependence in there. 
Admittedly the time difference is short but it may be significant 
(e.g. a quench after 1 beat instead of 3). So a marginally set gap 
might have difficulty refiring due to less resonant rise in the power 
supply due to stored energy. And the secondary rings for longer 
without an interbeat period of quietness in between.
      Does this make any sense? This might be a useful hint at a way 
of increasing gap quench effectiveness no matter what method is 
currently employed in a system. And it may be less lossy than forcing 
a jet of air to blow the primary spark our as well. I think this 
should be tested. I hate unknowns.

Regards,
malcolm