Re: reducing spark gap losses?

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

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <FutureT-at-aol-dot-com>

In a message dated 7/30/02 8:37:55 AM Eastern Daylight Time, tesla-at-pupman-dot-com
writes:


>
> A few days ago there was a post about a clever trick (can't remember
> their name...) using smaller diameter litz wire for the secondary and 
> increasing the number of turns on the primary.  Which then reduces spark gap 
> losses.  Also having the added affect of more turns on the primary and 
> reduced voltage differential between each turn (from one of terry's 
> experiments) allowing for a tighter spaced primary.  (is that even 
> desirable?)



Larry,

I use a many turns on primary and secondary to raise the 
primary surge impedance and reduce gap losses in that way.
This explanation was first given by Malcolm Watts, for the 
greater efficiency that I saw in such designs.

I talk about this some, at my website:

  http://hometown.aol-dot-com/futuret/page3.html


>
> anyway... i ramble.
> Question: compare single point static gap to multipoint gap.  i would like 
> to assume that multipoint gaps loose less energy. would i be correct?



Some say the opposite.  In any case, a better or worse result won't
necessarily decide that.  Heating and quenching aspects can skew
the results in favor of the multigap.


>
> a related question.  I have a vacuum gap, single point.  when vacuum is not 
> running and gap is relatively small: the gap runs well between lets say 
> 30-50%, but over that, it behaves like it is 'strained,' and spark output 
> diminishes by upto half.  return the variac back down to the 30-50% mark and 
> it returns to normal operation.  would this be caused by the gap not being 
> quenched or perhaps something else?



Probably caused by poor quenching and/or gap overheating.  Gap
overheating lets the gap fire at a lower voltage, thereby reducing
the bang size.  It also can hurt the quenching by keeping lots of
ions around.


>
> i will probably make a 4 point vacuum gap to test that the multi point gap 
> will function better. the gap im using now is probably overkill as I'm using 
> 1" diameter contacts with multiple holes drilled in them.



4 point gaps tend to run cooler, and quench better than single gaps,
but may have higher losses, but still often give better results.  A
single gap can work well if enough vacuum or pressure and airflow
is used.  Pressure is theoretically better than vacuum, because
the pressurized air permits a shorter gap spacing, giving lower
losses.  I'm assuming you don't mean a true sealed vacuum
chamber, evacuated of air, (hard vacuum).

Cheers,
John


>
> larry d.