Tuning .....

To: tesla-at-pupman-dot-com
Subject: Tuning .....
From: Mark Finnis <mefinnis-at-medicine.adelaide.edu.au> (by way of terryf-at-verinet-dot-com)
Date: Thu, 27 Aug 1998 17:28:30 -0600
Approved: terryf-at-verinet-dot-com

From: Mark Finnis <mefinnis-at-medicine.adelaide.edu.au>

Principally for the novices .... like me ;-)

A few weeks back I posted my "first (almost) light" pictures ....

	http://www.cobweb-dot-com.au/~dkfinnis/images/second_light_1.jpg

which were encouraging but less than I would have expected for a 6" coil
and 15 kV at 120 mA (NSTs).

So for the benefit of other beginners/novices these were the changes:

1.  At the suggestion of Malcolm Watts, changed the copper-plated steel
tube primary for solid copper 1/4" tube.  Small increase in spark distance,
moderate increase in intensity.

2.  Built a new spark gap, as discovered the modified large
copper-tube/bolt-electrode gap had destroyed itself.  This time spent some
money & bought tungsten electrodes from a TIG welder.  Only three pairs as
this is all they had in stock (can always add more later!).  Added these to
decent heat-sinking and produced current gap:

	http://www.cobweb-dot-com.au/~dkfinnis/images/sparkgap_mk5_2.jpg

This produced a *marked* improvement in length and intensity, about 6".

3.  Read various comments on "coupling" on the list, and the relation of
this to quenching, so thought I'd "de-couple" the secondary, as I had set
it initially with the secondary base turn = height of primary.  I built the
coil so changing this was easy to do - moved up 1".  Amazing improvement in
spark length.  Previous best to earthed ball about 34", now out to 44" with
regular strikes and previously ignored pieces of the pergola became very
attractive .... 

	http://www.cobweb-dot-com.au/~dkfinnis/images/run5_01.jpg
	http://www.cobweb-dot-com.au/~dkfinnis/images/run5_02.jpg

	gettin' warmer ;-)

While I had read small differences like this could have a dramatic impact,
I have to confess I didn't really believe it.  So, if your a beginner &
building a coil - make it adjustable !!!!


Two more improvements planned:

1.  Bigger toroid.  (actually arrived yesterday but got dented in transit,
so is having to go back .... $%%^#-at-$&-at-#^&&& ...... damn! )

2.  Flat plat capacitor.  Current cap is rolled P/E with "end-connections"
and a long roll-length of 3.5m.  Still for first pair of home-made caps
they have endured a heap of punishment !


Cheers,

Mark

http://www.cobweb-dot-com.au/~dkfinnis