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Please Help



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From:  Malcolm Watts [SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent:  Monday, March 23, 1998 3:17 PM
To:  Tesla List
Subject:  Re: Please Help

Hi Scott,
          Thanks for your kind endorsement. I don't recall us trying 
to sort the problems out offlist.

> From:  Scott Hayward [SMTP:smash-at-eisa-dot-net.au]
> Sent:  Sunday, March 22, 1998 10:35 PM
> To:  tesla-at-pupman-dot-com
> Subject:  Please Help
> 
> After my first coil flopped a built another one using a lot of help from
> Malcom Watts (Thanks!).  But I tried it this weekend and it didnt work :(
> These are the specs:
> Primary coil-7turns of 0.25" copper pipe spaced aprrox 0.25" inner dia. 6.2
> outer dia. unknown

Even I can guess at what it must be if your dimensions are correct. 
About 17" ?   I calculate Lp to be about 15uH.

> Secondary coil-270 turns of #18(I think) on 6" PVC pipe with 1" space at the
> bottom and a lot of space at the top (8" maybe) has 4 coats of polyurethane
> varnish over the windings.

What is the actual winding length/height? A rough calc suggests about 
12" ?  So Ls = 4.5mH approx. Cs is about 7.8pF so by itself, the coil 
resonates around 850 kHz.

> Top Electrode-A makeshift toroid that isn't smooth by any means so I
> wouldn't count it's capacitance.
> Capacitors-6 saltwater types in a box giving about .0045 uF (I have another
> 6 if needed)

With Lp tapped to seven turns, your primary goes down to 610kHz 
approx.  I would most certainly count the capacitance of anything you 
stick on top. How smooth the surface is has no bearing on that 
question. 

     You can add around the same capacitance on top of your secondary 
as there is in the coil itself before its frequency becomes too low
for your primary when tapped at the full seven turns.

> Spark gap-two brass brackets with tapped holes carrying 1" wide x 1.5" long
> pieces of brass.
> Safety Gap- The same sort of thing as the spark gap except there is a groung
> plate in the middle.
> Transformer- One 12000V/30mA Neon sign transformer (I have 2 more if needed)

Assuming resonant charging and the gap opened up to fire around 17kV 
you only have around 650mJ in the primary cap. I don't think that is 
enough. I'd be surprised if your system generates more than 250kV. Can 
you draw sparks off the secondary with a ground rod? Have you 
measured the resonant frequency of the secondary with its topload?
What are the dimensions of the topload?

Malcolm

 > Chokes-none
> RF Ground-2' aluminium pipe
> Primary coil is resting on glass.  Secondary is capped at one end, sitting
> on the glass at the other. The wire to the primary coil is attached by
> alligator clips
> >From Scott
> 
> 
> 
> 
>