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Re: Secondary Specs

Subject:  Re: Secondary Specs
   Date:  Thu, 17 Apr 1997 21:14:36 +1000
   From:  Phil Chalk <philoc-at-ozemail-dot-com.au>
Organization:  Secure_Logic
         To:   Tesla List <tesla-at-pupman-dot-com>
 References: 
            1

> 
> Chip,

Many thanx for your thoughts;

 
> Hold on there!  a 10" coil would be way cool, but I'd highly recommend
> something smaller such as a 3" or 4" diameter coil.
 

You're right, of course, Mike Hammer & myself had already convinced me
it 
was a dumb idea !  I get a bit carried away sometimes.  I also like to
'do 
it once & do it properly', but I know I need to ramp up my experience on 
this first.

 
> Granted I didn't have access to as much knowledge when I started, as you
> do through the list.


It has been invaluable !

 
> Another consideration is where you go from 10".  


Right again !

 
> For a 3" coil, I'd go with 1/4", a 4" coil, 3/8", a 10" perhaps 1/2" or
> 3/4" (I don't know about the larger sizes as I have no experience and
> don't remember the recommendations made by others)
Yep, it's 1/4' copper, now.
 


> You can save yourself a bunch of money if you do the following things:

> 1) Improvise -- keep your eyes open for things such as pipe scraps,
> 2) Build it if you can, rather than buy it.  I'm a fan of the TCBOR
> 3) Shop the ham fests.  Keep your eyes open in particular for variacs,
> wire, and anything else you may find useful.
 

1) & 2) I'm pretty big on already. As for 3), 'Hamfests' are few & far
between here, unfortunately.  There's a beauty, once a year, about 60
miles up the road - I've been once, years ago, but next time ......
I know what you mean though, and there are some 'junky' shops around the 
place with some cheap goodies.


> >  A 3" coil can give you streamers up to 16" long as I recall.


Good, that'll do me for a first attempt.

> > P.S.  Anyone know of a source of 'nice' aluminium (copper ?, whatever)
> > torroids ?
> 
> You can build them yourself, and they look half decent.  I use flexible
> aluminum ducting and some sort of disk in the center.  

Yes, Ive seen these, but I'd really like a _nice_ spun, or machined, or 
whatever, smooth, polished one, as I've seen on some coils in pix on the
net.  I realise it won't be cheap, but they really enhance the
appearance
of the coil when it's off, I think.


> 0) I'm assuming that you know the size of the toroid you wish to make.


No, I don't know - the coil will now be 2.75" diameter, by 20-25" long
-see
below.  Can you suggest a size(range) ?  Also, given that you know the
self-
capacitance of a sphere or torroid, how do you calculate how it will
affect
the resonant frequency of the secondary ??  Do you simply treat it as a
series
LC circuit ?

The 'new' coil now, first up, will be wound on 69mm (2.75") OD 3mm wall
clear acrylic.  I have 500g, about 230m (250yds), of .56mm (it measures 
0.63mm with the insulation)(0.022") very close to 23 AWG enamelled
copper 
wire.  Currently I plan to wind about 1000 turns, nearly 25" winding
length.

Current wisdom seems to suggest that 800 turns (19.8"), or probably
better,
900 turns at 22.3".   Any comments, anyone.

So once again, thanks.  Sorry for all the questions but it's just such a
tempting resource.

Cheers,
Phil Chalk.