Re: Stacked primaries

• To: tesla-at-pupman-dot-com
• Subject: Re: Stacked primaries
• From: "Malcolm Watts" <MALCOLM-at-directorate.wnp.ac.nz> (by way of Terry Fritz <twf-at-verinet-dot-com>)
• Date: Sun, 20 Dec 1998 22:58:23 -0700
• Approved: twf-at-verinet-dot-com

Hi Gary,

> Original Poster: Gary Lau  16-Dec-1998 2124 <lau-at-hdecad.ENET.dec-dot-com> 
> 
> Richard Craven has published an excellent paper entitled: "DESIGN
> IMPROVEMENTS IN TESLA COIL PERFORMANCE" on his web site, at
> http://www.users.globalnet.co.uk/~craven/ieetesla.html.  One suggestion
> made was in using two stacked primaries:
<snip> 
 
> I've never heard of this and can't visualize the electrical and mechanical
> configurations.  Is there any more info on this and has it actually been
> done?

I've built and used such primaries. The idea is not new. If you look 
at old spark radio installations you'll see this idea implemented as 
spirals sitting above one another. I've found that two identical 
coils stacked with spacing amounting to a couple of tube diameters 
gives a 70-odd% increase in inductance over a single layer coil using 
the same length of copper. It is also more compact.
     You can buy soft copper already formed as a two-layer spiral 
from pumbing merchants. The coil starts from the outside, winds 
inward, then climbs onto the second layer while spiralling outwards 
again, all turns in the same direction. A layer of plexiglass serves 
as interlayer insulation.

Malcolm

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