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Round vs flattened primary tubing


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From:  Robert W. Stephens [SMTP:rwstephens-at-headwaters-dot-com]
Sent:  Monday, June 08, 1998 12:54 AM
To:  Tesla List
Subject:  Re: Round vs flattened primary tubing

> 
> ----------
> From:  Steve Young [SMTP:youngs-at-konnections-dot-com]
> Sent:  Saturday, June 06, 1998 11:59 PM
> To:  Tesla List
> Subject:  Round vs flattened primary tubing
> 
> To all,
> 
> Winding a primary with refrigerator copper tubing in a pancake shape works
> well, as many posts attest.
> 
> Suppose the tubing was run through some rollers to flatten it out.  It
> would still have rounded edges for corona control, and it would have the
> same skin effect surface area.  It could now be wound more compactly which
> would increase the inductance per length slightly.  Or, the same spacing
> could be maintained, which would increase the turn to turn voltage
> breakdown.  Would there be any real practical advantage to such a primary,
> other than it could be secured easily by winding it through saw slots in
> the supports?
> I suspect the effort to flatten the tubing would not be worth whatever
> advantage there might be.  Comments?
> 
> --Steve

Steve,

I've often thought of trying exactly this myself.  You are absolutely 
correct about maintaining the conductive skin area (this 
configuration may actually be slightly better in this respect than a 
round conductor because the RF currents will tend to concentrate on 
the inner side) and how the round edges would be better for corona control 
than the sharp edge of copper ribbon, but I think the real advantage is how you
could gain more inductance for a given sized flat pancake while maintaining the 
same generous turn-turn spacing.  I prefer to make my flat primaries 
smaller in diameter than say the length of the secondary or the 
diameter of the topload.  This allows the coil base to roll through 
more doorways than would otherwise be possible, and helps reduce 
primary strikes by keeping this component _tucked-in_.  My 15-1/2 inch 
diameter secondary MTC-1 system rolls through a normal 31 inch wide 
man-door.

The big trick would be fabricating a quality, sturdy rolling machine 
for this operation.  You'd have to be extra careful that the plane of 
flatness didn't start to rotate on you.

Let us know if you attempt this.

Robert W. Stephens
Director
Lindsay Scientific Co.
RR1 Shelburne, ON Canada L0N-1S5
Tel: 1-519-925-1771   Fax: 
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