Round vs flattened primary tubing

From:  Steve Young [SMTP:youngs-at-konnections-dot-com]
Sent:  Tuesday, June 09, 1998 12:21 AM
To:  Tesla List
Subject:  Re: Round vs flattened primary tubing

> 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
> > 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
> > same skin effect surface area.  It could now be wound more compactly
> > would increase the inductance per length slightly.  Or, the same
> > could be maintained, which would increase the turn to turn voltage
> > breakdown.  Would there be any real practical advantage to such a
> > other than it could be secured easily by winding it through saw slots
> > 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
> 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.

Robert:  RE the increased inductance for a given sized primary.  Since my
post, I played around with the Wintesla2 program to see the effect of more
compact primary windings.  Interestingly, the inductance was about the
minimum for wire diameter equal to the turn to turn spacing for 1/4 inch
wire or tubing.  The inductance goes up a little as turn to turn spacing is
either decreased (mutual coupling effect?) or increased (wire length gets
longer).  However, the change in inductance only amounted to that which
would be gained by increasing the total number of turns by a tenth of a
turn!  (I have no idea if Wintesla2 is producing completely correct
results.)  Except for fitting through a doorway, the other benefits don't
seem worth the effort.


> 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: 
> *Custom built Tesla coils, etc., for museum display 
>  and special effects work.
> *Canada's largest publicly accessible wall-to-wall
>  indoor lightning show...by appointment.
> *Future home of Electric Science World, 
>  educational/entertaining Theatre of Electricity.
> *Antique TV Museum...in search and acquire mode now.
> ~~~~~~~~~~~~~ Inquiries welcomed! ~~~~~~~~~~~~~~~