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RE: Half wave/ bipolar coil

Original poster: "Ralph Zekelman" <gridleak@xxxxxxxxxxxxxx>

Before you start winding the copper tubing, place 1/2 of the plastic
spacers
onto the form so the tubing slips into the pre-drilled half-hole. The
method for
making these spacers has been described several times on the  Tesla
list.
When the solenoid is fully wound put the other half of the spacer over
the
finished turns and fasten with nylon screws. Cutting the Walmart cutting

boards into coil spacers is OK, but white Delrin  has much better
machining
properties.

A large coil of roofing flashing makes an excellent coil form for larger
solenoids.
The springiness makes for a rigid form that can be set for the correct
diameter.

Ralph Zekelman


-----Original Message-----
From: Tesla list [mailto:tesla@xxxxxxxxxx]
Sent: Wednesday, March 23, 2005 10:38 AM
To: tesla@xxxxxxxxxx
Subject: Re: Half wave/ bipolar coil

Original poster: jdwarshui@xxxxxxxxx

Hi: Lee

Jared again, with advice on a primary for your half wave:

  The only gain you would get by splitting your half wave secondary in
two is that you would be able to independently adjust the coupling.

  Our first half wave was designed this way and it was a mistake. When
you split your secondary into two parts you are begging for flashover
near the current nodes, as the exposed edge of the solenoids now
represents a sharp edge with a minuscule radius.

Solenoid primaries are easy to make by winding fresh copper tube about
round objects. You can change the coupling by stretching this spring
out  a bit. It will change the inductance as you stretch it so you
would need to re tap afterwards.

I would recommend a 20inch form for your primary and keep the winds
about 1/8 inch to 3/16 inch apart. The more primary winds you can
squeeze in the better off you will be.

  It is easy to tune a primary with a lot of turns. If you have 20
turns and you are off by one turn you will hardly notice. But with six
turns you will be struggling to find the sweet spot.

  The leads to the primary become a big hunk of the inductance when you
only have six turns, very difficult to tune around this.

We have built a few coils with 18  to 20 turn primaries, and have very
much liked the results.  I suspect that larger primaries cut down on
current density and thus reduce resistive loss.


Good luck from Jared