Bipolar disorder - part 2

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Parpp807-at-aol-dot-com>

Terry has posted 11 pictures of my bipolar coil(s) at:

        http://hot-streamer-dot-com/temp/RalphsCoil/

The reengineered mounting for the secondary is shown 
in BP 6 jpg. This is a big improvement over the unstable 
pedestal mounting for only a small compromise in the 
insulating properties. The Delrin sheet is 1/2 inch thick. 
The long axis of the coil is 12 inches above the base, and 
the support is 12 inches wide. I wrapped some
silicon rubber around the coil where it rests on the 1 inch 
wide cradle. Velcro holds the coil
tightly in place. The primary is supported on a piece 
of 3/4 Delrin rod. Yes, the side supports are fastened 
to the piece of 2 x 4 with 1/4 - 20 Nylon bolts tapped into the 
wood. It works. I didn't want to use any metal angle brackets. 
McMaster-Carr is a good source for plastics and plastic hardware.

The new toroid(s) is shown in BP 7 jpg
The toroid is 4 x 15. This is the first time I made a toroid and 
I went to school on these things. The big error was in using 
a spiral wound ducting. This is a solid tube
but the pleats are formed in a spiral. Nice stuff, a 2.5 ft length 
will expand to 30 ft. Not a misprint. But the spiral winding 
makes it difficult to get a straight edge for the seam. 
The first toroid is not too good, the one in the picture worked 
out fine. To join the two 
ends I used a rubber pipe sleeve 
just slightly smaller than the ID of the ducting. An 
epoxy cement holds the 
ducting to the rubber insert. The epoxy should be allowed 
to setup a little before slipping
on the ducting. A few minutes of holding and the bond was set. 
Then I did the second end in the same way. The results is 
a neat seam that can be seen in BP 8 jpg. Mounting the toroid
to the coil is when I got the toroid into a round shape. 
I used two aluminum
pie plates for hub caps. There is a piece of acrylic sheet 
between the pie plate and
the coil end and on the other side of the toroid. This 
distributes the pressure as the entire assembly is 
tightened into roundness.

The toroids lowered Fr down to 146 kHz from the 
original 256 kHz. Csec is now 10.7 pf. 
Ls remains the same.
I had to retune the primary just slightly.

The next step in reducing the corona losses was to 
make two rods for the rabbit ear antenna. 
This is shown in BP 8 jpg and BP 9 jpg. 
I got a 10 ft length of 1.25 inch OD aluminum tubing. 
An electrical contractor
put a nice smooth bend of large radius and no kinks 
onto each end of the tube. 
I then cut the 10 ft tubing into two sections. The bend 
begins almost a foot from the end of the coil. 
The entire length of each rod is covered by
thick-walled vinyl tubing. No corona along the rods. 
The rods have to swivel  
to change the gap distance. I made brass swivel 
joints out of 1-inch diam
brass rod.  One section screws onto the end of the 
mounting stud. The other half
is a close fit into the end of the aluminum tubing where 
it is held by several 6-32 screws.
The E-field is now much better behaved and there 
is no corona off the end of the coil
or from anywhere along the antenna rod. But the beast 
is getting heavy and the rods now have to be resting on 
crutches. They can swing parallel to the table top but in no way
can they be raised vertically without bending the 1/4 - 20 
mounting stud at the end of the coil.

BP 10 jpg shows the coil ready for firing. The SG is visible 
to the left on the voltswagon.
BP 11 jpg shows the final moments of the completed coil. 
The long axis of the secondary is 13. 5 inches above the 
table top. We are now around 2.5 ft below the light fixture 
and the bottom of the toroids is only six inches above the 
table top. I have to raise the ceiling. 

I got a nice white hot spark around 43-44 inches long. 
With the gap that large, the
sparks are pouring off from the bottom of the toroids to 
the plywood table top. Visible in
BP 11 jpg are sheets of Delrin, G-10, and acrylic trying to 
insulate from the sparking toroids. It doesn't work.

I never got the full 48 inches of spark and the question of 
getting a spark longer than the physical size of the coil 
remains unanswered. My fundamental error was one of scaling.
I should have made the secondary 24 inches long and 
proceeding from there to properly shape the E-field, I think 
I could demonstrate a spark longer than the length of the secondary.

The 48 inch coil has been cut in half to resurrect itself into 
a bipolar twin coil.
Without trying too hard, the twin is already producing a 60 inch spark. 

Coiling is a great hobby.
Altho my basic experiment failed, it was a success. 
Considerable learning has taken place,
and learning just for its own sake needs no further justification.

Cheers,
Ralph Zekelman