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A new SRSG and Learning to Make Toroids

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

Hi all,
I am posting pictures of my recent projects, mostly consisting of a SRSG      
and learning how to make a toroid. 

The pictures are at


Pics 1-2 show a SSG made of threaded 
monel metal studs with silicon carbide inserts.
The thread is 3/8 - 16 and the brass nuts are the extra heavy
size that can be drilled and tapped for locking screws.


Pic 3 shows the 10 x 3/8 G-10 disc held in a chuck for  
edge truing on a wood lathe. After ruining several 
carbide tipped lathe tools, I found the best method of polishing the 
edge of the disc was to hold a large silicon carbide grinding
wheel up against the rim. The G-10 was cut on a bandsaw using
a hardened 4 TPI blade purchased from McMaster-Carr. I rig 
an elaborate dust collection system with the shop-vac whenever I
work any of the glass epoxies. It is highly instructive to see the 
large quantity of dust collected that would otherwise be inhaled
or spread all over the shop.


Pics 4-5 show the electrodes. Mounted in the disc are 4 threaded
studs of 3/8-16 monel metal. They are held in place with heavy brass nuts.
I used the monel metal studs because that's what I had. Brass studs may be 
The adjustable electrodes are 3/8 copper rod mounted in copper and Delrin.
Delrin plastic is very easy to machine and IMHO is far superior
to the other acrylics. But I'll never again try to drill copper bar. It's 
back to 
brass for me. I found the copper actually dangerous to drill. It's "sticky."
Perhaps someone can explain why the copper will grab even the smallest
drill and break it off. I must be doing something wrong. Even at low speeds 
the copper bar is a guaranteed drill buster. Brass is much easier to machine. 


Pic 6 shows the 1/2 HP motor and a rear view of the G-10 disc.
The motor armature has 4 flats milled by a local gunsmith. The synchronized
"lockup" is very clear under the florescent lights. The motor rotates in the
CCW direction so the torque tightens the nuts on the heavy disc. 


Pics 7-8-9 show a 4 x 18 inch toroid with 14 inch pizza pan hub caps. The 
insert is a 
4-inch rubber pipe sleeve and I used a fast hardening epoxy to hold the ends 
of the 
toroid together. The 1/4 x 20 brass stud can be seen at the center. It is the 
connection to the top turn of the coil. The pizza pans make excellent hub 
caps. Unfortunately, I cannot find larger diameter pans for larger diameter 
toroids. Tightening
the nut on the center stud compresses the whole toroid into a neat circle. 
The problem
is that the pizza pans can fall thru the center and it is difficult to get 
the pans centered on both sides at once. Spacers are needed. Just inside of 
each indentation along the rim of
the pan there is a small screw visible. Same is true on the other side. As 
the hub caps
are drawn together they will now seat against the inside spacers and I 
screwed the 
pans to the ends of the spacers. The spacers are 3/4 Delrin rod.

These toroids are made with the flexible aluminum ducting of the kind that is 
crimped together. The ducting is recognizable by the striations where the 
crimped seams are located. It is no good. This ducting is wound with 1.5 inch 
wide aluminum strips
that are crimped together to form a continuous duct. I found that as I tried 
to stretch and shape the ducting into a round toroid, I kept pulling the 
crimped seams apart. The results
is the aluminum foil bandage that covers an ugly, irregular seam caused by 
crimped seams ripping apart. Pie pan and pizza pan hub caps with the inside 
spacers work very well to produce a neat round toroid. Regrettably, the size 
of the pizza pan limits the diameter of the toroid, and the crimped ducting 
is an unacceptable mess. 


Pics 10-11 show the inside of a 6 x 28 toroid. This toroid is made with a 
"super-flex" ducting. Entering 5525K97 into the McMC search engine will show 
the available sizes of the "super-flex" ducting. This ducting is continuous. 
It is not seamed
together and it will not tear apart as it is stretched. It is heavy and it is 
pricey, but 2 1/2 ft
of the stuff can be stretched out to 30 feet. 

The seam is clearly visible in the pictures. I cut a 2 x 6 inch wooden block 
to use as an insert. The ends are screwed to the block with the pan head 
screws. This ducting produces a neat, flush seam. No need for aluminum foil.

I cut 3/8 plywood for hub caps. There is aluminum sheet on the outside (top 
and bottom)
of the plywood hubs. The eight inserts are 3/4 Delrin threaded for 1/4 x 20 
bolts. The toroid is heavy but it draws together into a tight, neat donut. 


Pic 12 shows the underside of the toroid mounted on top of the coil. The 
vinyl tape
holds the spacer to the top of the 24 x 4.5 secondary so the bottom of the 
toroid is 1.5
inches above the top of the secondary. The aluminum sheet and the 1/4 x 20 
can be seen.  


Pics 13-14 show two views of my 4.5 x 24 inch coil. This secondary is 1/2 of 
my 48-inch
bipolar. The secondary is 24 inches of # 28. Power input is 15kv -at- 150 mA for 
watts. The new toroid throws white hot sparks up to the overhead conduit only 
33 inches away, but it will also throw a 3-4 footer horizontally from a 
breakout point.  These longer  
sparks then turn upward for the remaining 33 inches to the overhead conduit.  
These are the kind of sparks that have already wiped out the ignition module 
from my furnace. They also blew the mind of the upstairs programmable 
thermostat. Not good.


Pic 15 is something completely different.


Happy day,
Ralph Zekelman