1) Use 1/4 turn sections of the copper tubing and link each 1/4 turn 
section together with massive copper blocks, 5 x 5 inches square x 6 
inches long.  Butt the primary 1/4 turn sections together and use a 
lot of brass setscrews to firmly capture the 1/4 turn sections in 
the brass blocks.  I'm worried the resistance might become an issue 
with nearly 12 "copper connectors" joining the pieces together.  I 
would like to use he large 4 inch copper tubing but it seems joining 
them together might be a problem, and trying to haul it assembled 
just will not work as the height would be too much for interstate 
bridges and city streets with cross-wires, etc.
2) It's not possible to use 2-3 inch dia. copper cable as the weight 
would be too high for assembly handling.
3) Perhaps use 1 inch dia copper cable and then wind 4 of these 1 
inch dia. lengths in parallel to form the 3.5 turn 
primary.  Handling 1 inch dia. copper cable should not be too much 
of a problem for a crew working with a small crane (which we will 
have onsite to erect the sec coil and attach the large toroids). 
With this idea, I probably would join the 4 cables together every 
1/4 turn with some solid machined copper clamps to insure even 
current distribution in the primary.
I know there are some great thinkers on this list and a few good 
machinists, so ideas please!!   We are open to consider every idea 
and try to adopt the one we think will work best.
Best regards,
Dr. Resonance
Resonance Research Corp.