Next job is to form the 1/4" copper tubing into the approximate spiral required. I say approximate as it will be the drilled holes in the 8 support combs that will accurately position the primary coil. The tubing I purchased came in a spiral pack as, I presume, most 50 foot (15 metre) packs will come. The biggest tip is to leave it spiralled. Don't try to straighten it. I found that it needed very little work to open up the spiral to the approximate shape required. I used a Mac program called EasyDraw which has a spiral tool so I punched in a few settings and dragged the spiral out to the approximate diameter and the approximate number of turns. The resulting spiral was exported as a pdf and then printed across 6 pages of A4. I carefully taped the sheets together so I had a full scale plan of the spiral.
I had to be careful when placing the sheets together, the HP printer I used will not print right up to the edge of the paper so I had to work out if the sheets needed to be overlapped or placed edge to edge. After measuring I could confirm that the pages did not need to be overlapped.
Above is the end result on the dining table. The coils should be spaced between 1/4" and 3/8", I opted for 7mm which is just over 1/4".
This is the tubing straight from the packet. Remember, don't be tempted to straighten it out.
After about 15 minutes of easing the coils open using the plan as a guide. It will need a little more work before I move on to the next step which is drilling the support combs.
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That is the perfect shape for tubing the coil. If we do it manually I think it's a little bit hard.
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