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Re: [TCML] A new guy with a primary threaded through holes
:L or K style "soft" copper tubing work hardens every time it is bent
slightly, or "skotched" as you call it.
I use 3/4" wide x 1" high x 7-10" long delrin blocks, then machine a series
of "U-shapes" into the blocks using a ball nose cutter on a milling
machines. It's fast, easy, and the copper tubing quickly snaps into place.
No excessive bending and work hardening of the copper.
Dr. Resonance
On Mon, May 17, 2010 at 6:55 PM, Joe Mastroianni <joe@xxxxxxxxxxxxxx> wrote:
>
> My primary coil - http://gallery.me.com/iceowl
>
> It is with no small degree of chagrin that I note Greg Leyh will not be
> appearing at this week's Cal. Maker Faire. Were it not for his
> demonstrations last year I would not be reading this list now, and typing
> with raw fingers after threading 42' of 1/4" copper tubing through 96
> stanchion holes. I am in process of creating my first coil thanks to Greg
> and his small 20' purple arcs that spanned a big chunk of the show floor.
>
> Alas, even the wife was so taken by Greg's display that she consented to my
> coiling. Even encouraged me. Is even helping. Four hands winding the
> copped through the holes worked better than two. This is how it starts, I
> guess.
>
> Ebay luck shone down upon me a few months ago and I scored 15/30 NPT. I
> promptly built a jacob's ladder, and just as promptly grew bored with it.
> Consequently I have been amassing parts to build my first coil. The
> garage is beginning to fill with those white/red/blue Priority Mail boxes.
> I can barely get the car in. After a trip to TAP plastics and an evening
> throwing numbers into JAVATC I decided to start building. Now there is no
> room for the car at all.
>
> Previously, I had bought an 18 page paper written by a guy who went through
> the mechanical structure of a static spark gap coil, and he advocated using
> plastic cutting board material for the stanchions, and using 4. Four
> seemed to offer less structural integrity than 6, and 6 (or 8) looked
> better. I decided that it would be very difficult to thread the copper
> around 8 stanchions placed 45 degrees apart because of friction and also,
> the 1/2" polycarbonate would force the copper to follow a straight line
> through its 1/2" length, which I felt might necessitate lots of bending. So
> 6. I decided on 6.
>
> I built 6 stanchions to hold the primary by cutting "L" shaped pieces from
> 1/2" polycarbonate/Lexan I got from the Tap plastics cast off bin. With my
> drill press I built a jig out of wood which allowed me to precisely drill 15
> holes in the long leg of the "L". I drilled 5/16" holes and stepped them
> inward by a couple 32nds on each subsequent stanchion to account for the
> spiral winding. There is no engineering involved in my decision to drill
> 5/16" holes other than I knew I wanted a hole bigger than the O.D. of the
> 1/4" tubing and the only bit for drilling plastic they had at Tap plastics
> that was bigger than 1/4" and smaller than 1/2" was 5/16". Turned out to
> be fortuitous.
>
> That evening I subscribed to pupman.com - which I had not previously
> subscribed to because, well, no pictures. What a massive mistake. I
> learned at about 2AM on Saturday morning that it would be impossible to
> thread the copper through the 1/2" polycarbonate. Several had tried and
> failed, as evident from their exasperated postings on this auspicious site.
>
> But I had already made my investment in time and $$. So my choices were to
> toss out what I had done and go the
> LDPE-with-"C"-shaped-notches-instead-of-holes route, or beaver on mindlessly
> as if I had never read the posts.
>
> The next morning acrylic cement I glued the stanchions to a lexan circle I
> also got at Tap. When you use that acrylic cement it bonds pretty
> completely. It's as if the plastic becomes one piece. This was also
> fortuitous.
>
> At 2AM on Sunday morning I discovered some posts on pupman that described
> some intrepid soul, some years ago, who actually accomplished what I was
> about to try. Somewhat cryptically he said, "it's possible and I just did
> it and it wasn't so hard". Though he did not describe his technique much
> other than to mention the term "scootching".
>
> I have learned what "scootching" is. But just to be safe, and to allow for
> extra play, I beveled (countersunk?) each of the holes about 1/8" with a
> fine stone bit on a dremel. I figured this would make it easier to thread
> the copper as it came in to each hole at an angle.
>
> When daylight broke I began threading the copper. Even though my stanchions
> have more holes, I had decided to thread 13 clockwise turns. The 50'
> section of copper I got came in a coil. I laid this coil over the
> stanchions in the winding sense I desired and began threading the tubing
> using the natural curve of the copper to follow the curve of the hole
> pattern on my stanchions. The first 2 turns went swimmingly, and I wondered
> what all the fuss was about. I put two hands on the tubing, forcing it
> through the holes gently, turning it as if it was some sort of valve. I
> could push the copper through the holes about 1/2" with each grunt. The
> next 4 turns were a bit harder. And in fact, by the time the 4th turn was
> through, I could only move the copper about 1/8" or maybe only a couple
> millimeters with each effort of the hand. This took me about 90 minutes.
>
> With a cup of coffee in hand I took a rest break, read more pupman, and
> discovered someone suggested using Windex as a lubricant.
>
> I will say it would have been completely impossible to thread the copper
> through the holes without some form of lubricant. By the 5th turn the
> friction was so great the coil could not be passed through the stanchions at
> all. Slathering on windex - I suddenly had the ability to "scootch" the
> coil clockwise about 1/16" with each twist. It didn't get much better than
> this. In fact, it got worse. As I reached the inner turns of the coil, I
> was squirting Windex into each hole pretty much with each turn of the coil.
> By the time I got through the 10th turn, the coil was only rotating 1 or 2
> millimeters with each "scootch". I had to manually twist each turn of the
> coil individually, sometimes starting from the inside, sometimes from the
> outside.
>
> I believe I have put six hours into the coiling of the copper. It was not
> easy. The results seem to be aesthetically pleasing, and of course, it's
> very structurally rigid, especially since the windex has all evaporated now.
>
> With regards,
>
> Joe
>
>
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