[TCML] A new guy with a primary threaded through holes

[Joe Mastroianni <joe@xxxxxxxxxxxxxx>]

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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