The Geek Group Primary Winding Method of SCIENCE (da da da daaaa)

["Christopher Boden" <chrisboden-at-hotmail-dot-com> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

With all the posts I've seen about blisters, ulcers, and grief winding 
primaries I can't figure it all out. It took us (Neemie and myself) less 
than 10 minutes to wind and tweak a beautiful primary for the SAM project. 
It's a 15 turn 60' (apprx, it's 50' with a splice and a little extra) 1/4" 
Copper tubing primary. So to possibly help someone out there, or find out 
what I did so terribly wrong I'm posting the whole process we used here. 
Critique anyone?

Alright, this assumes you have the following.

A 6" secondary coil (6X24" windings)
A vertical mill with a 1/4" flat end mill (though a ball end mill would work 
great!)
a 24"X1/2" UHMW Primary table
8 pieces of 3"X12"X1/2" UHMW
18 or so 1/4"-20 Nylon screws

UHMW= Ultra High Molecular Weight Polyethylyne (sp? yeah, I know)
UHMW is Gods gift to Tesla Coiling. It's wickedly strong (I can stand on my 
primary table), machines like butter, and an amazing insulator that doesn't 
absorb water. I love it :)

Chuck your 1/4" bit in a nice morse taper collet and set your Vertical mill 
for a low speed setting. Too fast and you'll burn the UHMW, too slow and it 
galls like brass. The chips should be nice and consistant, rather large.

Stack your plates so that when you cut them from the first to the last 
(number them) you make a staggered pattern though the series that allows the 
primary to transition smoothly from one turn to the next. This is a LOT 
easier than it sounds. From plate 1 to 8 you should move about .75 inches. 
(.25 for groove 1 - .25" for gap - .25" for turn 2)

Mill as many slots as you can fit on the plates. You want 1" from the 
primary (we used .75 I think, it works) keep in mind this is the RADIUS so 
at .75 to turn 1 that's actually 1.5" clearance). Mill to the outer end with 
.25" slots that are .75" deep with a .25 gap between sides.

Make your cuts slow and smooth. .30 passes are fine, this is like machineing 
butter.

Clean and deburr the plates

Unclamp and layout the plates inverted all aligned (flat) the grooves should 
form a perfect pattern.

Measure 2 evenly spaced holes on the bottom of each plate. Drill about .5" 
deep and tap for 1/4"-20

Drill your primary table to match the holes (do not tap)

Mount the plates in order. Be carefull torqueing doen the bolts, nylon 
breaks easy, have a few extra. The heads snap off with little effort. They 
can be removed easily though.

Now, 50' coils of copper tubing come COILED! USE THIS TO YOUR ADVANTAGE!
Start at the center and SLOWLY work outward. This takes 4 hands and 
patience. Copper will work harden, if you keep bending it it stiffens 
quickly , becomes brittle, and will actually tear and break right off! 
(though you have to WANT to do it, it can happen)

The tubing is .25ID! the slots are .25"ID too. The tubing will JUST fit 
snugly into the slots. You may even notice the tabs bend a bit, this is 
alright, they won't break.

Keep going untill you run out of tubing, you should get about 11 turns. 
Splice for more if you need them (you probably won't) we thought we did, but 
since learning the intricasies of tuning have seldom needed all 11 that we 
had to start with! 9 is about right.

This has made a rock solid, reliable primary that has been HEAVILY abused 
for 6 months of active coiling. This isn't a Garge Queen coil. It's set up 
and tore down on a regular basis for demos. It's beat on and bent daily and 
always comes right back with a little tweaking and love.

I got no blisters, no swearing, and no problems winding it, and have NEVER 
had a primary flashover problem.

I honestly believe this is the best possible primary design for this 
application. For the bigger coils, I like copper ribbon in a similar 
mounting method.

Christopher A. Boden Geek#1
President / C.E.O. / Alpha Geek
The Geek Group
www.thegeekgroup-dot-org
Because the Geek shall inherit the Earth!

_________________________________________________________________________
Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail-dot-com.

Share information about yourself, create your own public profile at 
http://profiles.msn-dot-com.