HERRICK'S RECIPE FOR A SPACE-WOUND SECONDARY

["Kennan C Herrick" <kcha1-at-juno-dot-com> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

1 "Sonotube" fiber concrete-form, 12" nom. dia., "litewall", x 52". 
Examine prior to purchase for smooth exterior.  My source:  White Cap
(distributor), San Leandro, CA.

2 pail covers, clear plastic, 12"; Cambro Co., Huntington Beach, CA
#RFSCWC12, or eq.  My source:  East Bay Restaurant Supply, Inc., Oakland,
CA.  Purpose: end-caps for the Sonotube.  Note: Cambro's white cover
(next item) will not fit White Cap's Sonotube; these do, very nicely.

2 covers, same type as above but white (less expensive).  Purpose:
stiffeners.

As req'd, clear RTV rubber; Dow Corning 732 recommended over GE brand. 
Source:  Local distributor.

As req'd, Jasco Water Sealant II.  Mfr:  Jasco Chemical Corp., Santa Ana,
CA.  Source:  Local distributor.  

~70', polypropylene cloth tape, 2" w/ adhesive 2 sides.  My source: 
McMaster-Carr Co., Los Angeles, CA, #77195A2 (36 yds).  Purpose: to
prevent shifting of the twine.

As req'd, twisted unpolished cotton twine, 10 ply, .054" nom. dia.  My
source:  McMaster-Carr Co., Los Angeles, CA, #1929T16 (2 1/2# cone; 1 is
plenty).  Alternate for greater spacing, #1929T28 (12 ply, .062"). 
Purpose: to provide a spiral track & cushioning for the wire and to space
the wire turns for increased Q and decreased effective resistance.

10#, 20 A.w.g., (~.033" dia.), "heavy build" (.0015"; 5400V) varnished
solid-copper wire.  Mfr:  Phelps-Dodge.  Distributor:  EIS Co., Los
Angeles, CA.  or my local distributor, Wirenetics, San Leandro, CA.  Be
sure to specify 1 piece with no splices.  10# is just enough.

As req'd, red insulating varnish, Krylon #1385 or eq. (aerosol spray
can). My source:  McMaster-Carr Co., Los Angeles, CA, #7437K16 (12 oz
can; 1 is plenty).  Purpose: to immobilize the wire.

Misc. hardware:  2 short insulated stranded-wire lengths, 2 solder lugs,
1 "banana" plug, 1 "alligator" clip, 4 6-32 nylon screws, 4 non-metallic
washers.  Source:  Local retailers.

4 securing straps; length a/r.  Suggested:  McMaster-Carr #94905K52 5/8"
hook/pile nylon tape (30'; plenty).  Purpose: to connect from coil top to
apparatus base-plate, to hold the coil upright.

2 drawer-pull handles.  McMaster-Carr #1646A11 or eq.  Purpose: to make
handling easier & avoid touching of the wire.

Purpose-built winding machine.  Source:  Up to you.

Absent a long-suffering and wholly cooperative spouse or friend, design
and build a winding machine, motor-driven and foot-switch controlled.  I
used a 1/70 hp gear-motor belt-driving the winding jig.  Said jig I made
starting with a sufficiently-long "2x4" to be C-clamped to the workbench.
 Bore 2, 1" dia holes near the ends of the 2x4 appropriately spaced for
the Sonotube + end-cap assembly (items 1 & 2), then slot the ends of the
2x4 longitudinally and install long wood-screws transversely so that the
holes may be made to tightly clamp 2, 1"-dia. wood dowels standing
upright.  Bore a 1/2" dia. hole transversely thru each dowel and insert
short pieces of 1/2" rod to support the Sonotube assembly horizontally
above the 2x4.

At one end of the 2x4 assembly, mount the motor assembly and also install
a V-pulley (or other), freely-turning on the 1/2" rod.  On the face of
the pulley, install a short pin, perhaps 2" from the center and merely a
1/4-20 bolt, to project out into a corresponding hole to be put in one of
the end-caps.  Drive the V-pulley via a belt from the motor assembly.

Inspect the periphery of the Sonotube for any dents; tap them out
appropriately from the inside. 

Using a pair of "aircraft" (compound-action) snips, cut away the
peripheries of the white pail-lids for a snug fit inside the Sonotube. 
Position them about 1/3 in from each end and secure them with a
continuous peripheral bead of RTV rubber.  Purpose: stiffening.

Prepare the end-cap pail-lids by cutting off their lifting tabs using the
aircraft snips.  Sand the cut areas smooth.  Drill a central 1/2" dia.
hole in each lid and an offset driving-hole in one. 

Trim each end of the Sonotube as req'd, assuring that each is
approximately orthogonal with the axis.  Apply a bead of RTV rubber fully
along each end, working it in, and then press on the lids.  Allow to
cure.

Apply one liberal coat of the Jasco sealant to the outside of the
Sonotube.  Allow to dry.

Install 16 strips of the poly tape, spaced -at- 22 1/2 deg., axially onto
the Sonotube.  Extend each strip fully to each end-cap, cutting it off
with a sharp knife.  Press down firmly all along.

Prepare a jig or jigs for holding the twine and the wire.  Provide
hold-back means so that appropriate tension may be maintained while
winding.  For ease in acomplishing the winding, position the jig(s) 12'
or more away from the mid-point of the Sonotube/winder assembly.  Clamp
the jig(s) to a firm surface.

At an appropriate angular location at the end from which winding is to
begin, drill a 1/8" dia hole on a shallow angle, starting at the juncture
of the end-cap flange and the Sonotube, in the winding direction, and
ending at the approximate mid-line of the cap's internal shoulder.

Feed the twine-end through that hole and temporarily tape it; it helps to
feed the twine into a thin-wall metal tube first, then pass the tube &
twine thru the hole.  Then create a spiral track on the surface of the
Sonotube, for the subsequently-wound wire, by winding on 1 full layer of
twine.  To facilitate this, a) remove the poly-tape's  release-strips
only several inches at a time and b) carefully close-wind the twine, onto
the tape, keeping a moderately firm tension, so that gaps are minimized. 
Fully fill the space between the end-caps with the twine.  Use a glove to
spare the epidermis.  Coat the twine with Jasco sealant and allow to dry.

At the "far" end, drill a hole similarly to the starting-hole.  On both
internal end-cap shoulders, mount a solder lug and in addition, a wire
strain-relieving clip on the "top" one.  In the "bottom" end-cap, drill a
1/8" dia. hole radially thru at the approximate mid-line of the end-cap's
flange for the return-wire's exit.  Moderately countersink the outside of
the hole for strain-relief.  Drill & tap 4, 6-32 holes radially -at- 90
degrees on the approximate mid-line of the "top" end-cap's outer
flange-surface, oriented them as desired with respect to the
ground-wire's exit hole.  These will be for attaching the hold-down
straps.

Thread the starting wire-end through the hole provided, scrape off the
varnish, pull snug, wrap around under the solder-lug's screw-head, and
tighten the screw.  Then wind on the wire, carefully keeping it in the
track provided by the twine.  Maintain a moderately firm tension.  Again,
either use a glove or else a short piece of tube or rod with a ~.04" dia.
hole for guiding the wire.  The twine will compress somewhat, providing a
residual tension that will prevent any subsequent bowing or loosening of
the wire prior to final varnishing.  Keep a piece of tape handy for
securing the wire during rest-breaks.  There will be a number of those,
as when winding the twine--the task is terminally tedious.

At the "far" end, feed the wire-end through the hole provided & proceed
as before to attach it.  If you are compulsive you may now inspect the
winding and tweak here & there, with your fingernail, to improve the
spacing.  I don't see it as necessary:  Somewhere, the varnished turns
are going to nearly-touch; you can't find all such places.  Depend upon
the varnish to keep the turns apart, copper:copper (good for 5400V/turn,
presumably).

Remove the assembly from the winding jig, mask off the ends as desired,
stand upright, and apply the Krylon varnish as desired.  One 12-oz. can's
worth should be plenty.  Allow to dry.

Attach a handle where appropriate on each end-cap.  That the handles are
metal should cause no problem:  The top one will reside within the
toroid's i.d. and the bottom one, if used, should be in a low field
gradient with respect to ground (with some attention paid to it while
designing your primary apparatus).

Connect the end wires--a short piece with alligator clip to connect to
the top electrode and a longer piece as req'd, with banana plug and at
the "bottom", to connect to the primary apparatus.  The bottom wire is to
be fed through the radial hole provided in the end-cap.  

Attach appropriate lengths of hold-down strap to the top end-cap using
nylon screws and non-metallic washers.  In the primary apparatus, provide
appropriate eyes for accepting the strap ends.

There you have it!  Connect the banana plug to ground or whatever, plop
your electrode on top, clip onto it with the alligator clip, and Fr will
be approximately 100 KHz (using the .054" twine).

Ken Herrick
________________________________________________________________
YOU'RE PAYING TOO MUCH FOR THE INTERNET!
Juno now offers FREE Internet Access!
Try it today - there's no risk!  For your FREE software, visit:
http://dl.www.juno-dot-com/get/tagj.