Re: Secondary Winding Done

In a message dated 96-02-12 16:14:17 EST, tesla-at-grendel.objinc-dot-com writes:

>Subject: Re: Secondary Winding Done
>Inspired by Chuck Curran's description of his secondary winding experience,
>thought I would recount my story, as I was engaged in the same activity this
>I had purchased the 6" acrylic form, 27" in length last November.  It wasn't
>until just after Christmas that I found the time to cut out the plywood end
>plugs to hold the steel support rod that was the basis of my manual
>winding rig.  I constructed the plugs so that they tapered inward slightly
>for a tight fit in the ends of the tube.  After drilling the center
>holes for the support rod, I tapped the plugs gently into place (or
>so I thought).  After constructing the jig to hold the spool of magnet wire,
>I set everything up at a comfortable height and prepared myself for an hour
>or so of winding.  To prepare the dusty surface, I wiped it down with a rag
>moistened with alcohol.  As I set the bottle on the floor, I heard what
>like a soft crackling noise.  Looking at the tube, I watched in morbid 
>fascination as a network of tiny cracks appeared at each end of the tube, 
>progressing the full length until they met.  At this point, the tube split
>fell crashing to the floor.  Arghhhh......
>Apparently my "light tapping" of the end plugs had produced micro-fractures
>which became macro-fractures after the cooling effects of the evaporating
>I ordered a few more lengths of tube and waited.  This time I fashioned the
>plugs to just fit into the open ends of the tube and did not taper them.  I
>used a few dabs of hot glue to hold them in place.  This worked fine.
>I found that the winding process worked best if the wire being fed from the
>supply spool was arranged such that the wire hit the form so that it crossed
>the windings that were already in place.  It was an easy matter to apply 
>tension with my thumb to keep the winding tight and firmly in place against
>the previous winding.  I was able to wind without even looking at the form
>after a
>few minutes of practice.
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>I finished up the form with two coats of clear, two-part epoxy resin.  As
>varnish on the wire was black, the coil looks as though it were painted
>with a thick, shiny black paint.  It's really quite attractive, in a
>hi-tech sort of way.  Even my wife and children admired it!
>I finished off with epoxying the plexiglass end gaps on, the one on the 
>grounded end with a tiny hole in the center for pressure equalization.
>I have yet to install the grounding plate.
>In my opinion, the acrylic form is the way to go.  Aside from my initial
>mistake, I found that the whole process (which I was dreading) was actually
>very enjoyable.  Just keep in mind that acrylic is not as strong or as
>flexible as PVC.
>Don Froula
>PS - Richard Quick's grounding plate instructions specify that the base wire
>from the coil should be soldered to the back of the terminal plate, after
>flattening out the wire with a hammer.  Can anyone think of a reason not to
>just solder the wire to the top front edge of the plate and epoxy into


Quite a story.  I bet the coil does look good.  I know I was sure proud of
mine when I finally got it done.  I used PVC with lots of coats of
polyurethane.  I would rather have used acrylic.  Your story of the acrylic
micro-cracking and completely falling apart reminds me of what we have
learned here at work.  I own a Yamaha golf car dealership.  We use acrylic
windshields on the new golf cars, both 3/16 and 1/4" thick.  I have tried
cleaning some adhesive residue off of these windshields before with alcohol
and got the same result that you did.  It did not fall apart but it did ruin
it with thousands of tiny cracks.  I am sure this is a chemical problem, as
opposed to temperature and pressure. 

We should alert anyone with a new (expensive) acrylic form not to clean it
with ANY solovents of any kind.  I would use only water or a mild soap

Ed Sonderman