Re: big secondary coil

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

Actually, Robert, Greg built his a long time ago (in TCML terms).. I'm the
one looking for good ideas now.

I called my local pipe supplier, but large diameter( >16") plastic pipe is
pretty pricey (hundreds of dollars for 3 8 foot pieces) even for "non
pressure rated" SDR.  I haven't checked pricing on PVC ducting, which has
thinner walls and might be cheaper.  Also, that pipe gets pretty heavy, even
in thin wall.  A single or two plys of fiberglass is going to be striffer
and lighter than bulk PVC.

The sonotube is just a cheap circular form.

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Saturday, September 14, 2002 1:22 PM
Subject: Re: big secondary coil


> Original poster: "robert heidlebaugh by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <rheidlebaugh-at-desertgate-dot-com>
>
> Greg: I buy white PVC pipe from 1" thick down to 1/4" thick and from 5/8"
to
> 42" dia so playing with sono tube seams a waste of time, but if you must
> pull a tight layer of sheet polyethylene over it before you plastic coat
so
> the fiberglass wont stick. Phone your local irrigation supplier first.
>    Robert  H
>
> > From: "Tesla list" <tesla-at-pupman-dot-com>
> > Date: Fri, 13 Sep 2002 08:21:11 -0600
> > To: tesla-at-pupman-dot-com
> > Subject: Re: big secondary coil
> > Resent-From: tesla-at-pupman-dot-com
> > Resent-Date: Fri, 13 Sep 2002 08:35:33 -0600
> >
> > Original poster: "Greg Leyh by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> > <lod-at-pacbell-dot-net>
> >
> >
> >> Original poster: "Jim Lux" <jimlux-at-earthlink-dot-net>
> >>
> >> Casting about for ideas on inexpensive, but high performance, forms for
a
> >> secondary around 18" (50 cm) in diameter and 6 ft (2 m) long...
> >> [snip]
> >> But, what about taking the sonotube, putting 1 or 2 layers of
> >> fiberglass/resin composite over it (or, you don't even need glass, you
> >> could just use canvas as the fiber).. wait for it to cure (at least to
the
> >> "tacky" stage).
> >>
> >> Wind your coil.  Fix the windings with something (another layer of
glass?..
> >> urethane? glyptal?, etc)...
> >>
> >> Remove the sonotube by scoring and water soaking it.
> >>
> >> I think Greg Leyh did something like this for Electrum....
> >
> > Pretty much.  The sonotube was first wrapped with 3mil
> > poly however, to provide a mold release.  The sonotube
> > was mounted over a 22' steel arbor, as the paper tube
> > by itself was not rigid enough.  A winding jig supported
> > the steel arbor on both ends and rotated the tube for
> > placing the wire using a 2HP gearmotor.  After fully
> > wound, the coilform received a 1" thick fiberglass layup
> > using a chopper gun.
> > After the glass kicked, a router cut two fixed depth
> > grooves down the inside of the sonotube, and a pressure
> > washer removed most of the sonotube from the inside.
> > The mess in the parking lot was substantial.
> >
> >
> >> Questions:
> >>
> >> How much fiberglass on the inside?  The windings themselves will
provide a
> >> fair amount of strength. For more longitudinal strength, one could put
some
> >> sort of insulating beams on the inside (fiberglass tubing or PVC pipe)
> >>
> >> How would one make a mounting fixture for the secondary?  You could
"glass"
> >> in a piece of 3/4" plywood in the bottom.  Ideally, one would want to
be
> >> able to support the secondary horizontally as a cantilever attached
only at
> >> the base (sort of a worst case...)
> >
> > Electrum has 1" thick walls in order to support the
> > stresses of wind loading up to 150mph.  Lateral struts
> > inside the secondary were not possible as they would
> > obstruct the central manway.
> > Each end of the coilform has a thickened edge, and
> > the base end has four steel weldments laid up into
> > the fiberglass build.  The weldments support the
> > coil tower and anchor it to the concrete vault.
> >
> >
> > -GL
> >
> >
> >
>
>
>