RE: Designing BIG Secondary Coil

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

Original poster: "Dave Hartwick by way of Terry Fritz <twftesla-at-qwest-dot-net>" <ddhartwick-at-earthlink-dot-net>

Malcom,
What is the composition of that sewer pipe? You're not talking about terra
cotta pipe, I assume?

How are you accomplishing space winding?
Dave H



Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<m.j.watts-at-massey.ac.nz>

Hi Dave,

On 5 Sep 2002, at 19:28, Tesla list wrote:

> Original poster: "Dave Hartwick by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <ddhartwick-at-earthlink-dot-net>
>
> Malcom,
> Fascinating recommendations. With a confined Lab, I've been thinking small
> dia secondaries, but this really makes no sense. The vertical height is
the
> problem. Why not go with large diameters?
> Of course, there is a minimum vertical height limitation, lest excessive
> striking of the strike rail become a problem.
>
> A suitable form for such large dia secs is always a problem. I think the
PVC
> tubing I've seen at the 12" mark has distressingly large wall thickness,
but
> is this a real world issue? Lexan or Plexi is out of the question for $$
> reasons. Sonotube is known to inflict low Q, though it has been used on
very
> large coils.

Re the wall thickness: the best secondary I have wound to date
followed the guidelines for a spacewound coil and was wound on -
gasp!- a 10" diameter piece of thickwall sewer pipe. It outperforms a
closewound coil wound on a skeletal former wrapped with 1/8" thick
HDPE sheet with a 17" diameter and closewound with wire that *didn't*
meet the closewound guideline.
    I met with complete failure winding a 12" coil onto sonotube, and
that was with the tarred layer removed and the remains for the form
varnished *and not pre-dried* :(  The measure unloaded Q of that
coil, spacewound and all was a miserable 30 - 40. That coil went out
in an annual solid waste collection.
    The unloaded Q of the 10" sewer pipe coil (not pre-varnished BTW)
was about 300.

Regards,
Malcolm

> I've thought of building a collapsible form, finishing the windings with
> epoxy, collapsing and removing the form, then inserting a modest High-Q
> structure internally for structural support.
>
> There are various tanks, trash buckets, made of HDPE, etc, that could be
> used.
>
>
> Dave Hartwick