Re: Space winding question

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

Original poster: "Barton B. Anderson by way of Terry Fritz <twftesla-at-uswest-dot-net>" <tesla123-at-pacbell-dot-net>

Hi John C, Malcolm,

Sorry to take so long to reply.

Tesla list wrote:

> Original poster: "Malcolm Watts by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <m.j.watts-at-massey.ac.nz>
>
> On 15 Mar 01, at 7:53, Tesla list wrote:
>
> > Original poster: "John H. Couture by way of Terry Fritz
> > <twftesla-at-uswest-dot-net>" <couturejh-at-worldnet.att-dot-net>
> >
> > Malcolm -
> >
> > The TPI must be coordinated
> > with the gauge and the insulation thickness to give an overall
> > thickness of
> >
> >       TPI = Turns / Overall thickness

Yes, I agree. Three factors affect TPI.
Insulation thickness, bare wire diameter, and any spacing between adjacent
insulation. This is exactly
what JavaTC performs  TPI = 1/(bare wire diam. + spacing + insulation). All
the variables are taken into
account. The problem is that one of these variables was assumed. You told
us you used 2 mils instead of 1
mil in the program. Why? The wire table says 1 mil (or near - actually
0.0009 inch for my American Wire
Table). Why did you enter zero for the spacing? Are we assuming that a
closewound coil has zero spacing?
This isn't true for most real world coils. We all wind differently and to
different degrees of accuracy.
That's exactly the reason JavaTC has a spacing factor. This is where the
extra mil should have been
inserted.

I've found that "actual" TPI is a little lower than calculated. I once
measured TPI at different points
along the coils length. After counting each turn "one-by-one", I ended up
with less turns than calc'd.
Why, because there is inherent spacing between turns even on a nicely wound
(attention to detail, etc..)
coil. This inherent spacing builds with turns. There is "no way" for a
program to calc this factor. It
must be measured and entered after the coil is wound. If a coiler is trying
to wind with zero spacing,
then zero should be used initially.

I wish I had Nates coil in front of me. I'd count the turns (yep, I'm that
boring - but ambitious!). I'd
bet a lunch TPI is actually lower. When TPI is lower, the spacing factor
must be higher. Inductance
decreases, Fr goes up. The primary inductance must then decrease and tune
at fewer turns.

JavaTC was designed to enter a coils design dimensions like the rest, but
this is only the "first step".
Once the coil is built, the coiler can measure TPI at various points along
the coil and average them or
count turns (not a lot of fun, but accurate). This info is then fed back
into the design for finer
detailing especially in the tuning portion. Unfortunately for Nate, 30awg
is very small and difficult to
count. The way this is done is by inputing the basics: height, diameter,
bare wire diameter, insulation
thickness, and then changing the "spacing" input until TPI calc'd equals
the coilers measured value.
There is no other way to accomodate this "real life" factor in any program.
But is real, and the program
accomodates it.

It also works well for space wound coils obviously. Good program for those
arm chair cowboy days
wondering what some of the differences are between 1/2" spacing or 1/4", etc..

> > I believe that this is a problem with Bart's great program as I
> > mentioned in another post. I haven't checked this out completely but
> > was waiting for Bart's comments. The rest of his program gives the
> > same answers as mine but Bart's has more information.
> >
> > The coil length is always equal to the TPI times the number of turns.
>
> I think not. Not in a spacewound design.

Malcolm, John is right. TPI is the number of turns per inch (spacing included).

Take care,
Bart A.