Re: Reducing toroid size

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

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <FutureT-at-aol-dot-com>

In a message dated 6/9/02 7:20:14 PM Eastern Daylight Time, tesla-at-pupman-dot-com
writes:

Yes, you'll have to move the tap position with the smaller toroid
to keep it in tune.  I mentioned that in my prior email.  Is there
some reason you don't want to do that?  Usually the toroid size
is not used to tune the coil.  Rather the primary tap position is
used to tune to coil, dependant on the toroid size.  Old-days coils
didn't use a toroid at all, but they gave shorter sparks, but they
were still tuned properly.  did you retune the primary when you
used the smaller toroids?  Did any of the small toroids have
the correct toroid shape i.e. a large radius of curvature?

What I really think is happening on your coil, is that the gap
is power arcing when you use too few primary turns.  It may
help to blow some air from a fan across the gap to cool/quench
it.  Just guessing.

Cheers,
John


>
> Isn't the toroid essentially a capacitor, necessary to tune the secondary to
> the primary frequency as well as to store energy, and as such isn't the
> toroid capacitance critical to the primary/secondary frequency "match"?
>
> The reason for the 2 foot toroid is that it gives biggest sparks - I have
> tried 4 6/8" and 5 7/8" toriods and even a 9" pie tin
> and all I have got are weak 1"-2" sparks to a sharply pointed object that
> was NOT grounded-
> the strange thing was that sparks drawn to a grounded object were shorter;
> was low-Q the likely culpit here?
>
> With 3 saltwater caps coil tunes at 4 3/4 primary turns -was 6 3/4 turns
> with only 2 saltwater caps
> this is to be expected as with MORE primary capacitance the primary will
> "match" the secondary with less primary inductance ie fewer primary turns-
> providing the secondary parameters remain the same, but If the toroid size
> were increased wouldn't the primary tap move back upwards- as secondary
> frequency would be lower and more primary inductance would be needed to
> match this?
>
> So if I add more capacitance to my primary won't I have to move the primary
> tap down unless I increase toroid diameter proportionately- that is, unless
> I add more secondary turns?
>
> ----- Original Message -----
> From: "Tesla list" <tesla-at-pupman-dot-com>
> To: <tesla-at-pupman-dot-com>
> Sent: Sunday, June 09, 2002 4:03 AM
> Subject: Re: Reducing toroid size
>
>
> > Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> <FutureT-at-aol-dot-com>
> >
> > In a message dated 6/8/02 8:19:11 PM Eastern Daylight Time,
> tesla-at-pupman-dot-com
> > writes:
> >
> > You're not really getting any benefit from the bicycle wheel.
> > You can simply replace it with a smaller toroid and get the same
> > or better results.  You could put a sphere about 4" dia on top
> > of the secondary and get a good result.  or a toroid that is about
> > 2" x 6" or 2" x 8" something like that.  You can just retune
> > the primary (change the tap point) to keep the coil in tune.
> > You may need to install a breakout point or bump on the
> > toroid to permit breakout, depending on its radius of curvature.
> >
> > If you make the new secondary with thin wire, it won't tune
> > at the same primary tap point even with a small toroid.  I'd just
> > leave the secondary as-is for now, and just install a smaller
> > toroid.
> >
> > John
> >