Re: Model T First Light

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

Original poster: "Gregg Adams by way of Terry Fritz <twftesla-at-qwest-dot-net>" <network-at-intop-dot-net>

Hey dave,
    I fought with my coil for a while with this really pretty spiral that I
made by spec and expected great performance but no such luck even after
tuning.  I grabbed up some spare copper that I had lying around and
free-handed a helix of 12 inch diameter and 6 turns(looked like crap).  This
is on a small system that only has a 4 inch diameter secondary and 15/60
nst.  I was getting 3 to 4 inch streamers at best with the spiral.  When I
switched to the helix, I was getting 12 to 16 inch streamers.  I still can't
figure out why mine is having coupling problems with a spiral but I'm
staying with the helix till I have trouble with some arcs between the
primary and secondary.
    About the amount of turns... I am using 1/4 inch copper tubing with 1/4
inch spacing between each turn.  If you are using the same then the 58 turns
doesn't sound right.  That would make the helix primary close to 30 inches
tall!!!  I guess it all depends on what your system specs are but that would
be a big primary.  Mine is 9 turns and tapped at 5.  The only reason I used
nine is cause that was all the spare copper I had left and it was just an
experiment(not calculated).  I like the helix better anyway cause it's more
compact unlike the platform for the spiral I made which was 2 foot diameter.
Just a little feedback from a newbie:)

            Hope this helps!
            Gregg





----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Thursday, March 14, 2002 11:13 PM
Subject: Model T First Light


> Original poster: "David Kyle by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<dave-at-kyleusa-dot-com>
>
> The new caps came in and with a few modifications I got them fitted to my
> battery powered Model T spark coil powered Tesla Coil. I put the two
> doorknobs in series for a value of 1000PF at 80KVDC (well at least the
caps
> should never fry from over voltage!). I fired it up and with a few
> adjustments to the spark gap got consistent firing with about a 1/8 inch
> gap. Being totally out of tune I did not expect much but was pleasantly
> surprised when I could draw 1/2 inch sparks from the top load. No breakout
> but it did light a florescent tube a few feet away.
>
> This seems entirely consistent with Ed's results from several days ago. It
> also suggests my original problem was in fact way too much capacitance for
> such a low powered coil. At .01uf I was effectively showing the spark coil
> a short. In fact 1000pf is probably the maximum this one can go and a
wider
> spark gap could no doubt be had at 500pf.
>
> Now to tuning and primary geometry:
>
> I am going to have to rebuild the primary since I had never planned on
such
> a small cap and have far too few turns to get it in tune. At present it is
> a 45 degree conical primarily because I couldn't decide between a spiral
> and a helix (it seemed a good compromise at the time and it does look cool
:-).
>
> Since I probably need all the coupling I can get, I am now leaning towards
> a helix. What say you all, spiral or a helix?
>
> The only downside that I can see to a Helix is that it takes far more
turns
> to tune with a helix. Using JavaTC I find I need 26 turns with a spiral
and
> 58 turns with a helix. Does this seem correct and why?
>
> Thanks again for all your help,
>
> Dave
>
> =========================================
> Dave Kyle
> Austin, TX USA
> Email: dave-at-kyleusa-dot-com
>
>
>