Re: Am I missing something here?...

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

Original poster: "Malcolm Watts" <m.j.watts-at-massey.ac.nz> 

On 2 Nov 2003, at 12:37, Tesla list wrote:

 > Original poster: The MCP <ejkeever-at-comcast-dot-net>
 >
 > Alright, I've setup the coil as described and even though I've confirmed
 > through an oscilloscope that it's resonating, I still get nothing even
 > beginning to approach the claims that it will shoot 17 inch sparks.

I wonder who claimed it would do that with the cap/transformer combo
you're using??  Some back-of-the-envelope calculations reveal why it
won't:

Cap size - too small by a factor of 2.5 to resonate with the
transformer to deliver at least 260 - odd mJ. The best you can expect
with 4nF and not setting the gap beyond transformer-destruction point
is about 100mJ - far too little energy to do the job.

     A 10nF cap would be better suited and better still, about 15nF
which would get your primary energy to around 370mJ. Still not a lot
but you might get to 1ft with a bit of luck.

Malcolm

 > I've the the 5000/20 NST attached to two 2nF/40Kv doorknob caps in parallel,
 > for a total of 4nF. From there, I have a single static spark gap which 
is two
 > .5 inch copper pipe elbows which are basically impaled on screws and
 > rotatable, and the primary coil which is 4 turns of .25 inch copper tube,
 > with turns averaging 1 to 2 inches apart (It's a little messy right now, 
just
 > sitting on the floor bare) which tunes when tapped around 2.5 or 3.5 if 
I add
 > the third doorknob cap (Whew - I'd get marked down for a runon if this 
were a
 > test).
 >
 > The secondary coil is 26 gauge copper magnet wire wound around a 3 inch ABS
 > plastic form, about 18-20 inches wound. One side is connected to a wire
 > running to an earth ground, which is a steel rod pounded about 1.5 feet into
 > the ground, the other (since I don't have any real topload) is ~10 inches of
 > wire from the end, wound into a little coil .75 inches in diameter.
 >
 > This arrangement produces streamers going about 3 inches into the air, and
 > going maybe another half inch to anything you get close enough. I haven't
 > taken exact measurements, but it doesn't take a ruler to realize that this
 > coil is NOT generating foot-long sparks.
 >
 > Where am I going wrong? Do I need to ground the primary equipment to the 
same
 > earth ground as depicted in some schematics?
 >
 > On a rather ridiculous side note, what would happen if one were to take the
 > 5000 kilometers of wire necessary to make a coil that would have a natural
 > resonant frequency of 60Hz and drive a primary by simply hooking it directly
 > into the mains? Or if you were to go a step further and connect it to the
 > cross-country 340Kv lines?
 >
 >
 >