Re: Newbie with questions...

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

Original poster: The MCP <ejkeever-at-comcast-dot-net> 

I've noticed two questions that came up that I didn't include. My original
topload was 4 1/2-inch copper elbow joints connected with pieces of copper
pipe about an inch long. Second, it's performance (based on what I've read)
is dismal; Currently, it shoots streamers out of three places: The end of the
top wire generates the longest, some small ones come out of the middle of the
little "topload" spiral, and a few more are generated by the last turn on the
secondary (???). The end wire streamer is about 2 inches long, and wavers
around a 30 or so degree cone.

Also, after finding that the resonant frequency is around the 700-800 Khz
range (High enough to cause the skin effect in a human), I've consistently
drawn sparks about 3 to 3.5 inches long off it with my fingers.

I think we can all agree that that's not what it should be :(. As Gary noted,
it's probably the tank cap. These are doorknob caps from TDK, each rated for
40KV (not likely to blow out on a 5KV rms transformer) and 2nF. I've got one,
with 2 more that should arrive by tomorrow. That should help greatly!

One more thing. I don't know how wise this was, but please don't hurt me :).
As I was intending this to be a sort of "demonstration" coil, that would get
moved around frequently, instead of attaching the bottom of the secondary to
a fixed ground, I put about 7 feet of wire on it and use it as a sort of
"wand." Since that end had no capacitive load on it, it currently does
nothing but form the faintest of coronas. 3 questions: Is this wise/ok/legal,
what effect will it have on coil performance (the coil does not arc any
farther to it than to my fingertip, if that helps), and is there any
substitute for an earth ground?

Thanks again!

On Thursday 11 September 2003 10:19 am, Tesla list wrote:
 > Original poster: "Harold Weiss" <hweiss-at-new.rr-dot-com>
 >
 > Hi MCP,
 >
 > It doesn't sound as bad as my first coil.  What is your streamer length?
 > As far as your second question, the coil of wire will have capacitance just
 > as the topload does.  It can be suprising how much capacitance that it does
 > have.  When I hooked up my electric waterfall the first time, I had to
 > retune the coil just to get it working right.  On the third try I shortened
 > the wire to it two feet, and that brought it back into tune.  The added
 > interturn capacitance of the coil is higher than when the wire is straight
 > out, thus bringing your coil back into tune.
 >
 > Welcome to the list, and may your streamers be long and plentiful!
 >
 > David E Weiss
 >
 >  > Original poster: The MCP <ejkeever-at-comcast-dot-net>
 >  >
 >  > Hello, everyone. I just signed up and have some questions to ask about
 >
 > some
 >
 >  > aspects of coiling.
 >  >
 >  > I've built a small (tabletop-size) tesla coil for fun, and I am
 >  > observing
 >
 > some
 >
 >  > very odd behavior from it. But first, I should provide some basic info.
 >  >
 >  > The secondary is a .75" PVC pipe (I got excited and built it before
 >  > doing enough research), with about 10.5 inches of 32 gauge magnet wire
 >  > on it,
 >
 > about
 >
 >  > 1000 turns. The helical primary is 5 inches in diameter, ~3.5 inches
 >  > tall, with 5 turns.
 >  >
 >  > The main tank circuit has a smallish 5000/20 NST and currently a single
 >  > 40KV/2nF cap from TDK that I picked up for $30.
 >  >
 >  > The spark gap is a simple static gap, currently separated by about .125
 >  > inches, using the tips of a pair of screws. When these wear out, I can
 >
 > just
 >
 >  > replace them with fresh ones. The gap can be set for up to 1/2 or so
 >  > inch separation.
 >  >
 >  > Currently, the whole thing is in a highly experimental state. By that I
 >
 > mean
 >
 >  > that very little is set in stone; Almost all the major connections are
 >
 > either
 >
 >  > twisted together or clipped. So you've got a lot of latitude to change
 >  > things.
 >  >
 >  > Anyway, on to my questions. First of all, I'm wondering if I've got any
 >  > of
 >
 > the
 >
 >  > components grossly off-key. Comment away.
 >  >
 >  > Second, I've found something odd( to me at least). One day, just for the
 >
 > heck
 >
 >  > of it, I took off the topload and stretched the wire straight out.
 >  > Nothing much happened. But when I took the 6 inches or so of wire and
 >  > wound them
 >
 > into
 >
 >  > a small spiral (about 7 turns, 3/8 inch diameter, 1 inch long), the coil
 >  > worked almost as well as with the big copper topload so I abandoned it.
 >
 > Can
 >
 >  > someone tell me why?
 >  >
 >  > Thanks for taking the time to slog through all this and answer my
 >  > probably silly questions!