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Re: argh -- poor output on TC #2

Hi Stan,

At 12:29 AM 12/13/1999 -0500, you wrote:
>Hello all, I have finished my TC #2.  This one is 30.5 in of 22AWG wound
>on 6" drain pipe.  Toroid is 6"x20".  Right now I'm using 3 15/60s and
>an EMMC at 22.5 nF.  Primary is .25" cu tubing spaced .25".  Using the
>original Victoreen ceramic gaps from my old coil, I get 45"+ which
>rapidly diminishes because (I'm assuming) of too much power and
>overheating for those gaps.  So, I put together a 'blast gap'.  I used
>some L-shaped pieces of aluminum and ran stainless bolts through.  I
>epoxied an appropriate PVC reducer about .25" from the gap and plugged
>my shopvac hose in.  In short, the gap was horrible--I'd say 20" of weak
>streamer.
>
>So my questions are:
>
>1) Anyone else used the Victoreen gaps at medium power levels?  How good
>are they compared to other possibilities?  Why was my blast gap giving
>such poor results or is it really that lousy of a gap?

About half of the power that goes into a Tesla coil goes into heat at the
gap.   The Victoreens were probably quickly overheating.  Your blast gap
appears to not be working well at all.  I should point out that I use 27nF
with only one 15/60 NST so maybe you could use a lot more capacitance on
the primary too.

>
>2) How much would a SRSG help output? 45" seems poor given the amount of
>power I'm dumping in.  What else would those with experience with
>various gaps recommend?

Get a nice rotary sync gap going.  I have played with all kinds of gaps but
the sync rotaries are far far better than any others.

A quick option is also the multigap as in the following:

http://www.peakpeak-dot-com/~terryf/tesla/misc/terrygap.jpg

>
>3) I know for my 3 15/60's I should be using aroun 30nF to be mains
>resonant.  Would I be better off removing one of the NST's to get close
>to mains resonant with 22.5 nF?

I would remove two of them.  With three the gap is probably firing much
higher than 120 BPS which is probably burning up the spark gap.  Whatever
you do here, be sure to have good safety gaps across the neons.

>
>4) Would it be unusual for a coil like mine to have a large tuning
>range?  It seems quite content from about 9.5 turns up to 11.  My old
>coil had maybe a 1/2 turn range where output seemed to peak.

That is probably normal.

>
>I have noticed that this coil also seems much less drawn to typical
>strike objects.  For example, it seems happy to have its streamers go an
>extra 6" to hit wooden shelving than to hit a grounded wire with a
>pointy tip.

At high voltage the humidity in the wood may make it very conductive.  The
electrostatic fields around the shelf seem to be more attractive to the arc
than the wire which is odd but it all depends...

>
>Am I missing something?  I know I'll probably never match the efficiency
>of aces like Terry but this is pretty bad!

The rotary gap and matching the caps to the transformer(s) are the keys here.

There are a bunch of pictures of mine at:

http://www.peakpeak-dot-com/~terryf/tesla/misc/RGAP.ZIP

The instructions to modify a motor for sync operation are at:

http://www.peakpeak-dot-com/~terryf/tesla/misc/syncmot.zip

Don't worry too much about fancy machining on the motor conversion.  With a
1800 rpm motor, I used a hand grinder and it works just fine as long as you
try to remove equal metal.  I also cut the rotor by hand which seemed
pretty good but I later trued in on a lathe.

Cheers,

	Terry

>
>Help! :)
>
>-Stan
>