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Re: Wire Guage and Q?

At 09:26 AM 01/02/2000 -0800, you wrote:
>>snippp->
>Terry, and all who replied,
>
>My max output so far is about 8".  That was running with 15/30 input and 
>both of my appx. 5nf caps in parallel. The inner turn of my primary is about 
>10.5" and the outer is at 23.5".  Slope is 35.5 degrees. 5" tall. I wanted 
>2" clearance between the innermost turn of the primary and the bottom of the 
>secondary.  Havn't got any D'Arsonval breakdown yet!
>
>Also, I was a bit curious about the coupling.  I am not sure about how to 
>calculate the K coefficient.  I used the equation in The Tesla Coil Book, 
>and kept getting wierd numbers like 19.6...  I checked my work a lot too.
>
>I seem to get the best output when the bottom of the primary is slightly 
>above the bottom of the secondary, which I don't like.  I am pretty sure my 
>new rotary is synchronous, and I will hopefully try it out tonight.
>
>Unfortunately, I can't see really any point where the bolts on the rotor are 
>"repeated" when i look at it spinning under a flouorescent light.  It is 
>very obvious when I turn it off and it slows down past the other multiples 
>of 60.  It is 1800 RPM (at least I hope it is). Does the strobe effect work 
>better on a 3600RPM motor because it turns 60 times per second instead of 
>30?
>
>Thanks,
>
>Nathan

Hi Nathan,

With 10nF of primary capacitance and two NSTs (15kV/60mA total) you should
tap the primary at around 7-9 turns.  I would expect 30" arcs out of it...
 Check the following.

1.	I assume you have a dryer duct type of toroidial top terminal since you
have done everything else so well (you still didn't mention what your
terminal was ;-)).  You may try putting a nail or sharp point on the top
but that is probably not the problem unless you have a big smooth "real"
toroid.

2.	The rotary gap may be giving you a problem if it is not synced.  Check
that by putting bright florescent tape on it or dark tape(what ever shows
up the best) and running it under a florescent light.  You should see the
bright and dark areas (they will be fuzzy but stable).  When you turn off
the motor, those areas should instantly start to spin as they fall out of
sync...  I put a strobe disk on my rotaries to help me see this and adjust
the dwell (http://www.peakpeak-dot-com/~terryf/tesla/misc/strobe.gif).
However, any high contrast making will work here.

3.	This IS the problem if you haven't done it...  I assume you have turned
your gap motor back and forth so that you are sure the gaps are aligning at
just the right time.  If the gaps align at the 4000 volt point instead of
the 20000 volt point that could explain it all right there.  The gaps must
align just when the AC voltage reaches the highest point.  You need to turn
the gap motor (or whatever) to adjust the "dwell".  This is typically done,
by trial and error, by turning the motor body bit by bit through 90 degrees
(four electrodes) until the best spark is obtained.  If you motor is
salient pole, you can turn it on and off and it will always come back
faithfully to the same position.  If it is not, then the motor will have to
be adjusted each time it is turned on. 

4.	I would also check to be sure each leg of your two neons can draw an
arc.  If one of the neons has a dead leg, that will mess everything up.  Be
sure they are hooked up in phase too but if they weren't you coil would
probably not do anything (unless there is a dead leg).

5.	It is possible that the polyethylene cap is hurting performance too or
it has a failure in it, but check this other stuff first.

6. 	If your coil has a variac and control box, try running a big lamp on
the output just to be sure it is working too.  It is possible to wire
something wrong there that would be difficult to track down unless you
check it to be sure. 

7.	Be sure the base of the secondary is grounded and be sure the cases of
the neon transformers are too.  You may want to carefully go back and check
all that basic wiring stuff.  It wouldn't be the first time a problem coil
has had some very  simple wiring problem...

Something is really wrong somewhere but your coil's construction and all
that you have said about it sound great.  I am sure once we find the
problem it will work very well.

You can't calculate the coupling (K) by hand (I don't care what the book
says ;-)).  You can measure it but your coil should be just fine.  If it
gets racing arcs once it is working, then will worry about it...  I would
set it at the place that gave you the best performance before as you mentioned.

Cheers,

	Terry