Re: 60 vs. 30 ma - charging

From: 	Bert Pool[SMTP:bertpool-at-flash-dot-net]
Sent: 	Monday, June 30, 1997 1:55 PM
To: 	Tesla List
Subject: 	Re: 60 vs. 30 ma - charging

> From: 	Pete Demoreuille[SMTP:pbd-at-cybernex-dot-net]
> Sent: 	Thursday, June 26, 1997 9:36 PM
> To: 	Tesla List
> Subject: 	Re: 60 vs. 30 ma - charging

> On another note:
> I have almost finished my first coil:
> powered by a 15kV neon -at- 30mA
> Caps:  two crates of 14 snapple bottles each, each crate rated at 11uF, 
> 	which are connected in series to give around 5.5uF of capacitance

Those must be the giant 100 gallon Snapple bottles!  Perhaps you 
meant 5 and 11 nanofarads?

> One single spark gap made with 2 carriage bolts, housed in a box with an
> 	exhaust fan at one end.

You really need to make an RQ gap, or at the very least, make a 
simple gap out of a dozen or so copper cylinders mounted 
side-by-side.  A single gap make from carriage bolts will quench very 

> Primary is 12 turns of 1/4 inch copper refrigerator tubing, at a 30
> degree
> 	angle to make it ~4in high and 11in radius.

11 inch radius or 11 inch diameter?  A primary for a coil this size 
which is 22 inches in diameter seems a bit large.

> Secondary is ~450 turns of plastic insulated wire, (couldn't find any
> enamled,
> 	i am working on it) for a total wrapping length of 21.5in
> separation between primary and secondary is 2in

You're going to be mighty low in inductance with plastic covered wire 
unless you use a large diameter secondary.

Since you did not say how large your secondary is in diameter, I 
cannot calculate the inductance or resonant frequency.  Are you 
planning on placing a toroid on top, and if so, how large?   I'd 
guess that a 12 inch diameter toroid with a 3 or 4 inch cross section 
would work well with a coil in this power range.  

> Any suggestions, comments, improvements (I am sure there are many, I am
> working on getting some mica for making some real good plate caps, and
> making a better, closer secondary, and getting a new transformer)

Pete, mica has a poor dissapation factor for Tesla coil use.  
Polyethylene makes a far superior cap, and will cost you a 
tiny, tiny fraction of what mica will cost.  It is =very= difficult 
to find capacitor grade mica anymore, and it is outrageous in price 
when you can find it.

> Any clue how much separation the spark gap should have, and where i
> should tap the primary???  Please HELP!  I have not a clue.

If you'll provide =complete=  and accurate dimensions and values on 
all your coils, caps, etc., and toroid size, I or one of the other 
coilers on this list can give you a good ball park estimate for a 
starting tap on the primary.

BTW, a cylinderical gap allows you to simply clamp onto different 
cylinders to change the gap.  Typical spacing between gaps is very 
small - I normally space them about the thickness of a business card.

> If you could give a suggestion, that would be greatly appreciated,
> but if you could explain how you got the suggestion, that would make
> you a god.
> Happy Coiling!
> Pete Demoreuille

Good luck, Pete.

Bert Pool