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Re: More Beginner Tesla Questions (fwd)



---------- Forwarded message ----------
Date: Sun, 10 Oct 1999 11:15:12 -0700
From: Jim Lux <jimlux-at-jpl.nasa.gov>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: More Beginner Tesla Questions (fwd)


> Date: Sat, 9 Oct 1999 10:21:24 -0500
> From: Spud <spud-at-wf-dot-net>
> To: Tesla Coil Webring <tesla-at-pupman-dot-com>
> Subject: More Beginner Tesla Questions
> 
> Hey, I just need to get a few more questions answered before I get all my
> parts and start constructing my own Tesla coil.  First of all, is the
same
> wire that is coiled around the secondary connected to the torus on the
top,
> or does the torus just sit there and draw electricity somehow from just
> sitting there? (May be a stupid question, but hey, if the primary drives
> the secondary with no hard wiring, maybe the secondary has the same
effect
> on the torus. :)

You DO need to connect the top of the secondary to the torus.  Most people
space the last few windings of the secondary out and transition to some
sort of bolt on the top of the form (you've got to hold the toroid on
somehow).



  Secondly, how am I going to coil that tubing for my
> primary into a neat little conical spiral? (Or is there an easier or more
> effective way to do it?) 

Necessity is the mother of invention, and from my own experience, making a
nice conical spiral is a mother of a problem... That's why I used a flat
pancake primary.  Cones look neat, but I don't think they work any better
or worse than a flat spiral, or if you MUST have more coupling, a
spacewound helical primary (i.e. a solenoid). Flat spirals are bad enough..

How to do it, though... The easiest way is to get 4-8 supports that are
triangular, and cut notches in them at the right point for the winding. 
Say you had 4 supports, and you wanted the turns 1/2" apart.  Cut notches
at ( 3", 3 1/2", 4, 4 1/2...) on the first one, (3 1/8, 3-5/8, 4-1/8, ....)
on the second, (3 1/4, 3-3/4, 4-1/4, 4-3/4,...) on the third, and (3-3/8",
3-7/8", 4-3/8", 4-7/8"... ) on the fourth.  (i.e. move out 1/4 of the
distance on each one.  Then, lay your wire into the notches...

Foamcore works fine for a prototype coil, as does bare #12 or #14 house
wire (get some scrap and a razor blade and strip the insulation off).

Take a look at http://home.earthlink-dot-net/~jimlux/tc.htm for some pictures
illustrating this... 

The spacing isn't critical, nor is the appearance.. Once you've done it a
few times, you'll start thinking of better ways to do it..  In the mean
time, avoid "analysis paralysis" and just build the darn coil....improve it
later.



 Another thing - aren't we concerned about the
> sparks from the torus tracing back and striking the primary?  If so, why
> would you construct the primary right there around the base of the
> secondary, about 2 feet from the toroid, with no cover or anything?

You bet this is a problem... Tesla coils are always a balance between
getting the sparks to go where you want, and getting long sparks...

You can put a "strike rail" around the top of the primary.. It's a grounded
conductor going most of the way around, spaced slightly above the primary.
Don't make it a complete turn, though (or it acts like a "shorted turn" on
a transformer, and sucks up a lot of power)...

> 	
> 	Thanks,
> 	    Ryan
>