Re: A newbie question

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

Original poster: "Antonio Carlos M. de Queiroz" <acmq-at-compuland-dot-com.br> 

Tesla list wrote:

 > Original poster: "Gergely Nagy" <gergely.nagy-at-bluewin.ch>

 > So, I've read the description and construction notes of George Trinkaus on
 > the TC and I would like to build one too. I went to hardware stores to look
 > for materials, but even to find pipes for the primary and secondary would
 > be a problem. George in his description goes with a 3.5" x 18" secondary
 > and a 7" x 5.75" primary. And this is what I can't find.
 > So I thought I might reduce the sec. and the prim. to one half.

Make a flat coil for the primary. A solenoid complicates access to the
coils and can easily lead to sparks between them.

 > 1. In this case, would the #28 wire be adequat for the task or should I
 > look for a thinner? Same question  for the primary's #8 stranded wire.

#28 looks ok. About 1200 turns. Solid wire is easier to keep in place
in the primary. The most usual is to use copper tubes, but for a small
coil there is really no need for this, except may be for mechanical
reasons. Electrically, even #18 wire works perfectly.

 > 2. Transformer-wise, the booklet suggests something between 6000 and 15000
 > V and 30 to 60 mA. I guess the transformer at the lower end would be
 > sufficient.

Yes.

 > 3. The other hardnut is the capacitor (as everywhere else). I found the
 > description of the beer-bottle capacitor in George's booklet and I think
 > it'd be OK to build it. There is just one thing which is not clear. So when
 > bottles are filled up and are in the "dishpan" and its filled up too to
 > within about 0.25" of the top, do you have to seal the "dishpan"?

No. The salt water is just to make the capacitor plates, saving you the
work of gluing metal foil to the internal and external surfaces of the
bottles. These salt water capacitors are just XVIII century technology
Leyden jars (before the invention of metal plates!).

 > Otherwise
 > if I got it right, the interconnected bottle terminals is one pole and the
 > metal inside of the "dishpan" is the other.   OR  Would you rather suggest
 > to buy the capacitor? Since it wouldn't be a big TC I am sure that I won't
 > need a 0.3uF 35Kv capacitor. How can I figure out what I need?

Make an MMC capacitor. A series-parallel association of several
commercial not-so-high voltage capacitors (1.6 kV). The value that you
need is the one that tunes the primary and the secondary systems to
the same frequency: L1C1=L2C2. Your C2 will be at about 20 pF, and your
L2 at about 25 mH. Assume an L1 of 33 uH, and C1=15 nF. Use one of the
several available Tesla coil design programs to choose the values,
and even the geometry of the coils before you start. My programs,
for example, are at http://www.coe.ufrj.br/~acmq/programs.

 > 4. Since I could get hold of as many plexiglas as I can, I tought I would
 > build a cage around the primary circuit for the sake of security. BUT would
 > plexiglas securize anything at all at these high voltages? Is wood any
 > better? And wouldn't heat evacuation be a problem? First I thought to put
 > everything but the coils under the cage but maybe spark gap should be left
 > in the open air so it can be cooled easily.

Just make the system so nobody will touch the dangerous areas and
everything is reasonably stable mechanically.
Use the acrylic to make a big static machine :-)

 > I know I got many things to learn but I am 100% motivated and I know I can
 > do it. Of course security is very important, so if there are some other
 > things I should know about (and what is not at pupman-dot-com on the safety
 > sheet) please tell me.

It's all there, but:
1) Don't touch the primary circuit (possibly lethal).
2) Don't touch the secondary circuit and the sparks (may cause burns).
3) Don't operate the system in a place without ventilation (ozone is
poisonous, and at least very irritant).
4) Be careful with the construction. It's far easier to be wounded by
the tools that you use to build the coil than by the coil itself.

Welcome,

Antonio Carlos M. de Queiroz