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Tesla Coil questions from a beginner (fwd)





---------- Forwarded message ----------
Date: Sun, 17 May 98 22:09:31 EDT
From: Gary Lau  17-May-1998 2159 <lau-at-hdecad.ENET.dec-dot-com>
To: tesla-at-pupman-dot-com
Subject: Tesla Coil questions from a beginner

>From: Bob <bob985-at-earthling-dot-net>
>To: tesla-at-pupman-dot-com
>Subject: Tesla Coil questions from a beginner
>
>I am new to the list and the hobby of building Tesla coils.  I was
>hardly aware this kind of hobby existed several months ago, but now am
>*very* interested.  :-)
>
>
>I have learned a lot by browsing web pages and by reading the postings
>in the last few weeks, but  I still have many questions.
>
>
>Basically, on my first coil, I want to get somewhere from 12-24 inch
>sparks, but can't  have more than 24 inch sparks due to safety concerns.

I've found that it's pretty hard to stop at any predetermined point ;-)
A matter of self control...

>
>I plan to use a section of dryer venting for the toroid, make the
>capacitors out of glass bottles,  and have the secondary somewhere
>around 24-30 inches tall.
>
>-What are the advantages/ disadvantages of using 36 vs. 26 gauge wire
>for the secondary?
>I am assuming that with the 36 there would be more windings, and
>therefore a higher output voltage and longer sparks. Is this correct?
>
>Would a section of 4 inch diameter tubing be better than 2 inch diameter
>
>tubing for longer sparks?

The ratio of secondary height to width should not be greater that about 5:1 or
so.  Use a 4 " wide coil, with 20-24" length.  A two inch coil is too thin for
anything that you are shooting for >12" from.  Number 26 wire would be a better
choice.  It will have a lower resistance, which will result in a higher
secondary Q, which will result in a higher resonant voltage rise in the
secondary.

>Generally, what output would I be looking for on a transformer?
>(6-15KV?, 30ma, 60ma+?)>

You should be able to get 12-24" on a well designed coil with a 12-15KV, 30mA
transformer.  60 mA units are extremely hard to find, seems no one uses them
anymore, while 30 mA units are quite common.  The 15KV jobs may be a bit harder
on caps though.

>How much improvement would a RQ spark gap show over a spark gap made of
>angle irons and bolts? Would this be overkill for a coil this size?

I've heard only glowing testamonials for RQ gaps being so much better than
bolt-type gaps and have not used anything else myself, though I am working on a
rotary gap now, but that's another story.

>What kinds of wire would I use to supply the power to the primary?
>(maybe) Over a cement floor?
>Neon sign wire? Regular 12 gauge wire in electrical conduit?

I assume you're talking only about the wire from the transformer to the main
spark gap (and not the primary tank circuit).  Use neon sign wire if it will be
draped over the floor or touching any other wires.   But FWIW, my unit is all
contained on a plywood base and the leads are short and direct enough that any
kind of wire could be used.  Compact is best, especially in the tank circuit.

>Will running this in a garage just below a computer and dozens of 3.5
>diskettes do nasty things to the circuitry and/or data stored?
>Will I have to build a Faraday cage?

I don't think the diskettes will be affected.  However, the computer may be.
Unplug the computer and printer and monitor, and Most Importantly, unplug the
phone line going into the modem!

>Essentially, what would give me the 12-24 inch sparks for the lowest
>cost?
>
>
>Thanks for any questions you might answer.
>
>
>-Bob

You're welcome,
Gary Lau
Waltham, MA USA