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Re: Re Basics


From: 	Julian Green[SMTP:julian-at-kbss.bt.co.uk]
Sent: 	Friday, August 01, 1997 11:56 AM
To: 	tesla-at-pupman-dot-com
Subject: 	Re: Basics

>Greetings from Australia!  I have been "lurking" in the background for a while
>and I must say this is a GREAT list!  Very informative, but a fair bit is
>rather advanced for me at this stage, as I have yet to build my 1st Tesla coil.
>Would appreciate it if someone good guide me on where to start in the midst
>of all this excecellent technical information. I guess I should start on
>something of lower voltage and ease of construction 1st.
>Then advance to the "power user" class later!    :-)

Starting on lower voltages is slightly safer but by not much.   Getting a zap
from a charged 0.02uF capacitor at 8KV could to be fatal.  Make sure you 
discharge your caps before you make adjustments.

Don't go for a small coil.
Small coils have a high resonance frequency and good sparks are difficult
to get at these frequencies.  All you get is brush like discharge and loads of
ozone - you will have to evacuate the room very soon after.

>From other posts on this list a 4" coil sounds good although my first coil
was 7" diameter wound on plastic gas pipe and this has worked very well
at low power and also at higher powers.  Its resonant frequency is 170KHz with
24" toroid and spark production is good.   I was able to generate 6" sparks
on only 1.5Kv primary voltage.  I now get 45" from the same coil running at 
11Kv and 3KVA.

You want to aim for about 900 turns of wire on the secondary.  Chose wire
size so that the winging length does not exceed 4 times the diameter.

Make the primary from copper pipe, refirgeration tube is good, but quite 
expensive.  Coax makes a cheaper alternative remember that skin effect comes
into play here so thin wire is no good - use the braid.

Make your cap from clear or slightly coloured polyethelene (not black) and 
cooking foil.  I built a 0.03uF cap this way, didn't bother with oil and 
had no problems, voltage was 8KV and run times were short. 

Spark gap made from coins mounted on screws to allow adjustment.  At low 
power the quenching was good, but higher power this is useless.

Make sure that you have a seperate RF earth which you connect the base of
the secondary.  Do not use the house earth as you will get the RF from your
coil going every where.

Check out http://www.eskimo-dot-com/~billb/tesla/tesla.html

Hope this helps
Julian Green