My Neice's new coil...
From: Rodney Davies[SMTP:rgd872-at-anu.edu.au]
Sent: Monday, July 14, 1997 7:04 AM
Subject: My Neice's new coil...
About 2 weeks ago I posted information regarding a design of a 4" coil I
was going to build for my Neice's High-School Science project, and
thank-you all for for responses and positive support! :-)
Anyway, I went up to Brisbane (from Canberra) on the 2nd of July and I
started construction on the 3rd of July. Finished it the
following Thursday...it took exactly 1 week!
The coil was a success... produced 12" sparks from a 10KV 30mA neon
xformer! Mind you, it still hasn't been tuned properly yet..I ran out of
time...I'm now back in Canberra...
Anyway, here are the specs -
4 3/8" diameter PVC pipe. Prepared by coating it with one-pack
#22 Wire guage enamel coated copper wire (0.63mm), Close Wound.
Winding length: 22" (For some reason, I managed to get 880 turns...???)
I coated the windings with the polyurethane with only 1 relatively even,
thick coating....(talk more later on operation)...
12 turns of 1/4" copper pipe spaced at 1/4" between turns in a flat
pancake archimedes coil.
The spacing between the primary coil (1st turn) and the secondary is 1".
0.01uF 20KVDC paper rolled capacitor (originally taken from a RADAR).
Richard Quick style quenched spark gap with 7 electrodes spaced at approx
2.5-3 millimetres. (only eventually ended up using 2 gaps).
Works very well too!
10KV 30mA Neon xformer.
The operation of the coil went quite well.
Initially I started out at 12 turns, obtained roughly 3" sparks...
Reduced the turns down to 8 and got 12" sparks.
Also, one thing I shall note is the loudness of the spark gap and
secondary output during tuning.
I read previously a month or 2 ago where coilers stated that when a coil
is getting closer to resonance, the spark gap tends to be much quieter
than the secondary. This case is true. I found when I was way-out of tune,
the spark gap roared, however, when I started to approach the resonant
point(s) the secondary became much louder...
Well, one can say that is obviously due to more output by the secondary,
but it's a good indication of tuning...especially with small coils.
Well, as the story continues, I did a few neat little things like holding
an incandecent clear bulb in my hand about 2 feet away from the coil and
watching it spark like a plasma ball! Also the case of having other coils
nearby arcing from the field(s) etc...
Tried to do the wireless transmission of electricity concept by
overloading the top secondary terminal preventing spark, and having a
different "free" coil nearby connected to the same RF ground and found
that it arced quite nicely...
I then built a small faraday cage for it to be contained so that curious
fingers can't get hurt. The coil immediately de-tuned (obviously), but I
have told my neice to re-tap out at 12 turns instead of 8 increasing the
primary inductance which should hopefully counter-act the added
capacitance of the cage...
Anyway, from here my Neice's tesla coil is going into a school project
competition where lecturers from the University of Queensland and CSIRO
are going to be judging them under various categories, most of which the
TC seems to be able to fall under nicely!
The concept my neice is demonstrating is the wireless transmission of
electricity....hopefully that should impress the judges since we have got
it setup to do that....I think... All of the idea was based on experiments
that R. Quick had done in the past...
Well, the Judging is this Thursday coming, I'll hear about it on Sunday
and let you all know of her success..!
Well, if you have any more questions, ideas, etc....whatever, please bring
Thanks Everyone for your help, and hope you enjoy hearing yet another TC
success story! :-)