Re: soda bottle caps

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

Original poster: "kim fulk by way of Terry Fritz <twftesla-at-qwest-dot-net>" <kimisaliam-at-hotmail-dot-com>




>From: "Tesla list" <tesla-at-pupman-dot-com>
>To: tesla-at-pupman-dot-com
>Subject: soda bottle caps
>Date: Sun, 26 Aug 2001 23:03:28 -0600
>
>Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" 
><Cydesho-at-aol-dot-com>
>
>I know that this will seem primitive compared to the MMC's that everyone is
>building now, but I thought I'd ask about it.  I was wondering if anyone 
>out
>there has had any success with building bottle caps out of the two liter 
>soda
>bottles. I decided to build one and I found that it had a capacitance of
>about 400 picofarads. It also withstood being hooked across my 12 kV NST.
>Does anyone have any information about this, like the dielectric properties
>of PETE plastic. It's nice to have the list back.
>                                     Justin
>
>
>Hi Justin

My name is Kim and this is the first time I answer anyone on this list.  I 
usually read everyone elses messages,  but this time i wanted to answer 
yours.  I guess im shy,  anyway I have played with 2L soda bottles made of 
PETE to build NaCl solution and Al foil capacitors.  Referring to a web page 
on the electrical properties of plastics  I think this is very similar to 
Mylar plastic (if im wrong please correct me anyone on list).  The 
information i found for PET which is Mylar , has a listed dielectric rating 
of 7.5Kv/.001" and a dielectric constant of around 3.0 -at- 1MHz and a 
dissipation factor of.016 -at- 1MHz which is quite close to tesla coil 
frequency range operation (XXKHz-1MHz) roughly,actually  dielectric const. 
and dissipation factors due differ depending on the F but this should be 
roughly close anyway.

The capacitors I built for my 4.5"dia. coil were originally made of 2L pepsi 
bottles,  they roughly measured 2.1nF each using my 87 series fluke meter 
for measuring C, so i think this was fairly accurate measured value.  I ran 
my coil on 4 of these parallel for a total of around 9.95nF.  I ran the coil 
using a 9Kv .03A neon and it produced discharges of around 8 inches.  When i 
stepped up to 15Kv-at-.03A things started to change i was blowing my pepsi 
bottles left and right.  Anyway things started getting messy with salt 
water,  i decided that i would have to run then in series to lower the 
voltage across each bottle but then things started getting really bulky lots 
of bottles.  They due work but i found out they tend to break down in the 
15-20kv region also the bottoms of the bottles have scrapes and scratches 
which can lead to lower punture voltages, Also mylar tends to heat up at 
tesla coils F operation so this may lead to breakdown also.  Since ive 
switched to MGD beer bottles  which have given me better performance 
although they are glass(lossy also,  these bottles are clear and smooth and 
smaller my beer bottles measure roughly 1.1nF and are easier to move around 
than those 2L soda bottles and i can parrallel these bottles and they tend 
to with stand 15Kv RMS or 21.2Kv peaks and maybe more but not much i 
estimade maybe 25kv+???  With 20nF and 15Kv .06A (2 neons paralleled im 
getting 36" discharges from my 4.5"o.d. 22awg wound with 806 counted turns 
of essex magnet wire.  My spark gap is a air blown static gap made of 1" 
bronze pluggs pollished  and fitted to 1"copper pipe for heat sinking.  
Primary is 14 turns of.25" copper fridg. tubing wound in a flat spiral.  
Eventually i think il go mmc when i hit the lottery!  till then my piggy 
bank will have to fill up slowly.

Anyway my experience with PETE caps led me to try glass bottles mainly for 
the low break down voltages i was experiencing,  the beer bottles i like a 
lot better and they seem to perform well for me,  I talked to another coiler 
off list and he told me that his 42nf glass bottle bank produced similar to 
his 40+nf mmc bank.So glass bottles wine, beer etc are a nice alternative to 
costly caps if its out of your range for the moment. Its all about having 
fun so keep on expermenting thats the fun of it, if your like me, Who knows 
you might come up with a technological breakthrough just by way of 
expermentation.




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