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RE: [TCML] Newbe's First Coil
Google "beer bottle capacitors"
Large and messy but bulletproof and right at the value that you need.
Dave
> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx
> [mailto:tesla-bounces@xxxxxxxxxx] On Behalf Of Lau, Gary
> Sent: Sunday, January 31, 2010 1:17 PM
> To: Tesla Coil Mailing List
> Subject: RE: [TCML] Newbe's First Coil
>
> Hi Charlie,
>
> I agree with all that Matt suggested.
>
> Additionally, I suspect that your caps may be a problem.
> Ceramic caps have a very high temperature coefficient,
> meaning that their capacitance will vary as a function of
> temperature. So the primary tuning will rapidly drift as it
> runs, and won't be in tune with the secondary. I'm not sure
> that blowing air on the caps will help; if the exterior is
> getting warm, the interior will be MUCH warmer. Funny that
> only one gets warm though!
>
> I don't see a problem now but this is something that may need
> to be said. It may appear that performance increases as you
> increase the gap spacing. You must resist the temptation to
> do this, as having it too wide will allow voltages in excess
> of what the OBIT can endure to develop.
>
> Regards, Gary Lau
> MA, USA
>
> > -----Original Message-----
> > From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> > Behalf Of mddeming@xxxxxxx
> > Sent: Sunday, January 31, 2010 3:36 PM
> > To: tesla@xxxxxxxxxx
> > Subject: Re: [TCML] Newbe's First Coil
> >
> >
> >
> >
> >
> > Welcome Charlie,
> >
> > ANY coil that works on the first try IS a success!
> >
> > Here are a few simple suggestions that might improve your results:
> >
> > 1) The pizza pan/ cookie tin combo is a problem. The thin
> edge of the pan, and the
> > sharp edges of the tin allow charge to bleed off, reducing
> peak voltage. The fatter
> > and more rounded edge of a toroid allows more charge
> build-up. A piece of
> > aluminum dryer duct or foil-covered Styrofoam doughnut will
> serve you much
> > better.
> >
> >
> > 2) Your spark-gap definitely has heating problems. If you
> are not yet going to use a
> > multi-gap, then at least do the following:
> > (a) Use heavier, brass, round-headed bolts or threaded rods
> with brass balls. Brass
> > conducts heat and electricity better than steel, and larger
> terminals mean better
> > heat dissipation. Rounded terminals mean less corona loss.
> > (b) Put a fan or other blower on the gap. Hot, ionized air
> in and around the gap
> > causes it to fire sooner preventing full charge build-up.
> > (c) Slightly reduce your gap width. 5-6 mm (1/5 to 1/4 in.)
> will prevent a misfire from
> > overvolting your transformer and your caps.
> >
> > 3) Make sure that none of your OBIT HV connections are
> mounted directly into
> > wood. Even at only a few thousand volts, wood starts to
> become progressively
> > conductive becoming both a power drain AND a fire hazard.
> Use ceramic or HDPE
> > insulators to support the gap and all HV wiring.
> >
> > 4) Blow air onto your caps also. As they warm up, they
> change value and spoil the
> > tuning, even if the heat doesn't damage them.
> >
> > 5) It is not clear how or what you are using to keep your
> primary turns properly
> > spaced. Also, make sure your tapping clips are not touching
> / arcing to the turn
> > below.
> >
> > These should be relatively inexpensive and quick
> improvements without having to
> > rebuild everything. Let us know your progress.
> >
> > Matt D
> >
> >
> > -----Original Message-----
> > From: cbroring@xxxxxxx
> > To: tesla@xxxxxxxxxx
> > Sent: Sun, Jan 31, 2010 1:21 pm
> > Subject: [TCML] Newbe's First Coil
> >
> >
> > Hello to the members of this list. For no particular reason
> I built a Tesla Coil this
> > winter. Just got it running, more or less. So (hopefully)
> here are a couple of photo's
> > of what I put together.
> >
> > http://img651.imageshack.us/img651/5567/1000420.jpg
> > http://img683.imageshack.us/img683/5931/1000424e.jpg
> > http://img651.imageshack.us/img651/5043/1000425.jpg
> > http://img651.imageshack.us/img651/5164/1000427.jpg
> >
> > The transformer is a 10kv 23mA oil burner trans. Primary is
> about 12 turns # 14
> > sold house wire 10" diameter with a couple extra taps
> available. Secondary is 1300
> > turns #27 on 3.5 inch pvc. Spark gap is 2 nails spaced
> about 5/16" Capacitor is two
> > 6000pF 30kv hokey puck ceramics, and one shows a slight
> temperature rise with
> > use. Top load is a cookie tin and bent pizza pan. The
> ground is the house wiring
> > tied in to an extensive ham radio/ lightening ground system.
> >
> > It really doesn't work that great. I removed a coupe turns
> and moved the tap around
> > to get the best coupling I could. I get a ring of 2 inch
> sparks of the pizza plate. I put
> > a screwdriver on top and get 3-4 inch sparks off that. I
> haven't tried bringing a
> > grounded probe to the top load yet. Anyway, I read that the
> ceramic capacitors are
> > not really durable and one of mine shows some heating after
> a minuet or so of on
> > time to. I think I need to work on that next. I expected a
> little more out of it even with
> > the 250 watt power transformer.
> >
> > I need to figure out how to ground the thing. I need a
> better capacitor. I have lots of
> > big transformers and DC power supplies to play with once I
> get the coil working a
> > bit better.
> >
> > Any suggestions are much appreciated.
> >
> > Charlie
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> >
> >
> >
> >
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