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Re: [TCML] dc tesla coil

Thanks John for your help.  I finally found a few details on the rotary gap
and dc coils by searching this forum.  Also spent hours searching by google
only and did not find much.  I've been looking over all of my old Tesla
components and have found almost every part I need less a small
storage/filter cap.  I do have two 70mfd/10kv very large and heavy caps
that could be used, however when I was using one of these brutes in a coin
shrinking circuit every time it fired it sounded like a 12g shotgun going
off.  Made me real nervous and sent my shop cats into hiding.  I have a two
pole pigs, several nst, high voltage heavy plate transformers to choose
from so charging the 70mdf cap is not a problem, however some what slow in
bringing the up to voltage for the first time.  I have more stuff to search
through but for the next two weeks I'm limited to lifting no more than
10lbs.  Almost everything I need is much heaver.  It has been a good while
since reading this forum and I had forgotten just how great the people on
this forum were so helpful, especially some one like me asking questions
that probably been covered here many times.  I'll search first and then ask
for help here.  Thanks to all. Charles

On Sat, Nov 24, 2012 at 8:55 PM, <jhowson4@xxxxxxxxxxx> wrote:

> Charles,
> I have been working on a coil like that for a while, but work is at a
> standstill due to lack of funding for tank capacitors.
> You are correct on the advantage, that you don't need a huge charging
> inductor which can be substituted for smaller air core units of a few mH.
> But to make it work really well you then need to use a filter capacitor,
> that way when the charging electrodes align, the tank cap can be charged
> nearly instantly. As the presentation time for the charging to occur is low.
> The other advantage to this approach is that you can use any spark gap bps
> you want. even those lower than the mains frequency, but only if you use
> the filter cap. My filter cap is a large array of microwave caps, it knocks
> the ripple after the rectifier down to less than 10%.
> You don't need a filter cap, but it really helps if you do, and this
> drives up costs more than an inductor. unless you acquire loads of
> microwave caps like i did on the cheap.
> For diodes the 1N5408 works really well in series chains. it has a 300A
> single impulse capability, and that reduces down to 30A at 400 Hz 3A DC. or
> so i'm told.
> Cheers,
> John "Jay" Howson IV
> "Why thank you, I will be happy to take those electrons off your hands."
> ----- Original Message -----
> From: "charles rakes" <crakes29@xxxxxxxxx>
> To: tesla@xxxxxxxxxx
> Sent: Saturday, November 24, 2012 4:46:19 PM
> Subject: [TCML] dc tesla coil
> I've been playing with Tesla coils since 1954 and about 12 years ago had
> started building a medium size coil with abt 1.5kw. I would now like to
> complete the coil. I would like to try making/using a RSG with one set of
> points to charge the tank cap and another set to discharge the cap. If
> this will work I should be able to really simplify the circuit. And not
> need chokes or other protection components. Will this approach work? If
> so I would try using a variable speed bench grinder as the basic of my
> RSG. Any help would be a greatly appreciated. Charles
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