Re: [TCML] RE: longer sparks?

[Gary Lau <glau1024@xxxxxxxxx>]

I would second Scott's comments.

The quality of the RF ground matters little towards spark length.  It mostly
affects how much RF enters your AC wiring.  I think AL foil is just as good
as any other similar-sized material; it's just more fragile.

I think your top load is definitely on the small side for your power level.
I've found that bigger is always better for top load and secondary coils.
Unfortunately changing these things have repurcussions throughout your coil
and a total makeover may be needed.

Spark gap design is very important.  I've never tried a MOT coil but the
high current levels here put additional demands on a static gap, and I think
that RSG's are more commonly used with MOT's for that reason.  If you are
using a static gap, the electrodes need to be very heavy with efficient
forced air cooling (sucker gap).

Regards, Gary Lau
MA, USA

On Sat, Mar 12, 2011 at 11:38 PM, Scott Bogard <sdbogard@xxxxxxxxx> wrote:

> Etienne,
>        I've found like many others here that spark gap and top load are
> infinitely important to a well functioning coil.  Grounding is not so
> important to performance, as it is to coil longevity (transformers will
> break down from RF injected into the supply) and of course the safety of
> electronics on the other end of the line.  An ARSG should help a lot, John
> Freu figured out a formula of how to size your top load, it is approximately
> .5 - .9 * SQRT of input watts = capacitance in pF for best performance, this
> is likely based in part off of the "standard" geometries we use (4.5/1
> ratio, 1000-1500 turns, etc...)  Just my two cents, others should have
> proper advice like gap designs etc.
>
> Scott Bogard.
> http://bogard.110mb.com/TeslaCoil.htm
>
>
> On 3/12/2011 8:06 PM, Etienne Dreyer wrote:
>
>>
>> Hi gang,
>> I've just completed a coil, but am not getting the spark lengths that I
>> expected. I am only getting weak 20" max, whereas I saw from sites like
>> loneoceans and greg's garage tesla that TCs very similar to mine easily make
>> 3ft and beyond. Could you guys give some suggestions on what I could do to
>> get longer sparks? Here are some of my specifications:
>> It is tuned
>> Dual mot with voltage doubler
>> 4" x 18" (actual coil length) secondary wrapped with 26AWG
>> 10 turn primary
>> 45nF @ 20KV capacitor
>> It is not well grounded- simply a sheet of aluminum foil on the ground
>> It does not have a very large toroid - 3" air duct with diameter of 13"
>> Single static spark gap (I'm going to upgrade to a ARSG)
>> Could the latter three issues be making such a big deal?
>> Very much appreciated,
>> Etienne
>>
>>
>>
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