Tim - Here is my take on spark gaps. First you say you have two gaps in
parallel, not series but parallel? Only one spark at a time can happen in a
parallel gap set up, maybe it will switch back and forth from one to the
other but only one at a time. A single gap can provide the least resistance
and more current in the primary circuit but does not quench and control
ring down very well. putting multiple gaps in Series seems to provide an
improvment in quenching and ring down control. To experiment with series
multiple gaps would seem to be a logical next step, two, four, maybe even
six gaps in series. A lot of people have had good results with the Richard
Quick multi gap and is not to difficult to construct. The next step up
would be a sucker gap, a lot of people like these and they give real good
results, there are examples on the net. But I believe the best and most
difficult is the Sync Rotary gap. my recommendation would be to experiment
with the progression of gaps above but keep an eye to words the sync
Rotary. Some thing I wish more people would do too, is cover your spark
gap, put a largish box over it to block the light from it and to quiet it
down a bit, doesn't have to be fancy, just a simple wooden box placed over
it wile your running. Nasty gasses build up inside but for the length of
time most of us run our coil it will be ok. For a 15kv NST the max voltage
it can handle is about 25kv +- a bit peak, so you want the largest cap you
can charge to 25kv. The Geek group capacitor chart is very good at
appropriate cap values for a type of setup/gap being used.
Thanks
David
On 4/7/2015 8:00 AM, Timothy Gilmore wrote:
David,
72" WOW as I have similar specs but only get 36-48" or so.
Here are my specs:
15kv, 120ma <-- Same (2 15kv 60mA NSTs)
3 levels of 0.010uf in parallel for 0.030uf mmc (30kv) <--- Seems like
your double of what mine is
2 parallel tungsten gaps "about" 1/4" separation each (with a squirrel
cage
fan blowing on them) <--- *Should these be tighter since there are 2 of
them? (i.e. 1/8" inch each)*
Secondary - 6"dia x 31"lg 1400 turns No. 24
Top load - 6" x 25" aluminum dryer ducting and foil pizza pans with foil
wrapped cardboard between and nylon toilet bolt <-- NOT wrapped in 3"
aluminum tape
(Would wrapping this improve the length significantly). I have the
materials for an 8" aluminum dryer ducting, aluminum tape, 17.75" x 1"
circular wood table (to be wrapped in foil and then glued and possibly
aluminum taped). *Should I just wrap the 6" more flimsy version or go with
the bigger 8" more solid heavier version (to construct) - OR use both on
top (wrapped/unwrapped in aluminum tape)?*
Primary 0.25" copper refrigerator coil in single layer tapped at 12.5
turns
I was thinking of the rotary gap motor version for the spark gap but have
no idea where to even start on this. I was hoping to get everything the
best I could first before and if I go down that route.
*So what has the greatest impact on spark length - the rotary spark gap or
the wrapped aluminum tape on the toroid - or are both necessary?*
Thoughts?
Tim
On Mon, Apr 6, 2015 at 8:56 PM, David <zipo@xxxxxxxxxxx> wrote:
Timothy, List - I too have recently put together a 15kv, 120ma coil. I'm
still tweaking for best out put. So far I'm getting 72" output and based
on
the way it was running and the way it was tuned I believe it will do at
least 80" after it's fully peaked. I can only run outside so I'm having
to
wait for good weather.
Here is a brief over view:
15kv, 120ma
.0625uf mmc
sync rotary gap @ 120 breaks/sec
secondary - 7"dia x 27.3"lg 1500 turns No.26 wire
Top load - 5" x 20" spun aluminum toroid
primary - 10 turn 2 layer spiral
Tesla equi drive circuit.
There are two aspects of tuning and peaking that seem not to get the
attention that they should (in my opinion).
First is that if tuning with a signal generator and a oscilloscope you
need to simulate the added capacitance of the spark. Adding a piece of
wire
the length of the spark your expecting to the top load and then tune with
sig gen and o scope. This seems to be overlooked a lot. Java TC shows
this
very well. If you ad an additional cylindrical top load, on JTC, .02dia x
length of spark (JTC will point it straight up) you will see a marked
reduction in res. frequency.
Second is that the safty gap or static gap width has a large impact on
output. There are way of setting these gap for safest operation. However
I'm guessing these gap widths get pushed a bit by savvy coilers but don't
talk about it. At least on a sync rotary safety gap width has a big
bearing
on output. I would find it very interesting to hear what gap width people
are using with what setup. And in full disclosure :) I have set both of
my
safety gaps at .22 using rounded brass draw pulls for electrodes.
It just seems to take a lot of time to get every thing tweaked to
Perfection.
Carry on
David
On 4/6/2015 9:34 AM, Timothy Gilmore wrote:
Has anyone put together any sort of a listing of others Tesla Coils
built
with parameters listed such as:
(for example): I have 2 NSTs (15kv, 60ma) each, 6" diameter, 31" high
secondary, torroid is ....
I am getting 3-4' sparks and wondering if I should be getting longer
sparks. Is this normal? or should I add another NST or bigger Toroid
(working on an 8" diameter ducting bigger one). How do I know since the
Tesla Map software says I should get "ideally" 72.6 inch sparks and I'm
getting about 1/2 to 2/3 of that. Just wondering if it's not tuned
properly
(but I think it is) - or making a larger toroid is worth the effort if
I'll
gain a foot or more sparks.
How does one know they are getting close to the best they can get in
spark
length?
I have attached my Tesla Map file of current settings.
Thanks,
Tim
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